526 Animal Behaviour, 43, 3

hypothesis of Alexander (1974) and the kin selec- tion or inclusive fitness hypothesis of Hamilton (1964). The latter theory, which was first formu- lated to explain the frequent shift from solitary to social forms of life among the Hymenoptera, but later on was generalized to cover all occurrences of sociality, explains why non-reproductive forms can maintain themselves over generations: they help relatives (who are carrying at least part of the gen- etic basis for being an efficient helper) achieve more offspring. Thereby their helper genome is perpetu- ated. The parental manipulation hypothesis (the helpers have no choice; environmental restraints imposed by the parents make helping the best option) stresses the plasticity of the genome which, in social species, allows for a number of well- adapted phenotypes. Various predictions that follow from the different theoretical approaches lead to overlapping results. Instead of the sudden appearance of a gene for 'altruism' (to my delight the word does not occur in this book!) an 'epi- genetic' basis for helping has been proposed (West Eberhard 1987). Just as the words concave and con- vex describe the two sides of a curved surface, and cooperation and competition are different scale dimensions of the same interactions, the parental manipulation hypothesis and the inclusive fitness model are complementary explanations. For social evolution to occur, the genetic basis of individuals should evolve to accommodate an increased pheno- typic plasticity. Whereas parental manipulation puts the main emphasis on the mechanisms that exploit this plasticity, kin selection describes the margins between which these mechanisms may wander without being removed by selection. Among these mechanisms competition is the major structuring force. This competition can be modu- lated into covert and ritualized forms, but cannot be replaced by de novo mechanisms. For instance, when laying workers occur in colonies of bumble- bees or honey bees, they do not possess the means to maximize their inclusive fitness. This implies that the degree of relatedness alone never led to sociality, but it always plays a role whenever sociality arises. There are numerous examples from early stages of sociality within the Hymenoptera and from cooperatively breeding birds (Stacey & Koenig 1990), and now also from the mole-rat, which show that helping is directed more to close kin.

However, because biologists wanted to translate kin selection into directly operating mechanisms, such as kin recognition, much confusion has arisen in the literature. Some of this confusion seems to be present in several sections of the present book. In my opinion, a book review is not the proper place to discuss this, nor does it make sense to illustrate my

point by citing isolated sentences. Not every argu- ment is convincing, particularly in the first chapter, and there is some demagogy (for instance, all brood care by Hymenoptera is called sub-social behav- iour, and by doing so the frequency of the step towards eusociality appears to become less signifi- cant; the very lucid terminology of Michener 1974, is thereby eroded). The important function of the book is that it stimulates our thinking. Its editors and its authors help its readers to mature their ideas, and by doing so they certainly obtain a pay-off.

H. H. W. VELTHUIS Department o f Ethology and Socio-ecology, Laboratory of Comparative Physiology, University of Utrecht, 3508 TB Utrecht, The Netherlands.

References

Alexander, R. D. 1974. The evolution of social behavior. A. Rev. Ecol. Syst., 5, 325-383.

Hamilton, W. D. 1964. The genetical evolution of social behaviour. I, If. J. theor. Biol., 7, 1-52.

Michener, C. D. 1974. The Social Behavior of the Bees. Cambridge, Massachusetts: Belknap Press of Harvard University Press.

Stacey, P. B. & Koenig, W. D. Eds. 1990. Cooperative Breeding in Birds. Cambridge: Cambridge University Press.

West Eberhard, M. J. 1987. The epigenetical origins of insect sociality. In: Chemistry and Biology of Social Insects (Ed. by J. Eder & H. Rembold), pp. 369-372. Miinchen: Peperney Verlag.

Biology and Cognitive Development: the Case of Face Recognition. By MARK H. JOHNSON & JOHN MORTON. Oxford: Blackwell (1991). Pp. x + 180. Price s hardback, s paperback.

Much of this book is devoted to the exposition of a theory of how young animals come to recognize conspecifics. The theory proposes that the young of many vertebrate species possess two distinct mech- anisms which function to produce this ability. One, called 'conspec', provides a representation of the general characteristics of conspecifics, and ensures that a young animal's or infant's attention and behaviour are directed towards them. This represen- tation does not require any experience of other indi- viduals for its development. The other mechanism, 'conlern', builds up representations of familiar individuals, enabling them to be recognized.

The authors build the case for the theory on behavioural and neurophysiological evidence, including many of their own findings obtained from human infants and from chicks. In doing so, they give a thorough and meticulous treatment of

Book Reviews 527

experimental methods and results from a range of disciplines, taking the reader carefully through all the details needed to make their case. The result is a firmly grounded theory which succeeds in explain- ing subtle and complex findings from imprinting and infant face recognition, and which can make a wealth of testable predictions. This is scientific theory-building of the highest quality, and is essen- tial reading for all ethologists and psychologists interested in the development of social behaviour.

The authors' aims go beyond exposition of the theory, as the book is in part also a more general essay on the relationship between psychology and biology. Their arguments for the importance of ethology and physiology in understanding human cognitive development deserve close attention from psychologists, but there is much of importance for ethologists as well. There is an excellent review of the remarkable research of Johnson, Horn and their colleagues, which revealed the existence of'conspec' and 'conlern' in chicks, and which has advanced our understanding of imprinting enormously. One fascinating historical irony in their conclusions is the easy acceptance that the 'conlern' mechanism is neurally distinct from other associative learning processes; a suggestion which would have been highly contentious, though impossible to test adequately, 30 years ago.

The book also has implications for the study of behavioural development which go beyond the confines of imprinting. The authors have a pro- ductive stab at the 'innateness' issue, and propose a distinction between the species-typical and the individual-specific environments, which they use to define the concept of a 'primal' behavioural mech- anism. This definition succeeds in capturing what we mean when we want to use the word 'innate', while keeping it clearly fenced off from notions of genetic programming. Finally, although the authors do not say so explicitly, the book can be read as a powerful manifesto, solidly backed by experimental evidence, for the study of behavioural development as a problem in its own right. Differ- ences in developmental pathways can certainly be explained in terms of natural selection, but the basic dynamics of development are too intricate to be packaged and labelled as adaptive 'enabling mechanisms' serving genetic programmes. The out- standing research and theory described by Johnson and Morton represent a major step on our way to understanding these dynamics.

Department of Psychology, University of Nottingham, Nottingham NG7 2RD, U.K.

PATRICK GREEN