On the Verifiability of Evolutionary Psychological...

On the Verifiability of Evolutionary Psychological Theories:An Analysis of the Psychology of Scientific Persuasion

Lucian Gideon Conway, IIIDepartment of PsychologyIndiana State University

Mark SchallerDepartment of Psychology

University of British Columbia

Evolutionary psychological theories have engendered much skepticism in the mod-ern scientific climate. Why? We argue that, although sometimes couched in the lan-guage of unfalsifiability, the skepticism results primarily from the perception thatevolutionary theories are less verifiable than traditional psychological theories. Itis more difficult to be convinced of the veracity of an evolutionary psychologicaltheory because an additional layer of inference must be logically traversed: Onenot only has to be persuaded that a particular model of contemporary psychologi-cal processes uniquely predicts observed phenomena, one must also be persuadedthat a model of deeply historical processes uniquely predicts the model of psycho-logical processes. This analysis of the psychology of scientific persuasion yields anumber of specific suggestions for the development, testing, and discussion of evo-lutionary psychological theories.

New theoretical perspectives in science are not borneasily. The broad notions and odd angles of novel ideasmove haltingly through cognitive passageways thathave been worn to the size and shape of conventionalwisdom. This difficult birth can be followed by a pain-ful childhood. Novel perspectives almost always meetsome sort of skeptical resistance, and even the mostuseful theoretical ideas must sometimes—like newkids in school—endure harsh challenges and criticalrebukes before they are eventually accepted on the in-tellectual playground.

This perspective is worth keeping in mind whenconsidering the recent emergence of evolutionary psy-chology—the metatheoretical perspective that appliesevolutionary biological thinking to psychological phe-nomena. Not surprisingly, evolutionary psychology hasprecipitated a considerable amount of scholarly debate.During the relatively short period of time that evolution-ary thinking has existed on the landscape of the psycho-logical sciences, it has been enthusiastically criticizedand has been defended with equal ardor. Although manycomplex issues are obscured by the sound and fury of

these scientific squabbles, one thing is clear: Evolution-ary psychological perspectives are difficult for manypsychologists to swallow whole.

Why is this? Critics of evolutionary psychologymight argue that the reasons lie in the contents of evolu-tionary thinking.Proponentsofevolutionarypsychologymay be tempted to believe that the reasons lie in theheads of the critics. Neither reaction is entirely true, norentirely false. When one separates wheat from chaff inthe harvest of criticisms and rebuttals, it becomes appar-ent that evolutionary psychological theories have a dif-ferent logical structure than most other psychologicaltheories and that these differences in logical structurehave important influences on the psychological pro-cesses that guide scientists’ appraisals of the theories.Our purpose in this article is to examine this subtle inter-action between the logic of evolutionary psychologyand the psychologic of scientists.

In doing so, our goals are twofold. At a broad, gen-eral level, we hope to illuminate the often overlookedbut fundamental role that psychological inference andpersuasion processes play in determining scientists’evaluative impressions of any hypothesis or theory inthe psychological sciences. More specifically, we at-tempt to apply this set of principles constructively tothe case of evolutionary psychology. We summarizeimplications specific to evolutionary psychologicaltheories in the hope that theories within this domainmight be articulated in such a way that they morefully—and less painfully—realize their potential. The

Personality and Social Psychology Review2002, Vol. 6, No. 2, 152–166

Copyright © 2002 byLawrence Erlbaum Associates, Inc.

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The writing of this article was partially supported by a grant toMark Schaller from the Social Sciences and Humanities ResearchCouncil of Canada. The authors thank Doug Kenrick and VirgilSheets for helpful comments on a prior draft of this article.

Requests for reprints should be sent to Lucian Gideon Conway,III, Department of Psychology, Root Hall, Indiana State University,Terre Haute, IN 47809. E-mail: [email protected]

considerations presented here are relevant not only tothe debate about evolutionary psychological theoriesin general but also to the social psychological commu-nity in particular. Given the logical necessity of repro-duction to the passing on of one’s genes, it is perhapsunsurprising that much attention within evolutionarypsychology has been paid to human mating behavior(e.g., Buss, Haselton, Shackelford, Bleske, & Wake-field, 1998). This focus on such an obviously socialphenomenon has put social psychological research onor near center stage for much of the debate relevant toevolutionary psychological theories. Thus, althoughthe ideas described in this approach are applicable be-yond the walls of social psychology, in choosing illus-trative examples we have kept our focus on theoriesthat are decidedly social in nature.

Scope of This Article

In this article, we attempt to identify one particularset of reasons why people are skeptical of evolutionarytheories. That set of reasons focuses on the logic of in-ference that is applied to specific theories and the sub-sequent impact of that logic on the psychology of sci-entists. We recognize, however, that many processesoutside of those that we discuss also impact the persua-siveness of evolutionary psychological theories. Forexample, scientists think the probability that a particu-lar metatheoretical perspective will yield a true theoryor hypothesis is greatly influenced by the perceptionthat the perspective has previously yielded true hypoth-eses. Thus, there is a cumulative effect of positive re-sults for a given theoretical perspective: To the degreethat scientists perceive that evolutionary psychologicaltheories in general have had success, they are morelikely to perceive specific new evolutionary psycho-logical theories to be true (see Ketelaar & Ellis, 2000).However, these and other processes, although impor-tant, fall beyond the scope of this article.

What Do Scientists Want?

To understand the processes underlying the evalua-tion of theories in evolutionary psychology (and theo-ries in other domains as well), it is necessary to con-sider the context within which those theories are eval-uated. This context is defined by the goals of scientists(Crandall & Schaller, in press; Kitcher, 1993; Krug-lanski, 1994). Scientists seek to discover the facts ofreality, to provide true explanations for those facts, andto use those explanations to accurately predict newfacts. Given these goals, scientists value veracity—inthe form of empirical certification—above all else(Merton, 1942). In fact, among many philosophers of

science, the term knowledge itself implies veracity(Bechtel, 1988).

Given this fundamental value, scientists are prag-matic in choosing the standards against which theoriesare judged. The gold standard is the extent to which thestatements in theory provide accurate representationsof reality. First and foremost, we ask this questionabout any theory: “Is it true?”

Issues of Falsifiability and Falsification

The positivist philosophy that guides psychologi-cal science informs us that we can never answer thisquestion—“Is it true?”—in the affirmative, only inthe negative (Popper, 1959). We can never claim with100% certainty that a theory is true, but we can some-times confidently reject a theory as false. It is for thisreason that falsifiability is a necessary feature of anyscientific theory. Nonfalsifiable statements may wellbe true, of course, but observations of reality are notdiagnostic of their truth. Consequently, for individu-als whose goal is the determination of truth, nonfalsi-fiable statements are—for good reason—dismissed asscientifically irrelevant.

Falsifiability of EvolutionaryPsychological Theories

There is a long history of lodging charges of non-falsifiability against evolutionary thinking in the bio-logical sciences (Peters, 1976; Popper, 1959). Thesame charges have been leveled against applicationsof evolutionary thinking in the psychological sciencesas well (e.g., Gould, 1997; Kitcher, 1985). Are thesecharges valid? Are evolutionary psychological theo-ries nonfalsifiable? No. As others have taken pains toarticulate (e.g., Kenrick & Simpson, 1997; Ketelaar& Ellis, 2000), theories and hypotheses developedwithin evolutionary psychological frameworks are ex-actly as falsifiable as any other theory or hypothesisin psychology.

To illustrate, consider two different theoretical struc-tures within psychology. The first is an evolutionarypsychological model specifying the evolutionary pres-sures attendant on differential parental investment inchildbirth within ancient populations (e.g., Buss &Schmidt, 1993). This model suggests that in ancientenvironments it would have been advantageous (withrespect to gene survival) for men to focus on findingmates that were maximally fertile, whereas it wouldhave been advantageous for women to focus on findingmates that were best able to provide resources for theirchildren. The model further suggests that, because ofthese differential selection pressures, men would havedeveloped a different set of psychological cues formate preferences than women: Men would be likely to

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focus on cues relevant to fertility, whereas womenwould have developed a set of cues relevant to resourceprovision. The second model is a social structural mod-el specifying different contemporary cultural normsand expectations operating on men and women (e.g.,Eagly & Wood, 1999). This model suggests that, be-cause of discrepancies in gender status, men haveadopted dominant social roles, whereas women haveadopted (or been subjected to) subordinate social roles.The model further suggests that, given this presentstate of affairs, it is advantageous for men to seekmates that are best able to fill subordinate social rolessuch as housekeeping, whereas it is advantageous forwomen to seek mates that are best able to provide di-rect resources to them (as they cannot get those re-sources themselves).

Through the process of logical deduction, both theevolutionary and social structural theories outlinedpreviously yield an identical hypothesis: In general,men prefer younger women for mating partners,whereas women prefer older men. Now suppose thatempirical evidence is collected that examines the rela-tion between gender and the preferred age of matingpartners, and suppose that this evidence reveals no re-lation whatsoever. As long as this non-effect cannot beeasily attributable to shoddy measurement, it bearsnegatively on the hypothesis; therefore, it bears nega-tively on all theoretical structures that logically yieldthat hypothesis. Just as the model specifying contem-porary cultural norms would be empirically falsifiedby this non-observation, so too—and to an equal ex-tent—would the model specifying evolutionary pres-sures be empirically falsified.1 Clearly, then, skepti-cism accorded to evolutionary psychological theoriesdoes not result from the logic of falsifiability (Schaller& Conway, 2000).2

Falsification of EvolutionaryPsychological Theories

Although a theory must be falsifiable to be consid-ered a scientific theory, the falsifiability of a theory it-self has almost no bearing whatsoever on the extent towhich that theory is judged to be true. Logically (ac-cording to the positivist philosophy that most psycho-logical scientists ascribe to), assessments of truth arebased not on falsifiability but the results of exposure tofalsification: To what extent has a theory survived ac-tual exposure to empirical observations that are diag-nostic of that theory’s accuracy? If an observationmatches the predictions deduced from the theory, thenthe theory survives that exposure. The more exposuressurvived, the more the theory is perceived—howevertentatively—to be true.

Is it possible that theories in evolutionary psychol-ogy are greeted with special skepticism because thesetheories are—compared to other theories in psychol-ogy—underexposed to opportunities for falsification?Perhaps this is true. Given the relative youth of evolu-tionary psychology, there are a number of novel theo-ries within the domain that have not yet had the op-portunity to be extensively tested against empiricalobservations. For these untested theories, scientists ad-hering to a positivist approach should logically main-tain some skepticism.

On the other hand, this state of affairs is no differentfrom that in any other domain of active psychologicalinquiry. Although there are some evolutionary psycho-logical theories that are just beginning to be tested em-pirically, there are others that have survived exposureto numerous opportunities for empirical disconfirma-tion. Consider, for example, theories based on evo-lutionary models of differential parental investment(Buss & Schmidt, 1993). These theories have receivedby far the most empirical attention of any theoreticalstructures within the domain of evolutionary psychol-ogy and have survived dozens—if not hundreds—ofindependent exposures to falsification (Buss, 1989;Buss & Schmidt, 1993; Gangestad & Simpson, 2000;Kenrick & Keefe, 1992). Yet, curiously, it is within thecontext of these theories that charges of nonfalsifi-ability and other declarations of disbelief are most of-ten aired. Thus, it seems unlikely that underexposure todiagnostic data accounts for the skepticism that chroni-cally greets theories in evolutionary psychology.

Why Does the Skepticism Persist?

Apparently, something other than the positivist log-ic of falsification underlies skepticism about theoriesin evolutionary psychology. So why does the feelingpersist that evolutionary psychological theories are

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1Of course, falsification of a theory is rarely, if ever, based on asingle negative result, but rather depends on an accumulation of neg-ative results. It is an inferentially complex passage from an “empiri-cal disconfirmation” to the full falsification of a theory (Greenwald& Ronis, 1981; Laudan, 1977; Quine, 1953).

2The falsifiability charge may partially rest on a confusionabout what an evolutionary theory actually is. Consider again theevolutionary theoretical statement that “differential selection pres-sures for men and women led to differential rates of promiscuity inmen and women.” As discussed previously, this statement, taken asa whole, is completely falsifiable: If men and women do not havedifferential promiscuity rates, then it is clear that differential selec-tion pressures did not lead to differential promiscuity rates. How-ever, evidence that men and women do not have differential pro-miscuity rates does not mean that the hypothesized differentialselection pressures did not exist. The key distinction is that evolu-tionary theories of psychology do not hypothesize that “certainevolutionary pressures existed;” rather, they hypothesize that “cer-tain evolutionary pressures led to certain psychological structures.”The first statement cannot be falsified by psychological studies; thesecond statement can. It is the second statement that evolutionarypsychological theories are making.

less falsifiable—or perhaps just less true—than othertheories in psychology?

One possibility that is commonly asserted (atleast informally) by advocates of evolutionary psy-chology is that skeptics are merely undereducated—that they are not yet well informed about either theactual nature of evolutionary psychological theoriesor about the wealth of diagnostic evidence that sup-ports those theories. This explanation implies thatevolutionary psychological theories are no differentthan any other theory in psychology and that as peo-ple become more familiar with the actual structureof evolutionary theories and the considerable empir-ical literature bearing on those theories, the skepti-cism feelings will disappear.

This explanation probably has at least some merit;lots of psychologists (and many more people outsidethe field) remain only vaguely aware of the contentsof scientific inquiry within evolutionary psychology.However, we suspect this explanation is incompleteand its implication is overly optimistic.

Close attention to the underlying logical structure oftheories in evolutionary psychology reveals that thesetheories are, in some important ways, different frommost other theories in psychology. Moreover, regard-less of any ostensible adherence to a positivist philoso-phy of science, the process through which individualsbecome persuaded as to the truth of a theory has little todo with the strict logic of falsification (Schaller &Conway, 2000). By attending to the interaction be-tween the logical structure of evolutionary psychologi-cal theories and the psychological processes underly-ing individuals’ assessments of those theories, we canmore completely understand the origins of the skepti-cism that greets evolutionary psychology. This analy-sis also yields a number of implications and sugges-tions pertaining to the manner in which evolutionarypsychological theories might best be constructed, test-ed, and discussed.

Inferential Logicof Scientific Persuasion

Human beings—including scientists—are intuitiveverificationists, not intuitive falsificationists. As hu-mans, we do not care very much for what is not; weonly really care for what is (Schaller & Conway, 2000).Scientists are persuaded as to the accuracy of a theorythrough an intuitively appealing logic: We believe thata theory is true if (a) empirical results match the predic-tions of the theory and (b) these empirical results can-not obviously be explained otherwise. Scientists’ ex-perimental methodologies are fueled primarily by thislogic. To the extent that obtained empirical results re-flect positively on a focal theory and cannot obviously

be explained otherwise, the focal theory is judged (ten-tatively) to be true.3

Of course, as scientists we do not typically comparetheories directly to empirical data. We judge the verac-ity of theories only after first judging the veracity ofhypotheses deduced from those theories. To under-stand the inferential logic through which scientists arepersuaded as to the truth of a theory, we must first con-sider the inferential logic through which we are per-suaded as to the truth of a hypothesis.

Perceived Truth of a Hypothesis

The confidence in the truth of any hypothesis is basedon answers to two questions: (a) Just how well do the ob-servedempirical resultsmatchupwith theconceptualhy-pothesis? and (b) just how easily can these same empiri-cal resultsbeaccountedforbyalternativeexplanations?

The first of those judgments is informed by a vari-ety of distinct factors: patterns of obtained experi-mental results, effect sizes indicated by those results,construct validity of experimental operations, and soforth. Considered together, these factors yield a sub-jective judgment. It is possible to imagine this judg-ment being made on a sort of “batting-average” scaleanchored by endpoints 0 (no correspondence) and 1(perfect correspondence).

The second subjective judgment—presence of via-ble alternative explanations—is also informed by a va-riety of distinct considerations: statistical results ofnull hypothesis testing, internal validity of experimen-tal methods, and the awareness of other logically plau-sible conceptual hypotheses predicting the same pat-tern of results. Considered jointly, these factors yield asubjective judgment that also might be represented ona scale anchored by endpoints of 0 (complete absenceof alternative explanations) and 1 (certainty that alter-native explanations account for the observed results).

This intuitively appealing logic can be formallyexpressed by a simple linear equation. Let A repre-sent the extent to which empirical results persuade usas to the veracity of the focal conceptual hypothesis.Let a represent the first judgment (correspondence be-tween conceptual predictions and empirical results)and a′ represent the second judgment (plausibility ofalternative explanations).

A = a * (1 – a′) (1)

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3This intuitive logic of scientific inference is not dissimilar fromthe intuitive logic through which we judge the causes of observedevents in our everyday lives (Bem, 1972; Kelley, 1967). More gener-ally, the simple model of inferential logic outlined here is consistentwith a more sophisticated model of “explanatory coherence” rele-vant to both scientific and everyday inference (Kunda & Thagard,1996; Thagard, 1992).

Thus, the perceived veracity of a focal conceptualhypothesis is the multiplicative function of the per-ceived empirical support for the hypothesis and the in-verse of the perceived plausibility of some alternativeexplanation(s) for that apparent support.4

Perceived Truth of a Theory

Of course, scientists think not only in terms of sin-gle assertions expressed as hypotheses, but also interms of coherent clusters of assertions in the form oftheories. Theories are at least one logical step re-moved from hypotheses tested by empirical methods.The typical theory in psychology consists of a set oflogically connected statements concerning the opera-tions of some set of psychological processes. Thesetheoretical statements imply—through a process oflogical deduction—a set of specific hypotheses aboutthe relations between specific variables. Each of thesehypotheses is subject to empirical test through thelogical process described previously. However, sup-port for a specific conceptual hypothesis does notguarantee the subjective persuasiveness concerningthe veracity of the theory from which it is deduced.This is because no conceptual hypothesis can be as-sumed to be deducible solely from that one theory. Itis always possible (and highly likely) that the sameconceptual hypotheses might be deduced from one ormore different theoretical structures. Thus, given per-ceived empirical support for a focal hypothesis, theperceived veracity of a theory of psychological pro-cesses depends on two judgments: (a) the extent towhich that hypothesis is logically deduced from thetheory and (b) the extent to which it cannot be logi-cally deduced from alterative theories.

The first of those judgments is based on a subjectiveassessment of the tightness of the logic through whichthe hypothesis is deduced from the focal theory. Thesecond of those judgments is based on a subjective as-sessment of the logical ease through which the samehypothesis is deducible from alternative theories.

For the sake of formal expression, both judgmentsmight be represented on 0 to 1 scales and may be sym-bolized, respectively, as b and b′. The extent to which aparticular empirical result persuades the observer as tothe veracity of a particular theory (B) must take into ac-

count not just the judgments symbolized by a and a′but also these new judgments b and b′:

B = [a * (1 – a′)] * [b * (1 – b′)] (2)

For most theories in psychology, the logic of in-ference ends there. That is because most theories inpsychology simply specify the operations of psycho-logical processes—the causal relations betweenmore or less contemporaneous variables. Yet sometheories go further.

Some theoretical perspectives within psychologyarticulate not only conceptual models describing thecontemporary psychological operations but also artic-ulate models describing the historical origins of thosepsychological operations. For instance, one social roletheory of gender differences identifies a set of long-agohistorical origins of contemporary sex-linked divisionsof labor (e.g., Eagly & Wood, 1999). As another exam-ple, terror management theory yields many testable hy-potheses about contemporary psychological phenom-ena as a consequence of first articulating a set ofhistorical processes through which cultural norms andself-esteem systems emerged (Greenberg, Solomon &Pyszczynski, 1997; Solomon, Greenberg, & Pyszczyn-ski, 1991). Additionally, of course, all theories withinevolutionary psychology specify historical modelswithin which the evolutionary origins of contemporarypsychological events are described. Evolutionary theo-ries of contemporary human mating behavior (e.g.,Buss & Schmidt, 1993; Gangestad & Simpson, 2000)not only specify the particular ways in which men andwomen differ in their approaches to sexual relation-ships, they also specify the evolutionary mechanismsthrough which these differences emerged long ago.Evolutionary theories of contemporary human cogni-tion (e.g., Cosmides, 1989; Gigerenzer, 1998) not onlyspecify (just like most other psychological theories)the presence of specific cognitive operations and theeffects of contextual cues on those cognitive opera-tions, they also specify (unlike most other psycho-logical theories) the evolutionary mechanisms throughwhich these cognitive systems emerged in the firstplace, long ago.

Thus, these theories contain two distinct models,not one, and these models address very different typesof questions (Conway, 1999; Ketelaar & Ellis, 2000;Schaller & Conway, 2000; Simpson & Gangestad,2001). Even if one accepts as true the theoretical state-ments that specify contemporary psychological opera-tions and events, this does not necessarily mean thatone accepts as true the statements specifying the his-torical origins of those operations and events. An addi-tional layer of inference is introduced that bears astructure identical to the two layers of inference sum-marized previously. Persuasion concerning the verac-ity of some specific theoretical model of origins is a

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4These simple considerations reveal why falsification plays sucha minor role in actual scientific persuasion. A conceptual hypothesismay correspond exactly to a set of empirical results (and thereforeresist falsification) but may still be believed with little confidence be-cause of the presence of other, equally plausible, explanations. Simi-larly, difficulties in operationalizing conceptual variables may makeit difficult to empirically falsify a conceptual hypothesis (Quine,1953), but this does not mean the hypothesis is viewed as true. It isquite the contrary: The same operational difficulties interfere withthe ability to obtain support for the hypothesis, and this is what reallymatters in scientific persuasion.

function of two considerations: (a) the extent to whichthe model of contemporary psychological processes islogically deduced from the historical model of originsand (b) the extent to which it cannot be logically de-duced from alternative models specifying distinctlydifferent historical origins.

The first of those judgments is based on a subjectiveassessment of the soundness of the assumptions andthe tightness of the logic through which the model ofcontemporary psychological events is deduced fromthe model of historical (e.g., evolutionary) origins. Thesecond of those judgments is based on a subjective as-sessment of the logical ease through which the sameset of psychological events is deducible from alterna-tive models of historical origin.

As mentioned previously, both of these judgmentsmight be represented formally on 0 to 1 scales andsymbolized, respectively, as c and c′. The extent towhich a particular empirical result persuades the ob-server as to the veracity of a particular theory of ulti-mate origins (C) must take into account not just thejudgments symbolized by a, a′, b, and b′, but also thesenew judgments c and c′:

C = [a * (1 – a′)] * [b * (1 – b′)] * [c * (1 – c′)]. (3)

Summary

Figure 1 presents schematically the formal logicjust outlined. This schematic makes the fundamental

point very clear: The more inferentially distal a theo-retical model is from empirical results, the more dif-ficult it must be to persuade people that the elements ofthat model are accurate. Only two sets of logical con-siderations (a and a′) influence one’s confidence in aspecific conceptual hypothesis. Two additional consid-erations have the potential to dampen the confidenceone has in the veracity of a theory about psychologicalevents, and then two more considerations may dampenconfidence in the veracity of a theory about the histori-cal origins of those psychological events.

Implications for Theoriesin Evolutionary Psychology

It is with this logic of scientific persuasion in mindthat we can appreciate why it is considerably harder forpeople to be persuaded about the veracity of sometypes of psychological theories compared to others.There are simply more obstacles to persuasion for the-ories with a historical model. These are not merely psy-chological obstacles that lie entirely within the headsof critics; rather, they are legitimate logical obstacles tothe inference process. Some of these obstacles to per-suasion apply across many different types of theoriesthat specify models of the historical origins of psycho-logical processes (including both evolutionary and so-ciocultural theories); other aspects apply more unique-ly to evolutionary psychological theories.

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Figure 1. A schematic model of logical inference processes underlying scientific persuasion.

Inferential Obstacles Facedby All Theories Specifying Modelsof Historical Origin

Multiple layers of inference. Consider againthe example of gender differences in the preferred ageof mates. Recall that the logic of falsification is suchthat if empirical evidence indicates no gender differ-ences, then this evidence reflects equally negatively onall theories that predict such a difference—regardless ofwhether the theory specifies merely contemporary psy-chological processes or whether it specifies a historicalmodel as well. However, what if the evidence revealsthe predicted difference that men do indeed preferyounger women for mates, whereas women preferolder men. This positive evidence does not reflectequally on the different statements that logically implythis result. The more levels of inference that a predic-tive structure is removed from the results, the less per-suasive those results are about the truth of that predic-tive structure. The likelihood is perhaps only modestthat a person will confidently be persuaded that oneparticular model of psychological events must be cor-rect. The likelihood is smaller still that a person will bepersuaded that one particular model of historical ori-gins must be correct. This example illustrates a funda-mental point: Psychological theories specifying mod-els of historical origins are, in general, more difficult toswallow whole than theories specifying only models ofcontemporary psychological events.

It is obvious from the model presented in Figure 1that even if all levels of a historical theory maintain arelatively high batting average, the multiplicative ef-fect of swallowing all three levels can still be quite low.As an illustrative example, suppose at every level of in-ference the logical consistency scores (represented bya, b, and c) are .7 and the probabilities associated withalternative explanations (represented by a′, b′, and c′)are only .1. In spite of the persuasive probabilities thatexist at of each level alone (e.g., A = .7 * (1 – .1) = .63),the compound probabilities multiplied across all threelevels is much lower (C = .63 * .63 * .63 = .25). Thus,even in the face of fairly convincing evidence predictedby the theory, the extent to which the whole theoreticaledifice is perceived to be verified is still quite low.

This illustrates the difficulty faced by psychologicaltheories that specify models of historical origin. Evenif everything is generally logically compelling acrossthe different levels of theory, it is difficult for scientiststo feel confident that a result reflects the consequencesof the historical processes specified by the theory.

Assumptions about historical circumstances.Psychological theories have the logical structure of

a set of “if–then” statements (“If A then B,” “If B thenC,” “If C then D, E, and F”) that are deducible fromsome stipulated set of initial assumptions. A first step

in judging the plausibility of a theory is an assessmentof the assumptions on which it is based. If the assump-tions are of questionable veracity, then the entire theo-retical structure is likely to be judged implausible.

Theories describing contemporary psychologicalprocesses typically begin with assumptions that areeasily observed and readily granted to be true. For ex-ample, no one really doubts the initial assumptionsfrom which cognitive dissonance theory is derived(e.g., that individuals sometimes are subject to con-flicting cognitions; Festinger, 1957). On the otherhand, theories describing historical origins of psycho-logical processes begin with assumptions about struc-tures, events, or processes pertaining to the past (e.g.,Cosmides, 1989; Eagly & Wood, 1999; Greenberg etal., 1997). The past is less easily observed than thepresent and so the veracity of these assumptions is lessreadily granted. Therefore, compared to the logicalplausibility accorded explanations based purely oncontemporary psychological processes (symbolized byb in the preceding equations), the logical plausibilityaccorded historical explanations (symbolized by c) islikely to be somewhat lower.

Alternative historical explanations. In addition,the perceived likelihood that alternative hypotheses ortheories can explain a given result will almost certainlyincrease as one moves across the hypothetical, psycho-logical, and historical levels (from A to B to C in Figure1). The confidence with which persons feel like they canrule out alternative hypotheses at the hypothesis-testinglevel (a′) is frequently quite high. At this level, the toolsthat aid people in ruling out alternative explanations(e.g., inferential statistics, experimental design) are rel-atively sophisticated. When applying this same logic atthe level of psychological theories (b′) the task is moredaunting. When scientists ask what models of psycho-logical processes might yield a specific conceptual hy-pothesis, we often open a broad door through whichmany different theoretical structures can pass. Conse-quently b′ is typically accorded a higher value than a′.

Now consider theoretical structures that pertain tothe historical past. Ruling out alternative explanationsat the historical level (c′) is typically far more difficultthan merely ruling out alternative explanations at thelevel of contemporary psychological events (b′). Thereare several reasons for this added difficulty. First, thereis the issue of the temporal gap between cause and ef-fect. Historical theories typically indicate some con-siderable passage of time between the proposed causalevents (e.g., adaption pressures, the origins of socialsystems) and the psychological structures that thoseevents are purported to give rise to. Thus, there is al-ways plenty of time for other unidentified events orprocesses to give rise to the same structures. Second,there’s the pragmatic difficulty of devising empiricalmethods that might actually comment on alternative

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explanations at the historical level (Conway, 1999;Lewontin, 1990; Richardson, 1996, 2000). It is diffi-cult to employ psychological research methods to mea-sure variables or processes purported to operate in thepast. In the absence of empirical evidence, commen-tary on alternative explanations is limited to logicalconsiderations alone (such as parsimony; see Archer,1996, and Schmidt & Buss, 2001 for examples).

Thus, not only do historical theories in psychologyhave to bear the weight of the cumulative impact ofmany layers of inference, they also have to deal withthe fact that this last layer of inference—pertaining tomodels of historical origins—is by itself an exceed-ingly tough sell.

Extra Inferential Obstacles FacingEvolutionary Psychological Theories

Even among the small set of psychological theoriesthat describe a model of historical origins, there is con-siderable variability. Some of these theories are morelikely than others to arouse skepticism, suspicion, andcharges of being unfalsifiable. Some, more than others,resist being swallowed whole. For instance, there areseveral distinct theories that describe historical originsof gender differences in sexual behavior—some with astrong evolutionary component (e.g., Buss & Schmidt,1993) and some without (e.g., Eagly & Wood, 1999). Itappears that people are more resistant to persuasion byevolutionary psychological theories than they are toother models of origins. Why is this? An answer de-mands attention to three dimensions along which evo-lutionary psychological theories typically differ fromother theories of origins.

Temporal remoteness of specified origins. Al-though all historical theories suffer inferentially be-cause they are set in a past that is no longer directly ac-cessible, there is considerable variability in how farback in time these theories reach. Some models specifycausal events that occurred in relatively recent history,whereas others specify events that occurred in themuch more distant past. For instance, one prominentsocial roles theory of gender differences (Eagly, 1987;Eagly & Wood, 1999) specifies that the origins of con-temporary gender roles lie in historical events that areassumed to have occurred during the relatively briefand recent period of history since Homo sapiens ap-peared on the global scene. In contrast, theories speci-fying the evolutionary consequences of differential pa-rental investment (Buss & Schmidt, 1993; Gangestad& Simpson, 2000) describe events that are assumed tohave occurred during a more temporally remote epochof history that predates the appearance of Homo sapi-ens. Thus, although both of these kinds of models areset in the past, the evolutionary model is more greatlyremoved from contemporary psychological processes.

This fact makes the linkage between the historicalmodel and the contemporary model seem to be a muchbigger and less straightforward deductive step. The dif-ficulty in persuading individuals as to the veracity ofmodels pertaining to the past is greater as those modelsdip more deeply into the past. The assumptions onwhich evolutionary models are based (biological char-acteristics of prehuman populations, the physical andsocial environments governing early hominid life,etc.), are based on inevitably spotty, inevitably imper-fect clues about that very distant past (e.g., Tooby &DeVore, 1987; Wrangham, 1987). In addition, theamount of time passed between a putative cause and anostensible effect almost certainly serves as a heuristicindicating the likelihood that alternative historical the-ories can account for specified psychological struc-tures. Because evolutionary models of origins are setso far in the past, there is much more time for otherkinds of processes—such as sociocultural processes—to have had an impact on our psychology (e.g., Scher,1999; Wood & Eagly, 2000).

In addition, as the temporal distance between ori-gins and outcomes grows, it is less easy to convinceskeptics that empirical evidence could possibly be col-lected that uniquely supports the specified link be-tween historical and psychological structures. It is per-haps not unreasonable to entertain the hope that con-temporarily available evidence (e.g., written historiesor other cultural artifacts) might be found that reveals ahypothesized sequence of cultural events occurringwithin, say, the last 2 or 3 thousand years. It is a morefarfetched hope that contemporarily available evidencemight be found to reveal unambiguously a hypothe-sized sequence of evolutionary events occurring overthe course of tens of thousands of years of human his-tory. Moreover, one can relatively easily conceive ofmethodologies that, within a compressed contempo-rary time frame, might simulate the emergence of cul-tural norms over time (e.g., Arrow & Burns, in press;Latané & L’Herrou, 1996; Schaller & Conway, 1999;Sherif, 1936). It is far more difficult to concoct con-temporary methods that simulate—to any reasonabledegree of fidelity—the natural and sexual selectionprocesses hypothesized to underlie the emergence andevolution of human cognitive structures.

Complexity of the metatheoretical perspective.The more complex a metatheoretical perspective isperceived to be, the more likely that it will be perceivedto yield multiple alternative explanations that mightaccount for some observed phenomenon. All historicaltheories suffer inferentially because the historical pastis complex. It is suspected, however, that evolutionarytheories are especially likely to be affected by the per-ception of metatheoretical complexity.

The relation between biological adaptation process-esandpsychologicalprocesses isprobablyperceivedby

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most people to be more complex than the relation be-tween historical social structures and psychologicalprocesses. Evolutionary thinking suggests exception-ally complex processes—processes involving multifac-eted relations between genes, phenotypic characteris-tics, and environments. Because the relation betweenphenotypic responses and genetic survival is compli-cated, it is no easy logical task to figure out the specificpsychological traits that might have been adaptive in an-cient environments (Caporael & Brewer, 1995, 2000;Conway, 1999; Dawkins, 1976; Richardson, 2000). Thesameadaptiveproblemmaybesolved inmultiplediffer-ent ways; responses to very different adaptive pressuresmay result in very similar phenotypic consequences.This complexity confers uncertainty; working withinthe evolutionary metatheoretical framework, theoristsmay find multiple logically distinct ways of accountingfor a given phenomenon.

Even when no specific alternative theories are read-ily available, the complexity of the relation between be-haviors, genes, and survival may leave people with avague feeling ofmystery anduncertainty.Thismayheu-ristically compel a subjective sense that other historical(evolutionary or otherwise) theories might also yieldsimilarpredictions—even ifonecannot imagineexactlywhat those theories might be. Thus, even without clearchallengers to evolutionary theories, people may yetstill be uniquely skeptical of the ability to rule out alter-native theoretical explanations for these theories.

Relative size of history model within the theoret-ical framework. A third dimension of importancerefers to the relative size of the historical model withinthe context of the relevant theory (see Schaller & Con-way, 2000). Some theories that include historical mod-els articulate those models briefly as points of de-parture and devote the bulk of theoretical statements tothe articulation of contemporary psychological events(e.g., Eagly, 1987; Solomon et al., 1991). The relativesize of the historical model is small. In contrast, withinthe framework of most evolutionary psychological the-ories, the historical model is much more than a merepoint of departure. Indeed, the presence of a well-spec-ified historical model of origins is required for thattheory to be considered to fall within the domain ofevolutionary psychology. For this reason, within evo-lutionary theories of psychology, the relative size of thehistorical model is frequently large.

Relative size matters. As we have shown, it is com-paratively more difficult to be persuaded as to the ve-racity of a model of historical origins (Formula 3, pre-viously) than it is to be persuaded as to the veracity of amodel of psychological events (Formula 2). Therefore,the bigger the relative size of the historical modelwithin a larger theoretical structure, the more difficultit is to be persuaded as to the truth of that whole theory.

Where Do We Go From Here?

This analysis helps to explain why theories inevolutionary psychology are commonly viewed withgreater skepticism than more traditional psychologi-cal theories. These considerations, coupled with thefact that it is essential to be intellectually persuasiveto succeed in the scientific environment, might temptthe pragmatic scientist to play it safe—to avoid dab-bling in multilevel theories that specify models ofhistorical origins.

Giving in to this temptation, however, would surelyhave unhealthy consequences for the advancement ofpsychological science. There are already plenty of pres-sures on scientists to think small (Garcia, 1981; Hor-gan, 1996; Hull, 1988). Although there may be short-term personal advantages of a narrow epistemologicalapproach (e.g., one’s own ideas are less likely to be ma-ligned as wrong, and one can more confidently trustothers’ ideas as well), these are offset by a considerablescientific downside (e.g., vanishingly small inferentialreturns on empirical investment and stagnation of the-ory development). There is plenty of concern that thereis an increasing tendency toward this sort of epis-temological conservatism in psychology (Higgins,1992; Kruglanski, 2001; Schaller & Crandall, 1998;Wallach & Wallach, 1998); it’s important to fight offthe easy temptation to play it safe. Thinking big andworking with ambitious multilevel theories helps en-sure a healthier, more progressive science (Kenrick &Simpson, 1997; Solomon et al., 1991).

The constructive conclusion to draw from ouranalysis is this: Scientists need to continue to developambitious multilevel theories like those in evolu-tionary psychology, but we need to do it better. Thelogical and psychological considerations identifiedpreviously imply several practical guidelines towardarticulating evolutionary psychological theories thatare maximally persuasive.

Rigorous Specification of a Modelof Historical Events

As logical structures, scientific theories comprisesets of statements that follow from some initial set ofassertions. In the case of evolutionary psychologicaltheories, the assertions that form the conceptual start-ing point pertain to constraints operating on popula-tions long ago. The consequences of those constraints—specified in a model of historical events—occurredover a considerable stretch of time. If a theory is to beperceived as plausible, these initial assertions and themodel of historical events must be rigorously and be-lievably specified.

Because they pertain to circumstances existing inthe unobservable past, the believability of the asser-tions underlying evolutionary psychological theories

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rests on intuition or inference or both. Intuition aloneallows people to readily accept the supposition that thephysiological differences currently describing menand women must have existed for a very long time.Consequently, the considerable archeological and bio-logical evidence supporting that supposition is scarce-ly required to be convinced that differential parentalinvestment must have described immense chunks ofhuman history. (Given its immediate intuitive appeal, itis no surprise that this assertion has offered the startingpoint for so much work in the realm of evolutionarypsychology.) Not all assertions about the constraintsoperating on populations can be intuited with suchconfidence, however. Assertions about social struc-tures within ancient populations cannot be based on in-tuition alone. Any theory or model proceeding from anassertion about social structures during ancient epochsis unlikely to be fully persuasive unless intuition is sup-plemented with rigorous documentation attesting tothe plausibility of those assertions. Audiences need tobe apprised of relevant and credible anthropologicaland zoological evidence before they can be expected toaccept any assertion about the social structures of an-cient populations.

Documenting these initial assertions is merely thefirst step in articulating a plausible model of historicalevents. The next step is the rigorous specification of theevolutionary consequences of the asserted constraints.Many applications of evolutionary thinking to psy-chology skimp on this step—indicating merely that“Given constraint X, it makes sense that adaptive con-sequence Y would have occurred.” That may be true,but it is not logically convincing. Specific constraintsnever necessarily require some specific adaptive con-sequence; any of several other consequences mighthave been equally adaptive. The failure to attend to themultiple plausible consequences of any single con-straint can lead to the statement of a theory that—al-though logically falsifiable—may be easily dismissed.More compelling theories include more fully artic-ulated descriptions of the multiple constraints operat-ing simultaneously on human populations (e.g., socialconstraints as well as constraints posed by existing an-atomical structures) and more carefully explain whysome particular adaptive consequence was more likelyto emerge than other possible consequences.

To this end, it is important for evolutionary psychol-ogists to do thorough cost–benefit analyses to be maxi-mally persuasive. Historically, evolutionary scientistsin general and evolutionary psychologists in particularhave had a tendency to attend almost exclusively to po-tential benefits of a proposed adaptive trait while ig-noring potential costs (Gangestad & Simpson, 2000).Failure to engage in full cost–benefit analyses has atleast two negative consequences for evolutionary psy-chologists. First, because it is frequently easy for per-sons to imagine such costs for supposedly adaptive

traits (see, e.g., Conway, 1999), the skeptic may dis-miss a theory as soon as any unidentified cost of thehypothesized adaptation comes to mind. Thus, incor-porating potential costs of an adaptation into an evolu-tionary theory does not allow the skeptic this “easyout” and forces criticisms to be more fully articulated.Secondly, not considering both costs and benefits oftraits also forfeits the possibility of deducing morecomplex and novel hypotheses (see Gangestad & Simp-son, 2000). All seemingly adaptive traits have potentialcosts, and analysis of those costs is probably morelikely to lead down surprising and novel pathways(more on this following).

Rigorous Specification of Modelof Psychological Events

Rigorous specification of the historical model needsto be accompanied by even more rigorous specificationof a model of contemporary psychological events. Slop-py theories may skip breezily from descriptions of an-cient evolutionary environments to predictions aboutcontemporary variables. To be persuasive, a theoryneeds to specify the contemporary psychological pro-cesses that are assumed to have resulted from the an-cient operations of natural selection, and that in turnyield those predictions.

At minimum, it is necessary to specify the model ofcontemporary psychological events as distinct fromthe model of historical (evolutionary) events. Log-ically, the two models operate at different levels ofanalysis and specify relations between very differentclasses of variables. (Among other things, evolutionarymodels describe processes pertaining to populations,whereas psychological models describe questions per-taining to individuals.) Among audiences inexperi-enced in differentiating between these levels of analy-sis, the relatively unverifiable statements about ancientevolutionary processes may be lumped together withthe more immediately verifiable statements about con-temporary psychological processes. This may lead to afalse skepticism concerning the model of psychologi-cal processes. Clearer separation between the two lev-els of analysis increases the perceived verifiability ofthe model of contemporary psychological events.

If indeed the model of contemporary psychologi-cal events is perceived to have merit, then it is morelikely that the model of historical events will be per-ceived to have merit as well. The inferential distancefrom empirical observation to the acceptance of theevolutionary model is rarely spanned in a single leap;it is more readily traversed through the two more cau-tious logical steps identified in Figure 1. In fact, ac-ceptance of the more proximal model may often benecessary before psychological audiences are willingto consider acceptance of the evolutionary model.Thus, the articulation of a more coherent and com-

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plete psychological model will have the effect of in-creasing the perceived plausibility of that historicalmodel as well. Moreover, any increase in the treat-ment of the psychological model diminishes the rela-tive size of the historical model within the theoreticalwhole and thus decreases the relative proportion ofthe theory that is perceived to be unverifiable.

Explicit Articulationof Deductive Logic

Scientists often make deductive leaps intuitivelyand do not necessarily experience those leaps as exer-cises in logic. Consequently, a hypothesis that is de-duced from a set of preliminary assertions may be ex-pressed simply as an intuitively plausible predictionbut not as the end product of deductive reasoning.Within some theoretical contexts, this approach maywork just fine. However, within the context of evolu-tionary psychology—in which the inferential distancefrom initial assertion to hypothesis is perceptuallyhuge—this approach may be problematic. Evolution-ary psychological theories are more convincing if pre-sented within a narrative that clearly reveals the under-lying deductive logic.

There are several reasons for this. First, a coherentdeductive narrative reveals that an evolutionary theoryis truly a theory about psychological processes and isnot merely a post hoc explanation. This is a fundamen-tal distinction. Theories are “forward-thinking” enti-ties. They comprise sets of statements that are con-nected logically as the result of being deduced from thesame preliminary assertions. On the other hand, expla-nations are “backward-thinking” entities. They com-prise sets of statements that are connected psychologi-cally as a result of the attempt to explain the origins ofsome specific observed phenomenon. People intui-tively engage in both forward- and backward-thinkingprocesses. Individual scientists may seek theories forthe pragmatic purpose of finding explanations, andtherefore backward-thinking explanatory processesnaturally play a role in discoveries of forward-thinkingtheories. Nevertheless, the logic of a theory exists sep-arately from the means through which it was discov-ered and from the phenomena for which it provides anexplanation. That logical distinction is not always evi-dent in the manner in which a theory is articulated,however. If theorists do not present an explicit accountof the deductive logic that forms the guts of any goodtheory, others may (with good reason) be more likely toassume that the theory is simply a convenient back-ward-thinking explanation of a single phenomenon orset of phenomena. On the other hand, if theorists ex-plicitly lay out the deductive logic that underlies thetheory, others will be more likely to perceive the theoryas something that exists separate from a set of phenom-ena that they theory may (or may not) have originally

been developed to explain. This articulation of the de-ductive logic of a theory helps a theory to appear—andto be—more forward thinking.

Second, careful articulation of deductive logic en-hances the perceived explanatory coherence of a the-ory (Thagard, 1992). The perceived coherence of thetheory suffers whenever links between different ele-ments of the theory are unclear. Any slippage or mys-tery in the connection between the historical and con-temporary levels of analysis (symbolized by c in Fig-ure 1) undermines the persuasiveness of the historicalmodel. Any perceived looseness in the manner inwhich hypotheses are generated also maintains skepti-cism. Convincing evolutionary psychological theoriesrequire careful articulation of the deductive logicthrough which a model of psychological events is de-duced and through which hypotheses testing thismodel are generated.

Consider the following example. Suppose we startwith the intuitively appealing assumption that in an-cient environments it would have been adaptive if wehelped those genetically related to us (i.e., our kin) butless adaptive if we helped nonkin. Ignoring our ownadvice—for the sake of expediency—to engage in afull cost–benefit analysis, let’s say we loosely base thisassumption on the idea that, from a gene survival view-point, we potentially have a lot to gain by ensuring thatour kin survive and nothing directly to gain by ensuringthat our nonkin survive. In addition, suppose we de-duce from this assumption that, in contemporary times,we should help our kin more than our nonkin.

This sounds reasonable on the surface, but it’s slop-py. It leavesoutall the stepsbetween theancientpast andthepsychologicalpresent.Forexample, itdoesnotartic-ulate exactly what psychological processes would havebeen involved in the adaptation. This failure can havenegative consequences: The skeptic may reasonably ar-gue that people do not frequently think about genetic re-latedness in an explicit way, and the skeptic may dismissthe theory on these grounds. This sloppy deduction alsodoes not articulate how those psychological processesmight influence contemporary helping behavior. This,too, can have negative consequences: The skeptic maythink the theory suggests that people rarely or never helpnonkin and may readily produce many instances wherepeople do help those with no genetic relationship.Again, the skeptic may dismiss the theory—quite rea-sonably—on these grounds.

Articulating the deductive logic more explicitlymakes such easy outs more difficult to come by. For ex-ample, let’s start again with the assumption that help-ing kin, from an adaptationist perspective, is moreadaptive than helping nonkin. Therefore, one could ar-gue, it would have been adaptive to distinguish be-tween kin and nonkin in a quick and efficient waythrough the use of salient kinship cues. These cueswould trigger psychological responses (emotions, cog-

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nitions) that compel quick behavioral helping respons-es. In contemporary times, these psychological pro-cesses (sensitivity to kinship cues, linkage betweenperception of cues and emotion or cognition) remainand influence contemporary helping behavior when(and only when) those cues are present.

Articulating the preceding outlined steps makes itclearer what specific predictions the theory does anddoes not make. It thus does not allow the skeptic todismiss the theory on, say, the grounds that peopledon’t explicitly think very much about genetic relat-edness—because the newly articulated deductionmakes it clear that they are not expected to. As a re-sult, it is far more compelling than the original,sloppy version devoid of such specific linkages.Thus, it is to evolutionary psychologists’ advantage topresent as much of the deductive logic that attemptsto link ancient environments to contemporary pro-cesses as possible. As we have shown, the logical andpsychological gap between the two is enormous, andevolutionary psychologists do not have very muchroom with which to be sloppy.

Generation of Truly NovelPsychological Implications

Rigorous deductive logic not only strengthens the in-ternal coherence of a theory but also provides an impor-tant means of generating novel hypotheses. This is notonly essential to a progressive program of scientific re-search (Lakatos, 1970), it also is one of the primarymeans through which theories prove to be persuasive.Indeed, the generation of novel hypotheses has been thefocus of statements attesting to the merit of evolutionarypsychological theories (Buss et al., 1998), as well asstatements expressing concerns about their utility (Ca-porael & Brewer, 2000; Forster & Shapiro, 2000). Itseemsclear thatpeopleareunlikely tobeexcitedbyevo-lutionary psychological theories that appear merely toexplain previously observed phenomena or to offer al-ternative conceptual structures within which to locatepreviously articulated hypotheses. People will be morecompelled by evolutionary psychological theories thatyield novel hypotheses specifying previously undocu-mented psychological phenomena.

Of course, conceptual novelty is more a matter ofuniqueness than temporal precedence. Logically, itmatters not at all who first articulates a hypothesis if, infact, it turns out that the same hypothesis can also bededuced from alternative theoretical frameworks. Theevolutionary theories that are most likely to be persua-sive are those that yield hypotheses that cannot be de-duced from other theories and that remain uniquelydeducible over time. Hypotheses like these are rarely ar-rived at through intuitive means alone. This suggeststhat the greatest intellectual dividends offered by evolu-tionary psychology will follow from the adoption of an

inquisitive“let’s seewhere this takesus”approach:Startwithaplausibleassertionaboutsomesetofevolutionaryconstraints and consider the various consequences thatfollow logically from that assertion. In doing so, it isvaluable to ignore easy temptations to arrive at previ-ously discovered or intuitively obvious destinations andinstead to try to find routes to subtle, surprising, previ-ously unchartered psychological territory.

Conceptually novel hypotheses are rarely simple.Complex interaction effects involving three or morevariables are almost always less obvious than meremain effects of one variable on another. Also, the morecomplex the interaction, the less easy it is to identify al-ternative explanations for the effect (Conway, Schaller,Tweed, & Hallett, in press). Among the evolutionarypsychological theories that are most useful and con-vincing to skeptics are those that yield complex hy-pothesis specifying not only how people (and subsetsof people) think, but also the specific domains withinwhich those psychological processes do and do notproceed and the specific contexts that trigger those do-main-specific psychological processes. One exampleis provided by evolutionary psychological work on thedomain- and situation-specificity of human reasoningprocesses: On the basis of the assumption that, in an-cient environments, it would have been adaptive to de-tect social “cheaters” (that is, persons who violated im-plicit social contracts), it was deduced that personswould reason differently in cheater-detection situa-tions than in situations not relevant to social contractviolations. Tests of these proposed domain-specificreasoning abilities have supported this notion (e.g.,Cosmides, 1989; but see Pollard, 1990). Other evolu-tionary psychological theories yielding similarly com-plex hypotheses are emerging in the areas of socialcognition and interpersonal behavior (Gangestad &Simpson, 2000; Kurzban & Leary, 2001; Neuberg &Cottrell, in press; Schaller, in press). Within the con-temporary psychological environment, convincing testsof theories typically depend on the deduction of andempirical support for these sorts of complex and two-and three-way interactions. Thus, when attempting touncover and articulate theories in evolutionary psy-chology, it will become increasingly important to ar-ticulate theories that not only predict general humantendencies but also predict specific domains and situ-ational contexts that moderate (amplify or inhibit)those tendencies.

Forge Conceptual IntegrationsBetween Alternative Modelsof Psychological Events

Psychologically and logically, a theory is less per-suasive under conditions in which a different theoryyields the same hypotheses. There is a logical caveat tothis alternative explanations rule, however: To the de-

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gree that the alternative theoretical explanation is logi-cally compatible with the specified theory, this shouldlessen the negative impact of that alternative explana-tion on the perceived veracity of the theory. Indeed,psychological phenomena are almost always multiplydetermined, and it is rare that alternative explanationsidentify incompatible psychological processes. Thus,although legitimate alternative explanations will al-ways reduce the perceived veracity of a theory, at apurely logical level this ought to be moderated to somedegree by the logical compatibility of the theories un-der the microscope.

This point is especially relevant when consideringevolutionary psychological theories and the nonevo-lutionary processes that are often offered as alternativeexplanations for phenomena predicted by evolutionarytheories. Many of these alternative explanations spec-ify psychological processes that are logically inde-pendent of the processes specified by evolutionarypsychological models. For instance, evolutionary psy-chological theories concerning gender differences insexual behavior typically specify (or imply) the exis-tence of some contemporary physiological basis forobserved gender differences. Plausible alternative ex-planations typically focus on the existence of somecontemporary cultural norms as the basis for observedgender differences. Obviously, there is nothing incom-patible about the coexistence of physiological and cul-tural structures. Nor is the alternative explanation—theexistence of specific cultural norms—incompatiblewith any model of evolutionary events precipitated bythe constraints of differential parental investment. Infact, the existence of gender-relevant cultural normscan actually be deduced logically from the same evolu-tionary starting point (Schaller, 1997). This is not un-common. Many hypothesized evolutionary pressuresrelevant to psychology could logically have led simul-taneously to the emergence of specific physiologicalstructures and to the emergence of specific social struc-tures that reify or amplify or both the operation of thosephysiological structures (Boyd & Richerson, 1985;Dunbar, Knight, & Power, 1999; Durham, 1991; Janic-ki & Krebs, 1997; Lumsden & Wilson, 1981; Toma-sello, 1999; Tooby & Cosmides, 1992).

The implication for evolutionary psychological the-orists is this: By pursuing multiple deductive paths thatfollow from initial assertions, it is possible to articulateinternally coherent theories describing the historicalemergence and contemporary operation of differentsets of psychological processes. By linking multiplemodels of psychological processes to the same histori-cal origins, it is possible not only to decrease the num-ber of ostensible alternative explanations that bear neg-atively on the persuasiveness of an evolutionary theorybut to incorporate those explanations into the theory sothat they bear positively instead (see also Simpson &Gangestad, 2001). The result, if successful, will be a

theory that has greater explanatory coherence (Tha-gard, 1992) and so is all the more persuasive.

Attempts to do this not only serve evolutionary psy-chological theories, but also—by providing conceptualintegrations of superficially unrelated psychologicalprocesses—provide important benefits to the psycho-logical sciences in general.

Concluding Remarks

To be allowed to tread on the schoolyard of scientificdiscourse, a theory has to meet certain minimal criteriasuch as falsifiability. Once admitted through that gate,however, these minimal criteria matter very little to theultimate success of that theory. Survival on the harshplayground of scientific skepticism depends on manydeeper features that contribute to the theory’s utility, asjudged by scientists. Scientists judge a theory to be use-ful to the extent that they perceive it to be true. Scientistsare people, and people judge a theory to be true to the ex-tent that it is perceived to be verifiable. However impor-tant it ispsychologically, though,verifiabilitymaintainslittlepresence in thepositivistphilosophyofscience thatmost psychological scientists are taught to follow. It isnot surprising, therefore, that inferential doubts basedon verifiability are expressed instead in the culturallyacceptable language of falsifiability.

If these doubts are taken literally, they are easily dis-missed, and it is all too common for enthusiasts of evo-lutionary psychology to shrug off criticisms expressedin the language of falsifiability—to attribute these crit-icisms to ignorance or enmity or both. To do so, how-ever, is to miss an opportunity for critical reflection.Lurking within these misdirected criticisms is a sub-stantial truth: For reasons both logical and psychologi-cal, theories within evolutionary psychology are differ-ent from other sorts of theories in psychology. They arenot different in kind but in degree: the degree to whichthey are verifiable and thus the degree to which they areintuitively persuasive. The upshot is that evolutionarypsychological theories must be crafted more carefully,articulated more precisely, and tested more rigorouslyif they are to overcome the skepticism that naturallygreets them. Individual scientists have a responsibilityto these theories, as we all do to all youthful but prom-ising theoretical approaches within our field. When re-sponding negatively to evolutionary psychological the-ories, scientists have a responsibility to criticize themthoughtfully, to identify legitimate flaws. When re-sponding positively to evolutionary psychological the-ories, scientists have a responsibility to attend to thoseflaws as well, to improve on them. Through carefulintellectual parenting, these promising theories maysurvive long enough to contribute substantially andpersuasively to our understanding of contemporary hu-man psychological processes.

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References

Archer, J. (1996). Sex differences in social behavior: Are the socialrole and evolutionary explanations compatible? American Psy-chologist, 51, 909–917.

Arrow, H., & Burns, K. L. (in press). Self-organizing culture: Hownorms emerge in small groups. In M. Schaller & C. S. Crandall(Eds.), The psychological foundations of culture. Mahwah, NJ:Lawrence Erlbaum Associates, Inc.

Bechtel, W. (1988). Philosophy of science: An overview for cognitivescience. Hillsdale, NJ: Lawrence Erlbaum Associates, Inc.

Bem, D. J. (1972). Self-perception theory. In L. Berkowitz (Ed.),Advances in experimental social psychology (Vol. 6, pp. 1–62).New York: Academic.

Boyd, R., & Richerson, P. J. (1985). Culture and the evolutionaryprocess. Chicago: University of Chicago Press.

Buss, D. M. (1989). Sex differences in human mate preferences:Evolutionary hypotheses tested in 37 cultures. Behavioral andBrain Sciences, 12, 1–49.

Buss, D. M., Haselton, M. G., Shackelford, T. K., Bleske, A. L., &Wakefield, J. C. (1998). Adaptations, exaptations, and span-drels. American Psychologist, 53, 533–548.

Buss, D. M., & Schmidt, D. P. (1993). Sexual strategies theory: Anevolutionary perspective on human mating. Psychological Re-view, 100, 204–232.

Caporael, L. R., & Brewer, M. B. (1995). Hierarchical evolutionarytheory: There is an alternative, and it’s not creationism. Psycho-logical Inquiry, 6, 31–34.

Caporael, L. R., & Brewer, M. B. (2000). Metatheories, evolution,and psychology: Once more with feeling. Psychological In-quiry, 11, 23–26.

Conway, L. G., III. (1999). Noise, logic, and the span of time. Ameri-can Psychologist, 54, 440–441.

Conway, L. G., III, Schaller, M., Tweed, R. G., & Hallett, D. (2001).The complexity of thinking across cultures: Interactions be-tween culture and situational context. Social Cognition, 19,228–250.

Cosmides, L. (1989). The logic of social exchange: Has natural se-lection shaped how humans reason? Studies with the Wason se-lection task. Cognition, 31, 187–276.

Crandall, C. S., & Schaller, M. (in press). Scientists and science:How individuals’ values shape collective norms. In M. Schaller& C. S. Crandall (Eds.), The psychological foundations of cul-ture. Mahwah, NJ: Lawrence Erlbaum Associates, Inc.

Dawkins, R. (1976). The Selfish gene. New York: Oxford UniversityPress.

Dunbar, R., Knight, C., & Power, C. (1999). The evolution of culture.Edinburgh, Scotland: Edinburgh University Press.

Durham, W. H. (1991). Coevolution: Genes, culture, and human di-versity. Stanford, CA: Stanford University Press.

Eagly,A.H. (1987).Sexdifferences in socialbehavior:Asocial-role in-terpretation. Hillsdale, NJ: Lawrence Erlbaum Associates, Inc.

Eagly, A. H., & Wood, W. (1999). The origins of sex differences inhuman behavior: Evolved dispositions versus social roles.American Psychologist, 54, 408–423.

Festinger, L. (1957). A theory of cognitive dissonance. Evanston, IL:Row, Peterson.

Forster, M. R., & Shapiro, L . A. (2000). Prediction and accommoda-tion in evolutionary psychology. Psychological Inquiry, 11,31–33.

Gangestad, S. W., & Simpson, J. A. (2000). The evolution of humanmating: Trade-offs and strategic pluralism. Behavioral andBrain Sciences, 23, 573–644.

Garcia, J. (1981). Tilting and the windmills of academe. AmericanPsychologist, 36, 149–158.

Gigerenzer, G. (1998). Ecological intelligence: An adaptation forfrequencies. In D. D. Cummins & C. Allen (Eds.), The evolu-tion of mind (pp. 9–29). New York: Oxford University Press.

Gould, S. J. (1997, June 26). Evolution: The pleasures of pluralism.New York Review of Books, 44, 47–52.

Greenberg, J., Solomon, S., & Pyszczynski, T. (1997). Terror man-agement theory of self-esteem and cultural worldviews: Empir-ical assessments and conceptual refinements. Advances in Ex-perimental Social Psychology, 29, 61–139.

Greenwald, A. G., & Ronis, D. L. (1981). On the conceptual dis-confirmation of theories. Personality and Social PsychologyBulletin, 7, 131–137.

Higgins, E. T. (1992). Increasingly complex but less interesting arti-cles: Scientific progress or regulatory problem? Personality andSocial Psychology Bulletin, 18, 489–492.

Horgan, J. (1996). The end of science. New York: BroadwayBooks.

Hull, D. L. (1988). Science as a process. Chicago: University of Chi-cago Press.

Janicki, M. G., & Krebs, D. L. (1997). Evolutionary approaches toculture. In. C. Crawford & D. L. Krebs (Eds.), Handbook ofevolutionary psychology (pp. 163–207). Mahwah, NJ: Law-rence Erlbaum Associates, Inc.

Kelley, H. H. (1967). Attribution theory in social psychology. In D.Levine (Ed.), Nebraska Symposium on Motivation (Vol. 15, pp.192–238). Lincoln: University of Nebraska Press.

Kenrick, D. T., & Keefe, R. C. (1992). Age preferences in mates re-flect sex differences in mating strategies. Behavioral and BrainSciences, 15, 75–91.

Kenrick, D. T., & Simpson, J. A. (1997). Why social psychologyand evolutionary psychology need one another. In J. A.Simpson & D. T. Kenrick (Eds.), Evolutionary social psychol-ogy (pp. 1–20). Mahwah, NJ: Lawrence Erlbaum Associates,Inc.

Ketelaar, T., & Ellis, B. J. (2000). Are evolutionary explanationsunfalsifiable? Evolutionary psychology and the Lakatosian phi-losophy of science. Psychological Inquiry, 11, 1–21.

Kitcher, P. (1985). Vaulting ambition: Sociobiology and the quest forhuman nature. Cambridge, MA: MIT Press.

Kitcher, P. (1993). The advancement of science. New York: OxfordUniversity Press.

Kruglanski, A. W. (1994). The social-cognitive bases of scientificknowledge. In W. R. Shadish & S. Fuller (Eds.), The social psy-chology of science (pp. 197–213). New York: Guilford.

Kruglanski, A. W. (2001). That “vision thing”: The state of theory insocial and personality psychology at the edge of the new mil-lennium. Journal of Personality and Social Psychology, 80,871–875.

Kunda, Z., & Thagard, P. (1996). Forming impressions from stereo-types, traits, and behaviors: A parallel-constraint-satisfactiontheory. Psychological Review, 103, 284–308.

Kurzban, R., & Leary, M. R. (2001). Evolutionary origins of stigma-tization: The functions of social exclusion. Psychological Bul-letin, 127, 187–208.

Lakatos, I. (1970). Falsification and the methodology of scientific re-search programmes. In I. Lakatos & A. Musgrave (Eds.), Criti-cism and the growth of knowledge (pp. 91–196). Cambridge,England: Cambridge University Press.

Latané, B., & L’Herrou, T. (1996). Spatial clustering in the confor-mity game: Dynamic social impact in electronic groups. Jour-nal of Personality and Social Psychology, 70, 1218–1230.

Laudan, L. (1977). Progress and its problems. Berkeley, CA: Uni-versity of California Press.

Lewontin, R. C. (1990). The evolution of cognition. In D. N. Osher-son & E. E. Smith (Eds.), An invitation to cognitive science:Thinking (pp. 229–246). Cambridge, MA: MIT Press.

Lumsden, C. J., & Wilson, E. O. (1981). Genes, mind, and culture:The coevolutionary process. Cambridge, MA: Harvard Univer-sity Press.

Merton, R. K. (1942). Science and technology in a democratic order.Journal of Legal and Political Sociology, 1, 115–126.

165


Neuberg, S. L., & Cottrell, C. A. (in press). Intergroup emotions: Abiocultural approach. In D. M. Mackie & E. R. Smith (Eds.),From prejudice to intergroup relations: Differentiated reactionsto social groups. Philadelphia: Psychology Press.

Peters, R. H. (1976). Tautology in evolution and ecology. AmericanNaturalist, 110, 1–12.

Pollard, P. (1990). Natural selection for the selection task: Limits tosocial exchange theory. Cognition, 36, 195–204.

Popper, K. R. (1959). The logic of scientific discovery. New York:Hutchison Education.

Quine, W. (1953). From a logical point of view. Cambridge, MA:Harvard University Press.

Richardson, R. C. (1996). The prospects for an evolutionary psy-chology: Human language and human reasoning. Minds andMachines, 6, 541–547.

Richardson, R. C. (2000). Epicycles and explanations in evolution-ary psychology. Psychological Inquiry, 11, 46–49.

Schaller, M. (1997). Beyond “competing,” beyond “compatible.”American Psychologist, 52, 1379–1380.

Schaller, M. (in press). Ancestral environments and “motivated” so-cial perception: Goal-like blasts from the evolutionary past. InS. Spencer & S. Fein (Eds.), Motivated social cognition: TheNinth Ontario Symposium. Mahwah, NJ: Lawrence ErlbaumAssociates, Inc.

Schaller, M., & Conway, L. G., III. (1999). Influence of impres-sion-management goals on the emerging contents of group ste-reotypes: Support for a social-evolutionary process. Personalityand Social Psychology Bulletin, 25, 819–833.

Schaller, M., & Conway, L. G., III. (2000). The illusion of unfalsi-fiability and why it matters. Psychological Inquiry, 11, 49–52.

Schaller, M., & Crandall, C. S. (1998). On the purposes served bypsychological research and its critics. Theory and Psychology,8, 205–212.

Scher, S. J. (1999). Are adaptations necessarily genetic? AmericanPsychologist, 54, 436–437.

Schmidt, D. P., & Buss, D. M. (2001). Human mate poaching: Tac-tics and temptations for infiltrating existing mateships. Journalof Personality and Social Psychology, 80, 894–917.

Sherif,M.(1936).Thepsychologyofsocialnorms.NewYork:Harper.Simpson, J. A., & Gangestad, S. W. (2001). Evolution and rela-

tionships: A call for integration. Personal Relationships, 8,341–355.

Solomon, S., Greenberg, J., & Pyszczynski, T. (1991). A terror man-agement theory of social behavior: The psychological functionsof self-esteem and cultural worldviews. Advances in Experi-mental Social Psychology, 24, 93–159.

Thagard, P. (1992). Conceptual revolutions. Princeton, NJ: Prince-ton University Press.

Tomasello, M. (1999). The human adaptation for culture. Annual Re-view of Anthropology, 28, 509–529.

Tooby, J., & Cosmides, L. (1992). The psychological founda-tions of culture. In J. Barkow, L. Cosmides, & J. Tooby(Eds.), The adaptive mind: Evolutionary psychology andthe generation of culture (pp. 19–136). New York: OxfordUniversity Press.

Tooby, J., & DeVore, I. (1987). The reconstruction of hominid be-havioral evolution through strategic modeling. In W. G.Kinzey (Ed.), The evolution of human behavior: Primatemodels (pp. 183–237). Albany, NY: State University of NewYork Press.

Wallach, M. A., & Wallach, L. (1998). When experiments serve littlepurpose: Misguided research in mainstream psychology. The-ory and Psychology, 8, 183–194.

Wood, W., & Eagley, A. H. (2000). A call to recognize the bredth ofevolutionary perspectives: Sociocultural theories and evolu-tionary psychology. Psychological Inquiry, 11, 52–55.

Wrangham, R. W. (1987). The significance of African apes for re-constructing human social evolution. In W. G. Kinzey (Ed.),The evolution of human behavior: Primate models (pp. 51–71).Albany, NY: State University of New York Press.

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