Morphological preview effects in English are restricted to suffixed words

Kelly M. Dann, Aaron Veldre, & Sally Andrews

The University of Sydney, School of Psychology

Short title: Morphology in the parafovea

Contact details

Kelly M. Dann

School of Psychology, The University of Sydney

Sydney, NSW 2006

Australia

kelly.dann@sydney.edu.au

© 2021, American Psychological Association. This paper is not the copy of record and may not exactly replicate the final, authoritative version of the article. Please do not copy or cite without authors' permission. The final article will be available, upon publication, via its DOI: 10.1037/xlm0001029

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Abstract

Much of the evidence for morphological decomposition accounts of complex word

identification has relied on the masked-priming paradigm. However, morphologically

complex words are typically encountered in sentence contexts and processing begins before a

word is fixated, when it is in the parafovea. To evaluate whether the single word-

identification data generalize to natural reading, Experiment 1 investigated the contribution of

morphological structure to the very earliest stages of lexical processing indexed by preview

effects during sentence reading in the gaze-contingent boundary paradigm. Preview

conditions systematically assessed the impact of prefixed and suffixed nonword previews that

manipulated stem and affix overlap, and affix status, against an orthographically legal control

baseline. Initial fixations on suffixed target words showed a preview benefit from nonwords

that combined the target stem with a legitimate affix, but not with a non-affix, while prefixed

targets only benefited from an identical preview. When presented in a masked prime lexical

decision task in Experiment 2, the same stimuli yielded equivalent stem priming from

suffixed and prefixed primes regardless of affix status, consistent with previous masked

priming studies using similar nonword primes. The early effects of morphological structure

selectively observed on parafoveal processing of suffixed words are inconsistent with recent

non-morphological, position-invariant accounts of embedded stem activation. These results

provide the first evidence of morphological parafoveal processing in English and contribute

to recent evidence that readers extract a higher level of information from the parafovea during

natural reading than was previously assumed.

Keywords

Reading, eye movements, morphology, parafoveal processing, masked priming.

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Morphemes are the smallest meaning-bearing units in language, e.g., a complex word

such as unbreakable can be decomposed into three component morphemes: the prefix un, the

stem break, and the suffix able. A central question in language research concerns the role that

these component morphemes play in lexical retrieval of morphologically complex words.

Most theories of morphological processing assume that component morphemes contribute to

identification of complex words but, despite decades of research, questions about precisely

how and when they are extracted and the relative contribution of orthographic and semantic

information to morphological decomposition remain a source of ongoing debate. Theories of

morphological processing of written words have relied principally on evidence from isolated

word identification tasks and priming paradigms (see Amenta & Crepaldi, 2012;

Diependaele, Grainger, & Sandra, 2012, for reviews). However, in normal reading, complex

words are typically encountered in sentence contexts. The central goal of the present research

is to evaluate whether the morphological effects observed in priming tasks generalize to more

naturalistic sentence reading contexts. Before elaborating the rationale for the eye movement

methods we apply to address this issue, we briefly overview recent debates about

morphological processing.

Decomposition or direct stem activation?

The influential full decomposition account of multimorphemic word recognition (Taft

& Foster, 1975) assumes that the stem morpheme of a complex word (e.g., break) functions

as the ‘access code’ to a cluster of morphologically structured representations. Early models

assumed an initial prelexical parsing process that stripped affixes from the complex word to

isolate the stem required for the access process (Taft, 2004; Taft & Forster, 1975). More

recent extensions of the decomposition account adopt an interactive activation framework in

which form-level representations corresponding to both free stem morphemes, and bound

morphemes, such as affixes, mediate access to whole word representations (e.g., Crepaldi,

Rastle, Coltheart & Nickels, 2010; Diependaele, Sandra & Grainger, 2009) or lemma units

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(Taft, 2015). In both accounts, morphological segmentation is based solely on orthographic

form, and independent of semantic influences, and therefore referred to as morpho-

orthographic decomposition (Rastle, Davis, & New, 2004).

The strongest evidence for morpho-orthographic decomposition comes from masked

priming lexical decision experiments which show equivalent priming between genuinely

morphologically-related derived word primes and their stems (e.g., hunter – HUNT) as that

observed for pseudo-derived pairs (a real stem + a real affix but without a genuine

morphological relationship e.g., corner – CORN), under conditions in which priming does not

occur for word pairs that have the same degree of orthographic overlap, such as turnip –

TURN, but where ip is not a real affix (e.g., Rastle et al., 2004). This evidence that masked

priming depends on the morphological status of the affix has been widely replicated (see

Rastle & Davis, 2008 for a review) and confirmed by more recent research (e.g.,

Beyersmann, Ziegler et al., 2016) that tightly controlled semantic and morphological factors

claimed to confound interpretation of some of the evidence for morpho-orthographic

decomposition (e.g., Baayen, Milin, Durdevic, Hendrix, & Marelli, 2011). Converging

evidence for the morpho-orthographic account also derives from other methodologies

including masked transposed-letter priming (Beyersmann, Castles, & Coltheart, 2011;

Beyersmann, Duñabeitia, Carreiras, Coltheart, & Castles, 2013) and event-related potentials

(Beyersmann, Iakimova, Ziegler, & Cole, 2014).

The generality of this signature of morphological decomposition has been challenged

by recent evidence that masked priming from nonword primes is insensitive to the

morphological status of the affix. Morris, Porter, Grainger, and Holcomb (2011) reported

equivalent priming from genuinely-derived word primes (flexible- FLEX), pseudo-derived

non-word primes (flexify-FLEX) and non-affixed non-word primes (flexint– FLEX) (see also

Milin, Feldman, Ramscar, Hendrix, & Baayen, 2017). Parallel evidence of equivalent

priming of French words by pseudo-derived and non-affixed non-words (Beyersmann,

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Casalis, Ziegler, & Grainger, 2015; Beyersmann, Cavalli, Casalis & Cole, 2016) led to the

conclusion that the stem morpheme in a complex word is activated without explicit prior

decomposition.

To account for these data, Grainger and Beyersmann (2017) proposed an edge-aligned

embedded word activation account of morphological decomposition which assumes that

lexical access occurs through direct activation of the stem embedded in a complex word,

without requiring pre-lexical processing to decompose and isolate the stem. Instead, the

whole-word representation of an embedded stem is directly activated by a complex word in

the same way as it would be for the simple form, as long as the embedded word is aligned

with the beginning or end of the word. The absence of an adjacent letter is assumed to

enhance the visual salience of the embedded word and support automatic activation of the

whole-word representation of the stem. To reconcile the lack of effect of affix status for

nonword previews with the previous results obtained with word primes (e.g., stronger

priming for corner – CORN than turnip - TURN), Grainger and Beyersmann (2017) argued

that the whole word-representation of the word prime (e.g., corner, turnip) yields inhibition

that can be counteracted by the presence of a genuine affix in the segmented letter-string

which ‘boosts’ activation of the stem.

Thus, in contrast to full decomposition models, the embedded word activation account

assumes that the initial segmentation of complex words is “a strictly non-morphological

process” (p. 289) that relies on representations of whole-word forms rather than specialized

morphological representations or affix-stripping mechanisms. However, like full

decomposition approaches, it assumes that skilled readers extract stems via an automatic

“semantically ‘blind’ morpho-orthographic parsing mechanism” (Grainger & Beyersmann,

2017, p. 308) which is assumed to develop at higher levels of reading proficiency through

reading experience and exposure to morphologically complex words which enables

orthographic representations to be established for both whole word forms and affixes (e.g.,

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Beyersmann, Grainger et al., 2015; Hasenacker et al., 2016). The validity of pure

orthographic accounts of morphological decomposition has been challenged by evidence that

masked priming can be influenced by the semantic transparency of the relationship between

the prime and target (e.g., Feldman, O’Connor, & Moscoso del Prado Martin, 2009; Jared,

Jouralev, & Joanisse, 2017). Morphemes lie at the intersection between orthography and

semantics, so early effects of morphological structure are consistent with a range of

theoretical accounts that argue for the “simultaneous engagement of all sources of

information – formal or meaning-related – in the task of identifying a word in print”

(Schmidtke, Matsuki, & Kuperman, 2017, p. 1810), and challenge the claim that morpho-

orthographic decomposition is ‘semantically blind’.

The present research was not designed to directly assess the relative contribution of

orthographic and semantic processing to decomposition, although it may contribute evidence

relevant to that issue. However, the central goal was to evaluate the generality and timecourse

of morphological decomposition effects – whatever their source – by investigating whether

they generalize beyond the masked priming tasks that have dominated the literature on

morphological processing to eye-movement indices during sentence reading. To provide

novel evidence about the nature and timecourse of decomposition, we investigated whether it

influences the earliest stages of lexical processing, which begin when the word is in the

parafovea - before it is directly fixated. In this context, the critical evidence for a

morphological decomposition process is that it is restricted to stimuli that are ‘exhaustively

decomposable’ into morphemic units (Milin et al., 2017). That is, morphological

decomposition of complex nonwords will be specific to stimuli that combine a word stem

with a genuine affix.

Prefixed vs. suffixed words

Further insight into the decomposition process is provided by a comparison of

prefixed and suffixed words. Both the full decomposition and the edge-aligned embedded

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word activation accounts assign priority to the stem due to its status as a lexical unit

independent of its functional role in a complex word. In the decomposition accounts, affixes

are parsed pre-lexically to reveal the stem access code; in the edge-aligned account the stem

is directly activated, and any ‘boost’ to activation due to morphological structure of the letter

string occurs post-lexically. Both accounts therefore imply that the processing of prefixed and

suffixed words should not differ.

However, there are a number of functional differences between prefixes and suffixes

that may influence how they are processed. Suffixed words include both inflected and derived

forms which can change the stem both semantically and syntactically, while prefixes are

typically derived forms, so change the meaning of the word only. Orthographically, suffixes

can also change the form of a stem (e.g. dropping the e in composing), while prefixes

preserve the entire stem. Differences in the time-course of processing may also arise due to

the left-to-right parsing that is assumed in many models of English word identification (e.g.,

Coltheart, Rastle, Perry, Langdon & Ziegler, 2001; Davis, 2010). The basic orthographic

syllabic structure (BOSS) model predicts the stem access code will be extracted earlier in a

suffixed word such as payment, than in a prefixed word such as prepay (Taft, 1979). On the

other hand, the affix of a prefixed word is available earlier for affix-stripping. Furthermore,

during reading of connected text, the distance between the point of fixation and the stem/affix

of an upcoming word will differ for prefixed versus suffixed words, which may influence

when morphological information becomes available.

Relatively few studies have directly compared prefixed and suffixed forms. Early

work in French by Cole, Beauvillain, and Segui (1989) found that lexical decision latencies

for suffixed words displayed stem frequency effects, consistent with morphological

decomposition and lexical access via the stem morpheme, while prefixed words showed

surface frequency effects, consistent with whole-word processing. They concluded that

morphological decomposition is not obligatory, and that differences may be due to the

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interaction between the sequential organization of prefixes and suffixes, and left-to-right

parsing. For suffixed words the stem is available first, so rapid on-line processing is best

achieved by access via the stem, but the stem of a prefixed word can only be determined once

the prefix is identified, and therefore lexical access often proceeds via the whole-word form.

In contrast to this conclusion, Feldman and Larabee (2001) reported that lexical decision

responses to suffixed targets (e.g., payment) showed equivalent facilitation from prefixed and

suffixed morphological relatives (e.g., prepay vs payable) in both short lag (250 ms) and long

lag (average of 10 items) visual priming paradigms suggesting that the benefit of a shared

stem morpheme did not depend on the relative order of the stem and affix.

This conclusion is supported by recent research that used the masked priming

paradigm to directly compare processing of prefixed and suffixed forms. Beyersmann,

Cavalli et al. (2016) found equivalent priming of French target words by genuinely prefixed

and suffixed non-word primes (preamour – AMOUR, amouresse – AMOUR) and non-affixed

primes (brosamour – AMOUR, amourugne – AMOUR) relative to an unrelated control

condition. Similar findings for prefixed and suffixed words in English were recently reported

by Heathcote et al. (2018): both genuinely-affixed (subcheap – CHEAP, cheapize - CHEAP)

and non-affixed (blacheap – CHEAP, cheapstry - CHEAP) nonword primes yielded

significantly greater priming than an unrelated condition (miscall – CHEAP, idealism -

CHEAP). Heathcote et al. (2018) interpreted the results as supporting Grainger and

Beyersmann’s (2017) claim that position-invariant embedded word activation is independent

of morphological structure. However, in contrast to Beyersmann, Cavalli, et al. (2016),

Heathcote et al. (2018) observed a graded pattern of priming: the affixed condition yielded

significantly more priming than the non-affixed condition. This was attributed to the use of

‘interpretable’ affixes (e.g., subcheap, cheapize) which may facilitate post-lexical “attempts

to ‘re-combine’ stem and affix … to compute a meaning for the novel input string” (p. 8) and

boost activation of the embedded stem. However, they acknowledged that the graded priming

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effects were also compatible with evidence of early semantic influences on decomposition

(e.g., Feldman et al., 2009; Jared et al., 2017), raising questions about whether the activation

of embedded word stems is the “strictly non-morphological process” proposed by Grainger

and Beyersmann (2017, p. 289).

Using eye movements to assess morphological processing

The single word identification and masked priming tasks that have provided the

majority of evidence about morphological processing provide limited insight into normal

reading, where complex words are typically encountered in sentence contexts. Studies of eye

movements during natural sentence reading provide greater ecological validity. They also

yield more direct evidence about the time course of morphological effects. Eye-movement

studies have demonstrated that lexical processing begins before a word is directly fixated -

when it is in the parafoveal area of vision. The influence of parafoveal processing in normal

sentence reading is typically assessed using the gaze-contingent boundary paradigm (Rayner,

1975), which allows for experimental manipulation of previews which are only available for

processing in the parafovea. When the reader’s eyes cross an invisible boundary to the left of

the target word, the preview is replaced by the correct form of the target word. Readers

therefore always fixate the correct target word, and are typically unaware of the display

change from the preview to the target because it occurs during a saccade. Nevertheless,

fixations on the target word are shorter when it replaces a valid or related preview than a

different, invalid preview, a phenomenon known as the parafoveal preview effect (see

Schotter, Angele, & Rayner, 2012; Vasilev & Angele, 2017, for reviews). The boundary

paradigm can therefore be used to investigate manipulations of preview-target similarity like

those investigated in single word masked priming tasks.

Until recently, parafoveal preview effects in English were thought to be limited to

processing of low-level orthographic (e.g., Inhoff & Tousman, 1990) and phonological (e.g.,

Pollatsek, Lesch, Morris, & Rayner, 1992) information, and it was assumed that higher-level

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information was not processed parafoveally. However, recent studies have demonstrated that

semantic and syntactic attributes of previews are processed in the parafovea (Schotter & Jia,

2016; Veldre & Andrews, 2016, 2017, 2018a, 2018b, 2018c; Veldre, Reichle, Wong, &

Andrews, 2020; see Andrews & Veldre, 2019, for a review). These findings renew interest in

the question of whether higher-level morphological information may also be extracted from

the parafovea.

Despite a large body of eye-movement evidence on the processing of compound

words (e.g., Andrews, Miller, & Rayner, 2004; Bertram & Hyönä, 2003; Hyönä & Pollatsek,

1998; Juhasz, 2008), relatively few studies have used eye movements to assess reading of

other morphologically-complex words. Beauvillain (1996) reported differences in the

timecourse of processing prefixed and suffixed French words that paralleled Cole et al.’s

(1989) lexical decision data: Suffixed words displayed stem frequency effects early in the

eye-movement record, suggesting that lexical access proceeds via the stem, but prefixed

words showed a later effect that only emerged on refixations, suggesting that lexical access

relied on the whole-word form.

More recent research in German has used the fast-priming paradigm (Sereno &

Rayner, 1992) to extend the results of single-word studies to sentence reading using eye-

movement recording. This procedure presents a brief prime after readers fixate on the target

location, which is then replaced with the target word. In contrast to the boundary paradigm,

the display change occurs in a fixated location so readers are consciously aware of it.

Consistent with the single-word masked-priming results for nonword primes (Beyersmann,

Cavalli et al., 2016), Mousikou and Schroeder (2019) found equivalent priming from

genuinely-affixed and non-affixed nonword primes, and no differences between prefixed and

suffixed forms. These results provide convergent evidence for the edge-aligned account

(Grainger & Beyersmann, 2017) in a more ecologically valid task. However, like masked

priming, fast priming only assesses early processing of a fixated target word. During normal

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sentence reading initial processing starts before a word is fixated. To investigate whether

morphological decomposition affects the earliest stages of lexical retrieval therefore requires

assessment of parafoveal processing.

Morphological processing in the parafovea. Evidence of parafoveal processing of

morphological information has been found cross-linguistically. In Hebrew, derived-form

previews which share the same root as the target have been found to yield a benefit on early

measures (first fixation and gaze duration) compared to an orthographic control (Deutsch,

Frost, Pelleg, Pollatsek, & Rayner, 2003; Deutsch, Frost, Pollatsek, & Rayner, 2005). In

Russian, inflected-form previews which share the same root as the target produced a preview

cost on early measures compared to an identical preview (Stoops & Christianson, 2017,

2019). Similarly, Korean previews with an incorrect morphosyntactic case-marker yielded a

preview cost (Kim, Radach, & Vorstius, 2012). In addition to preview effects, morphological

structure has also been shown to influence saccade-targeting. Although the initial landing

position is typically near the center of a word (i.e., preferred viewing location; Rayner, 1979),

studies in Uighur (Yan et al., 2014) and in Finnish (Hyönä, Yan, & Vainio, 2018) have

demonstrated an effect of morphological complexity: controlling for word length and launch

site, initial landing positions were closer to the beginning of words that contained more

affixes. Similar effect on landing position were observed in a recent comparison of parafoveal

preview effects in suffixed and monomorphemic Finnish words (Hyönä, Heikkilä, Vanio, &

Kliegl, 2021) but the study did not include a manipulation of the legality of the invalid affix

previews to determine whether parafoveal morphological influences were enhanced for

exhaustively decomposable nonword previews.

The only studies of morphological preview effects in English that we are aware of

failed to find evidence of parafoveal morphological processing of prefixed words (Kambe,

2004; Lima, 1987) or compound words (Juhasz, White, Liversedge, & Rayner, 2008). This

may indicate that such effects are limited to morphologically-rich languages like Hebrew,

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Finnish and Russian. However, no studies to date in English have investigated suffixed

forms. Further, both Kambe (2004) and Lima (1987) assessed preview effects of

morphologically related nonwords that replaced either the affix or the stem with random

consonants (e.g., rehsxc or zvduce as a preview for reduce) relative to baselines of X-mask

placeholders (e.g., xxxxxx) and illegal consonant-strings (cwxyjq). Orthographically atypical

parafoveal previews have been demonstrated to attract attention parafoveally, yielding both

parafoveal-on-foveal disruption (Rayner, 1975; Schotter et al., 2012) and high preview costs

(e.g., Hutzler et al., 2013; Veldre & Andrews, 2018b). Assessing preview effects against

orthographically illegal baselines, and including illegal strings in the morphologically related

conditions, may have reduced sensitivity to Kambe’s and Lima’s morphological

manipulations.

The current study

The aim of the current research is to contribute novel evidence to the debate about

pre-lexical decomposition by investigating morphological influences on word identification

during sentence reading. Experiment 1 assessed the contribution of morphological structure

to the very earliest stages of lexical processing in on-line sentence reading indexed by

parafoveal preview effects in the boundary paradigm. The experiment improved upon past

studies using the gaze-contingent boundary paradigm to investigate morphological processing

in English (Kambe, 2004; Lima, 1987) by directly comparing prefixed and suffixed words.

Paralleling recent masked priming studies (Beyersmann, Cavalli et al., 2016; Heathcote et al.,

2018), the preview conditions assessed the impact of morphologically structured nonwords

against an orthographically legal control baseline. As illustrated by the example in Figure 1,

the five preview conditions systematically varied the degree of morphological overlap with

prefixed and suffixed targets by comparing reading times on the same target word when

preceded by nonword previews that were: (1) identical to target, (2) same stem + different

genuine affix, (3) same stem + non-affix, (4) different stem + same affix, and (5) different

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stem + different affix (control). Greater preview benefit for the genuinely-affixed condition

than the non-affixed condition would support theories that assume early, exhaustive

morphological decomposition. However, evidence of equivalent preview benefits for same-

stem conditions regardless of affix type, and no benefit for a preview that only shared an affix

with the target, would be more compatible with theories that attribute morphological effects

to the lexical activation of the embedded stem.

(Insert Figure 1 here)

Both theoretical frameworks assume that similar morphological processes are applied

to prefixed and suffixed words in single word tasks in which stimuli are centrally fixated.

However, differences may arise in parafoveal processing due to either visual acuity or left-to-

right parsing mechanisms. The stems of suffixed words are closer to the fovea than those of

prefixed words, and processed earlier in the left-to-right sequence, so may therefore be more

likely to be extracted when the word is in the parafovea. Alternatively, if morphological

decomposition depends on some form of pre-lexical ‘affix-stripping’, the greater proximity of

prefixes in parafoveal words might yield stronger early morphological influences for prefixed

than suffixed targets.

To evaluate whether any morphological effects observed in the eye movement data

for Experiment 1 were due to idiosyncratic characteristics of our stimulus materials, we

conducted a masked prime lexical decision task (Experiment 2) using the stimuli from

Experiment 1 to allow direct comparison with the nonword priming effects that underpin

Grainger and Beyersmann’s (2017) edge-aligned account of morphological priming.

Experiment 1

Method

Participants. Fifty-two undergraduate students (Mage = 19.25, SD = 2.08, 61.5%

female) from The University of Sydney completed the experiment for partial course credit.

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All participants reported normal or corrected-to-normal vision, and that English was either

the first language they learned to read and write, or that it had been learned prior to age 5.

The study was approved by The University of Sydney Human Research Ethics Committee,

and participants provided written consent prior to participating in the study.

Materials and Design. One-hundred prefixed and 100 suffixed target words were

selected from the English Lexicon Project (ELP) database (Balota et al., 2007). All target

words were bimorphemic; i.e. comprised of a stem and one affix, and between 6 and 10

letters long. All targets were derived forms which contained a whole embedded stem,

unchanged by derivation (e.g., education would not meet criteria as educate is not embedded

in its whole form) to allow assessment of embedded-stem priming effects. To ensure all

target words were easily identifiable, only those with mean lexical decision accuracy greater

than 90% in the ELP database were selected. Prefixed and suffixed word lists were matched

as closely as possible on important psycholinguistic variables that may influence word

recognition (see Table 1).

(Insert Table 1 here)

There was no significant difference in ELP lexical decision accuracy for whole-word

(t = 1.86, p = .065) or stem forms (t = 1.12, p = .263), or in log SUBTLEX frequency

(Brysbaert & New, 2009) for whole word forms (t = -1.29, p = .199). However, stem

frequency was higher for prefixed words (t = 3.44, p = .001). Word length was matched for

stems (t < 1), however due to the prefixes for words higher than 90% in ELP accuracy being

shorter than suffixes, suffixed targets were slightly longer (t = -5.13, p < .001). To control for

the differences in the stem frequency and target length of prefixed and suffixed words, both

variables were included as covariates in the analyses. See Supplementary Materials for the

complete list of stimuli.

Previews in the gaze-contingent boundary paradigm must be of the same length as the

target, as a change in length is a salient cue that increases awareness of the display change.

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Non-word previews requiring different stems and different affixes were therefore created

from stems and affixes of the same length as the target words and of approximately

equivalent frequency. Non-word stem-affix combinations were always legal combinations of

letters i.e., they exist in genuine words. Non-word previews requiring non-affixes were

constructed from the non-affixes used by Heathcote et al. (2018) supplemented by a further

three two-letter non-affixes. It was not possible to match the variety of affixes in the suffixed

target words (25) and the prefixed target words (13). The productivity of the two sets of

affixes, as indexed by morphological family size (Rubin, 1978) was also significantly lower

for the set of suffixes than prefixes (355 vs 647; t = 5.66, p <.001). These differences reflect

the distribution of affixes in the SUBTLEX database and, more generally, in the corpus.

Additional analyses including affix length and productivity as covariates were conducted to

control for these differences.

Target words were embedded in neutral sentence frames of 7-14 words long (Mprefix =

10.48, Msuffix = 10.41, see Supplementary Materials). The target word was always embedded

more than two words from the beginning, but less than two words from the end of the

sentence, and was preceded by a pre-target word that was at least four letters in length. The

sentences were constructed to ensure that the target word was not predictable from the

preceding sentence context (see below). Five counterbalanced lists were created in which

each of the 200 sentences only occurred once, but across lists each sentence appeared in all

preview conditions.

Stimulus validation. The predictability of the target word in the sentences was

assessed in a separate norming study. A group of 21 students from The University of Sydney

who did not participate in the main experiment provided cloze norming data. Participants

were presented with all 200 sentences up to, and including, the pre-target word, and asked to

provide one word that they thought was most likely to come next in the sentence. Results of

the cloze task showed that the mean cloze probability for the target word was extremely low

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(M = 0.30%; range: 0-14%) and was similar for the prefixed and suffixed conditions (Mprefix =

0.48%; Msuffix = 0.19%). In addition to assessing whole-word predictability, the cloze

responses were also coded for stem and affix predictability, which were both also close to

zero: Mstem= 1.33% (prefixed: 1.62%; suffixed: 1.05%); Maffix=0.20% (prefixed: 0.43%;

suffixed: 0%). Thus, the target words, stems, and affixes were all very low in contextual

predictability.

Apparatus. Eye movements were recorded using a SR Research Eyelink 1000 Plus

with a sampling rate of 2000 Hz. Subjects read sentences displayed on a 21-in. View Sonic

CRT monitor with a refresh rate of 140 Hz. Sentences were displayed as a single line of text

in black monospaced Consolas font on a grey background. Participants were seated 60 cm

from the monitor, at which distance 2.5 characters subtended 10 of visual angle. Head

movements were minimized with a chin and forehead rest. Viewing was binocular, but only

the right eye was recorded.

Procedure. Participants were instructed to read the sentences silently for meaning,

and to answer occasional comprehension questions by pressing a key on a standard keyboard.

The experiment began with three practice trials to familiarize participants with the procedure.

This was followed by the individually randomized presentation of the 200 experimental

sentences, combined with 108 filler sentences.1 Following approximately 33% of sentences, a

two-alternative yes/no comprehension question requiring moderate understanding was

presented. The frequency of questions was matched between the prefixed and suffixed items.

At the beginning of the experiment, and before each block of approximately 60 sentences,

participants’ eye movements were calibrated using a 3-point calibration procedure. Maximum

calibration error accepted was 0.30 of visual angle. At the beginning of each trial, a circular

black fixation point appeared on the screen at the location of the first letter of the sentence as

1 Filler sentences comprised the stimuli of an unrelated experiment, of which 67% contained a display change.

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a gaze trigger. Participants were instructed to fixate on this point, and once their fixation was

stable, the sentence was displayed. If a stable fixation could not be made, or if calibration

error was above 0.3 degrees of visual angle, a new calibration was performed. After the

experiment, participants were asked if they had noticed anything unusual during the

experiment. If participants reported seeing a display change, they were asked to provide

details of what they had seen, and an estimate of how many times they noticed it. The entire

session was completed within 60 minutes.

Results

Data Preparation. Prior to analysis, fixations below 80 ms within one letter space of

an adjacent fixation were merged with that fixation and remaining individual fixations below

80 ms or above 1000 ms were excluded (4.93% of total fixations). Trials were excluded from

analysis if the participant blinked immediately before or after fixating the target word (5.13%

of trials). Trials were also excluded due to late display changes (occurring more than 10 ms

into a fixation); and early display changes, which occur when participants make a “j-hook”

saccade across the boundary before ultimately fixating to the left of the boundary (13.5% of

trials). Fixation duration outliers were also excluded if they exceeded 1000 ms for gaze

duration (< 1% of trials). After these exclusions, 8502 trials (81.75% of the data) were

available for analysis.

After excluding three participants with comprehension scores more than 2.5 standard

deviations below the mean, average comprehension accuracy for the remaining participants

was 94% (SD = 3.26; range 87% – 99%) indicating participants were reading for meaning.

The majority of participants were not aware of the display change manipulation; however,

three participants were excluded due to reporting seeing the display change more than 15

times.2 Therefore, the data from 46 participants was included in the analyses.

2 A further three participants reported seeing the display change more than 15 times but only noticed previews

that were illegal letter strings, which occurred only in the filler sentences. Their data were therefore retained.

17

Reading Measures. Three reading measures were analyzed: first fixation duration

(FFD) on the target word during first-pass reading, regardless of the number of fixations the

word received; single fixation duration (SFD), the duration of the first fixation on the target

word when only one first-pass fixation was made; and gaze duration (GD), the sum of first-

pass fixation durations on the target word. The means for each measure across preview

conditions for prefixed and suffixed target words are presented in Table 2.

(Insert Table 2 here)

The data were analyzed by (generalized) linear mixed-effects models (LMM) using

the lme4 package (Version 1.1-21; Bates, Mächler, Bolker, & Walker, 2015) in R (Version

3.5.3; R Core Team, 2019). Affix type (prefix versus suffix) was coded as an effect contrast.

The models included the fixed effects of stem frequency and target length as mean-centered

covariates3, and subject and item random intercepts, subject random slopes for the effects of

affix type and preview type, and item random slopes for the effects of preview type. Models

with more complex random-effects structures failed to converge. To control for the impact of

testing multiple dependent measures on the Type 1 error rate (von der Malsburg & Angele,

2017), the Bonferroni correction of dividing the .05 alpha threshold by three - the number of

dependent measures – was applied yielding alpha of 0.0125 (critical t/z value = 2.49). Effects

that reached the conventional .05 criterion used in previous studies of morphological

processing are noted as marginal. With two qualifications noted below, parallel analyses

performed on log-transformed duration measures yielded the same pattern of significant

results to the analyses of raw measures below.

Two analyses were conducted that used different sets of contrasts to assess the effects

of preview type nested under levels of affix type (i.e., prefixed targets and suffixed targets).

3 Additional models that also included affix productivity and affix length as covariates yielded an identical

pattern of effects of morphology.

18

The preview effect contrasts compared each related preview to the unrelated control condition

to assess the overall preview benefit from each morphologically related condition relative to

an unrelated, but orthographically legal baseline which has served as the index of

morphological priming in many masked priming studies (e.g., Beyersmann et al., 2016). The

successive differences contrasts assessed whether morphological structure yielded graded

preview effects by assessing the relative contribution of different morphological units to

parafoveal preview benefit.

Preview effect contrasts. There were no significant main effects of affix type on any

measure (all |t|s>1.51)4.

For suffixed targets, there was a significant identical preview effect on all measures

(all |t|s>3.05) because the target word was read more quickly when the preview was identical

to the target compared to an unrelated preview. For prefixed targets, this effect was

significant on both FFD (b=-18.60, SE=5.21, t=-3.57) and SFD (b=-18.85, SE=6.66, t=-2.83),

and marginally significant on GD (b=-17.29, SE=7.04, t=-2.46).5

Suffixed targets also showed a stem preview effect because readers benefited from a

preview sharing the same stem as the target word paired with a different suffix. This effect

was significant on FFD (b=-16.32, SE=4.70, t=-3.47), SFD (b=-22.89, SE=6.00, t=-3.82), and

marginally significant on GD (b=-16.85, SE=6.82, t=-2.47).6 The stem preview effect was not

significant on any measures for prefixed targets (all |t|s<1.62).

4 The models including affix length and productivity as covariates revealed a significant affix effect on gaze

duration (b=--16.48, SE=5.85, t=-2.82), and a marginally significant effect on first fixation (b=-7.486, SE=3.57,

t=-2.10), both reflecting longer fixations on suffixed than prefixed words. 5 The identical preview effect for prefixed targets was significant in the analysis of log-transformed gaze

duration (b=-0.06, SE=0.02, t=-3.00). 6 The stem preview effect for suffixed targets was significant in the analysis of log-transformed gaze duration

(b=-0.06, SE=0.02, t=-3.10).

19

The only indication of a preview benefit from stems paired with a non-affix was a

marginally significant effect on gaze duration for suffixed targets (b=--14.37, SE=6.83, t=-

2.10). This comparison was not significant on FFD or SFD measures for suffixed words

(|t|s<1.42), or on any measure for prefixed targets (|t|s<1.48).

There was no benefit from a preview that shared a prefix or suffix with the target

relative to an unrelated control preview on any measure (Prefixed targets: ts<1; Suffixed

targets: |t|s<1.74), i.e., there was no affix preview effect.

Successive differences contrasts. For prefixed targets, there was a significant

difference between the identical preview and the same stem + different affix preview on FFD

and SFD (ts>2.95), but not GD (t<1). However, suffixed targets showed this effect only on

GD (b=19.18, SE=6.61, t=2.90), but not on FFD or SFD (|t|s<1.16). The late emergence of an

identical preview benefit on gaze duration for suffixed words was due to refixations: Readers

were more likely to refixate suffixed targets following a same stem + different affix preview

versus an identical preview (b=0.46, SE=0.12, z=3.65). This comparison was not significant

for prefixed targets (z<1).

For suffixed targets, the same stem + different affix versus same stem + non-affix

contrast was marginally significant on FFD (b=9.75, SE=4.40, t=2.21), and significant on

SFD (b=15.53, SE=5.48, t=2.84), but not GD (t<1). The affix versus non-affix contrast was

not significant for prefixed targets on any measure (all ts<1).

The same stem + non-affix preview did not differ from the same affix + different stem

preview on any measure (Prefixed targets: all ts<1; Suffixed targets: all ts<1). The final

contrast in this set duplicated the non-significant affix priming contrast from the preview

effect comparisons (Prefixed targets: ts<1; Suffixed targets: |t|s<1.79).

In summary, the analyses of both overall preview effects and the graded effects

assessed by the successive differences contrasts revealed different patterns for prefixed and

suffixed targets. Suffixed words showed significant benefits on first-pass fixations from

20

previews that paired stems with a genuine affix relative to both unrelated previews and stems

paired with a non-affix that did not occur for prefixed words. In contrast, prefixed words

showed an early benefit from identical previews relative to same stem + different affix

previews that were not evident for suffixed words.

Supplementary analyses. To determine whether these findings were modulated by

oculomotor factors, supplementary analyses were conducted to assess effects of launch

distance and landing position.

Saccade launch distance. Morphological preview effects might be modulated by

visual acuity. Given the relatively long target words, readers’ perceptual spans may only have

included the entire preview stimulus when their previous fixation was close to the boundary.

Furthermore, the observed differences in preview effects for prefixed versus suffixed targets

might reflect the fact that the stem of a prefixed word lies further into the parafovea thereby

making it more difficult to process. Stem preview effects for prefixed words might therefore

only be observed in cases where the pre-boundary fixation is closer to the target word (Kliegl

et al., 2013). To account for this possible source of variance, the distance between the target

and the launch site of the saccade that crossed the boundary was included in LMMs as a

mean-centered, continuous predictor, along with interactions between launch distance and the

preview effects contrasts nested under levels of affix type.

The results of these analyses produced a virtually identical pattern of significant

effects as described in the main analyses.7 In addition, there were significant effects of launch

distance on all measures. On FFD and SFD, fixation durations were shorter following long

incoming saccades (Prefixed targets: both |t|s>4.99; Suffixed targets: both |t|s>2.60). In

contrast, gaze durations were longer following long incoming saccades, and this effect was

7 The only difference was that the overall stem preview effect for suffixed targets on gaze duration, which was

marginally significant in the main analysis of raw gaze duration, was significant in the analysis controlling for

launch distance (b=-17.17, SE=6.81, t=-2.52).

21

significant for suffixed targets (Prefixed targets: b=1.34, SE=0.75, t=1.79; Suffixed targets:

b=2.97, SE=0.82, t=3.61). The change in the direction of the effect between measures

suggests that, after a long incoming saccade, readers were likely to make a short fixation that

was terminated by a corrective refixation to move the eyes to a more optimal viewing

location for word recognition. Such corrections reduced the length of initial fixations, but

extended gaze duration. This interpretation was supported by a significant effect of launch

distance on first-pass refixation probability (Prefixed targets: b=0.13, SE=0.01, z=9.11;

Suffixed targets: b=0.13, SE=0.02, z=8.22).

There were also significant interactions between launch distance and the identical

preview effect on all measures (Prefixed targets: all |t|s>2.75; Suffixed targets: all |t|s>2.51)

because the preview effect was larger at closer saccade launch distances. This finding is

consistent with evidence that visual acuity modulates preview effects (Kliegl et al., 2013).

However, launch distance did not significantly modulate any of the other preview effects

(Prefixed targets: all |t|s<1.35; Suffixed targets: all |t|s<2.01). Thus, there was no evidence

that the absence of stem preview effects for prefixed targets depended on launch distance.

Initial landing position. As reviewed in the introduction, investigations of the

morphologically rich languages of Uighur (Yan et al., 2014) and Finnish (Hyönä et al., 2018,

2021) have suggested that parafoveal identification of a suffix may cause readers to adjust

their saccade targeting to land their eyes closer to the beginning of the word, to process the

stem, than the typical preferred viewing location slightly to the left of the word’s center

(Rayner, 1979). To test whether similar adjustments were evident in the present data, we

conducted an analysis of landing position on the target word with the preview effect contrasts

nested under the fixed effect of affix type, and mean-centered continuous predictors of launch

distance, stem frequency, and target word length.

Initial landing position was significantly closer to the word beginning following long

incoming saccades (b=-0.38, SE=0.01, t=-53.95), and significantly further into the word for

22

long targets (b=0.17, SE=0.03, t=5.61). However, there was no effect of affix type (t<1), and

no effects of preview type on landing position (Prefixed targets: all ts<1; Suffixed targets: all

ts<1). Thus, there was no evidence that readers used morphological information in the

parafovea to guide where they directed their saccades. Such effects may therefore be

restricted to morphologically rich languages (Hyönä et al., 2018, 2021; Yan et al., 2014).

These results also provide no evidence that the different patterns of preview effects for

prefixed versus suffixed targets were due to systematic differences in initial landing position.

Discussion

The present study provides the first evidence of morphological influences on

parafoveal processing in English, but showed that the early effects of morphological structure

indexed by parafoveal preview effects were limited to suffixed words. Prefixed words

showed a preview benefit from an identical preview, but no effects of stem overlap even at

close launch sites. In contrast, suffixed words showed as much benefit on first fixation and

single-fixation duration from a same stem + different affix preview as from an identical valid

preview, suggesting parafoveal extraction of the stem.8 However, in contrast with masked

priming results for single words assessing similar conditions, the stem preview benefit was

restricted to previews containing genuine affixes, and did not extend to stems paired with a

non-affix.

Experiment 2

To evaluate whether this evidence of morphological decomposition of suffixed words

was specific to parafoveal preview effects, the same materials were presented in a masked

8 In response to a reviewer’s query, we tested whether the different identity preview effects for prefixed and

suffixed words might be due to differences in position-specific bigram frequency at the affix boundary. These

comparisons showed that the difference between identical previews and same stem+different affix previews was

significant for suffixed conditions (p<.001) but not for prefixed words (p>0.2) and therefore cannot explain why

the identity preview effect was significant for prefixed but not suffixed words; while the difference between the

bigram frequency for same stem+non-affix and unrelated previews was significant for prefixed previews (p<.01)

but not for suffixed previews (p>0.5) so cannot explain why only suffixed words showed any evidence of a

preview benefit for non-affix previews.

23

prime lexical decision experiment to establish whether they replicated the findings of recent

studies of morphological processing using prefixed and suffixed nonword primes

(Beyersmann, Cavalli et al., 2016; Heathcote et al., 2017; Mouiskou & Schroeder, 2019).

Consistent with the methods used in these studies, the target stimuli were word stems and

matched nonwords.

Method

Participants. Fifty undergraduate students (Mage=20.82, SD=4.81, 64% female) from

The University of Sydney completed the experiment for partial course credit. All participants

began to learn to read and write English by at least age 5 and none had completed Experiment

1. The study was approved by The University of Sydney Human Research Ethics Committee,

and participants provided written consent prior to participating in the study.

Materials and Design. The same non-word previews used for the affixed, non-

affixed and unrelated conditions of Experiment 1 were used as the primes in Experiment 2.

Consistent with the majority of masked prime lexical decision experiments, the targets in

Experiment 2 were the stems of the complex word targets used in Experiment 1. Target stems

corresponded to 90 prefixed and 90 suffixed target words from Experiment 1.9 In addition to

these 180 word targets, 180 non-word targets were selected from a list of legal non-words

included in the English Lexicon Project (ELP) database (Balota et al., 2007). The non-words

differed from the target stems by 2-3 letters (e.g. PURE - NIRE) with a range of letter

substitution positions. Prefixed and suffixed targets were matched as closely as possible on

important psycholinguistic variables. Word length was matched (Prefixed: M=5.24, Suffixed:

M= 5.31, t <1) but, in the reduced list, ELP lexical decision accuracy was slightly higher for

prefixed stems than suffixed stems (0.97 vs. 0.95; t = -2.07, p = .02), and, as in Experiment 1,

9 The total number of target stems used in Experiment 2 was reduced from the 100 prefixed and 100 suffixed

complex target words used in Experiment 1 due to removal of cases where two complex words were derived

from the same stem. Because the targets were always stems and primes were always affixed, there was no

parallel to the Identical and same-affix conditions of Experiment 1.

24

log SUBTLEX frequency was higher for prefixed stems than suffixed stems (M= 3.30 vs 2.88

t = -3.36, p <.001). To control for the differences in stem frequency of prefixed and suffixed

words, it was included as a covariate in the analysis10.

Target words were primed by the affixed, non-affixed and unrelated non-word

previews from Experiment 1. Primes for the non-word targets were created to match the word

conditions by modifying the affixed and non-affixed primes for a given word target (e.g.

enpure, napure for PURE) to create the prime for the corresponding non-word (e.g. ennire,

nanire for NIRE). As in Experiment 1, the unrelated prime for a given target stem

corresponded to the non-word created for a different target. The experiment therefore

comprised a total of 360 trials consisting of 180 target words paired with 90 prefixed and 90

suffixed non-word primes (30 x 3 prime types), and 180 target non-words paired with 90

prefixed and 90 suffixed non-word primes. Prefixed and suffixed prime trials were

intermixed and presented in an individually, quasi-randomized sequence that minimized long

sequences of items from the same condition. Three counterbalanced lists were created to

ensure that participants only saw each target once and that, across participants, all targets

were paired with each of the three prime types. Stimuli are included in Supplementary

Materials.

Procedure. Participants completed the experiment individually or in small groups of

up to three in a quiet, darkened room. Stimuli presentation and recording of data was

controlled by DMDX software (Forster & Forster, 2003). Participants were instructed that

their task on each trial was to decide if the string of uppercase letters presented was a real or a

nonsense word, as quickly and accurately as possible. Responses were made by pressing the

left or right shift keys on the keyboard. The experiment began with 18 practice trials to

familiarize participants with the procedure. Each trial began with the 500 ms presentation of a

10 Additional models including affix length and productivity yielded identical outcomes.

25

forward mask of 14 hash marks followed by the prime in lowercase letters for 50 ms, and

then the target in uppercase letters for 3000 ms, or until the participant responded. After the

experiment, participants were debriefed and asked if they had noticed anything unusual

during the experiment. If participants reported any awareness of the prime, they were asked

to provide details of what they had seen.

Results

The majority of participants did not report awareness of the prime, and those who did

were not able to provide any identifying features of the prime stimulus. Therefore, the data

from all 50 participants was included in the analyses. Prior to analysis, latencies below 200ms

(3 trials) or above 1500ms (18 trials) and trials that timed out (21 trials) were removed. For

the RT analysis, incorrect responses (4.54% of the data) were removed. Mean reaction times

and error rates across prime conditions for prefixed and suffixed target words are presented in

Table 3.

(Insert Table 3 here)

The RT data and error data were analyzed by LMM and GLMM, respectively. Affix

type (prefix versus suffix) was coded as an effect contrast. The effect of prime type was

assessed by two planned contrasts nested under levels of affix type: (1) Stem priming effect:

the average of the related primes vs. the unrelated prime, and (2) Morphological priming

effect: affixed vs. non-affixed primes. To control for differences in stem frequency between

the prefixed and suffixed targets, the models included the fixed effect of stem frequency as a

mean-centered covariate. Models included subject and item random intercepts, and by-subject

and by-item random slopes for priming contrasts. Models with more complex random-effects

structures failed to converge. A parallel analysis of log-transformed RT yielded an identical

pattern of results to the analysis of raw RT reported below.

The RT analysis revealed significant stem priming reflecting faster responses to

26

targets primed by related than unrelated primes (Prefixed: b=12.65, SE=4.93, t=2.57;

Suffixed: b=24.37, SE=4.94, t=4.93). However, there was no difference in the size of the

priming effect between the affixed and non-affixed conditions (Prefixed: t<1; Suffixed:

b=8.62, SE=6.02, t=1.43). The main effect of affix type was not significant (t<1).

The analysis of error rates yielded a similar pattern of results as the RT analysis. The

overall error rate was low, but significantly more errors were made in the unrelated prime

condition than in the related conditions for prefixed targets (b=0.60, SE=0.20, z=3.07) but not

suffixed targets (b=0.29, SE=0.15, z=1.88). There were no differences in error rates between

the affixed and non-affixed conditions for either prefixed or suffixed targets (both zs<1). The

main effect of affix type was not significant (b=-0.25, SE=0.21, z=-1.19).

Discussion

Experiment 2 demonstrated that the stimuli used in Experiment 1 replicated the two

critical features of the pattern of masked priming reported in recent studies using

morphologically complex nonword primes. First, consistent with the findings of Beyersmann,

Cavalli et al. (2016) and Mousikou and Schroeder (2019) in French and German,

respectively, we found equivalent masked priming of word stems by affixed and non-affixed

nonword primes. In contrast with Heathcote et al.’s (2019) study of English, the data did not

show enhanced priming for nonword primes constructed from genuine affixes, consistent

with their suggestion that this boost in priming may be limited to stimuli explicitly

constructed to be semantically interpretable.

Second, consistent with all three studies, the pattern of priming did not differ between

prefixed and suffixed primes. The masked priming manipulations differed from those used to

assess preview effects in Experiment 1 because the target words in Experiment 1 were all

affixed words. This was essential to equate the length of the previews and targets, which is

necessary to limit participants’ awareness of display changes in the boundary paradigm. Stem

morphemes were used targets in Experiment 2 because this is the procedure adopted in

27

Beyersmann, Cavalli et al. (2016) and Heathcote et al.’s (2019) studies. Mousikou and

Schroeder (2019) found identical patterns of masked priming for stem and affixed targets,

and for blocked and mixed presentation of prefixed and suffixed words suggesting that such

procedural variations have little impact on masked priming effects.

Thus, when tested under the conditions of the masked priming task in which the

complex nonwords were directly fixated, our stimulus materials showed the pattern of

priming predicted by the embedded word activation account (Grainger & Beyersmann, 2017).

This suggests that the discrepancies from this pattern observed in Experiment 1 are specific to

parafoveal preview effects during sentence reading rather than arising from idiosyncrasies of

our stimulus materials.

General Discussion

Traditional full decomposition accounts of complex word identification have been

challenged by recent findings of significant and equivalent masked priming by genuinely-

affixed and non-affixed non-word primes for both prefixed and suffixed forms (Beyersmann,

Cavalli, et al., 2016, Heathcote et al., 2018). These results have been interpreted as evidence

that lexical access for morphologically complex words proceeds via direct activation of the

embedded stem, without pre-lexical decomposition. The present research investigated

whether these findings generalize to online sentence reading by assessing morphological

influences on parafoveal processing using the gaze-contingent boundary paradigm. Recent

evidence that parafoveal preview effects are sensitive to semantic and contextual plausibility

(see Andrews & Veldre, 2019, for review) show that substantial lexical processing often

occurs for parafoveal words, before they are directly fixated. If stems are accessed during the

early stages of lexical retrieval, they should yield parafoveal preview effects on early eye

movement measures paralleling the effects observed in single word masked priming tasks.

The eye movement data of Experiment 1 showed that stems were activated during

parafoveal processing. However, they also demonstrated two critical caveats on these effects

28

that have important theoretical implications. First, early stem preview effects on parafoveal

processing were restricted to suffixed words. Second, the effects observed for suffixed words

appeared to reflect morphological structure rather than activation of embedded stems. The

evidence for these conclusions is summarized below.

Overall preview effects assessed against an orthographically legal unrelated nonword

baseline provide the most direct comparison with the masked priming effects assessed in

single word paradigms (e.g., Beyersmann, Cavalli, et al., 2016; Heathcote et al., 2018), and

avoid the problems associated with the illegal baselines used in Kambe (2004) and Lima’s

(1987) studies of parafoveal morphological processing. For both prefixed and suffixed

targets, these comparisons revealed that both early and late fixation measures were

significantly shorter when the target was preceded by a valid identical preview than when the

preview was an unrelated nonword. These effects replicate the standard benefit of parafoveal

preview observed in the boundary paradigm (Schotter et al., 2012).

However, the major finding of Experiment 1 was that morphological influences on

parafoveal preview effects were restricted to suffixed words, particularly for early measures.

The stem preview effect only occurred for suffixed words; prefixed targets showed no

evidence of a benefit from previews that comprised the same stem paired with a different

affix. The differential stem preview effect for prefixed and suffixed words on early fixations

was confirmed by the graded effects revealed by the successive differences contrasts.

Prefixed words showed a significant benefit for identical over same stem + different affix

previews on first fixation duration and single fixation duration but suffixed words showed as

much benefit from previews of the target stem with a different affix as from identical

previews. Critically, suffixed words also showed a significantly stronger preview effect on

single fixation duration when the same stem was paired with a different, legitimate affix

29

rather than a non-affix (e.g. dietion vs. dietnel as previews for dietary). 11 There was no

parallel benefit for a preview in which the target stem was paired with a non-affix relative to

either an unrelated preview or a preview combining a different stem with the target affix. The

data therefore indicate that parafoveal preview effects for suffixed words on initial fixations

were limited to exhaustively decomposable morphologically structured nonword previews.

Thus, the results provide evidence that parafoveal processing is sensitive to

morphological structure, but only for suffixed words. These findings appear to be

incompatible with Grainger and Beyersmann’s (2017) claim that activation of edge-aligned

embedded stems is morphologically blind, and occurs for both prefixed and suffixed words.

Previous studies that assessed parafoveal morphological processing in English using

the boundary paradigm tested only prefixed words and detected no sensitivity to

morphological structure (Kambe, 2004; Lima, 1987). The current results are therefore

consistent with the null findings for prefixed words, but do not support the conclusion that

morphological information is not extracted from the parafovea. The results of Experiment 1

suggest that morphological structure does influence word identification during sentence

reading in English, but only for suffixed words. The data therefore add to recent evidence of

relatively deep parafoveal processing during reading (see Andrews & Veldre, 2019).

These findings contrast with the results obtained for the same stimuli in the single

word masked priming task used in Experiment 2, which replicated the evidence of equivalent

priming from affixed and non-affixed primes for both prefixed and suffixed forms found in

previous masked priming studies using nonword primes (Beyersmann, Cavalli et al., 2016;

Mousikou & Schroeder, 2019). The results of Experiment 1 also differ from Mousikou and

Schroeder’s (2019) fast-priming eye-movement data in German, which showed equivalent,

11 The effect on FFD was significant by the conventional .05 criterion but failed to exceed the Bonferroni-

adjustment recommended by von der Marlsburg and Angele (2017).

30

significant priming by genuinely-affixed and non-affixed non-word primes across both

prefixed and suffixed forms.

The critical difference between the gaze-contingent boundary paradigm used in

Experiment 1 and Mousikou and Schroeder’s eye tracking task is that the fast priming

procedure presented the affixed nonword prime after participants fixated on the location of

the target word, which was occupied by a mask consisting of unrelated prior to its fixation.

Thus, no parafoveal preview of the affixed nonword prime was available, and it was

presented foveally, at the point of readers’ fixation, as it is in the masked priming task. In

contrast, in the boundary paradigm the preview can only be processed parafoveally – it is

replaced with the target word during the saccade before the reader fixates that location. The

boundary paradigm therefore provides unique insight into parafoveal processing of

morphological information that is not tapped by the fast priming task. The fact that Mousikou

and Schroeder’s fast priming results duplicated the findings of masked priming studies

suggests that position-invariant activation of embedded stems may be specific to conditions

in which a brief prime stimulus appears in the same foveal location as the target. Norris and

Kinoshita’s (2008, 2012) Bayesian Reader model proposes that such conditions “trick the

perceptual system into processing primes and targets as a single perceptual object” (p. 450)

and tap generalized mechanisms involved in recovering information from noisy visual input

rather than indexing activation of specialized linguistic representations of morphemic or

lexical constituents shared by the prime and target. Stem morphemes are typically longer and

more salient than affix units so their letters may be more likely to be successfully recovered

from the noisy composite visual input. Consistent with the possibility that morphologically-

blind stem activation effects are specific to spatiotemporal conditions in which the prime and

target are treated as a single object, effects of morphological structure and semantic

transparency typically emerge with prime durations above approximately 60 ms (e.g., Rastle,

Davis, Marslen-Wilson & Tyler, 2000), which allow perceptual segregation of the prime and

31

target.

Under the more natural reading conditions of the boundary paradigm, where lexical

processing can be initiated before a word is fixated, the results of Experiment 1 suggest that

lexical retrieval mechanisms are sensitive to the morphological structure of suffixed forms in

the parafovea, and do not simply reflect activation of the stem morpheme. However,

consistent with Kambe’s (2004) and Lima’s (1987) findings, parafoveal preview effects did

not occur for prefixed words. There are two possible explanations of the absence of

parafoveal morphological decomposition of prefixed words.

First, it may reflect the constraints of visual acuity: embedded stems of prefixed forms

fall further into the parafoveal region, where visual acuity is reduced. This may limit the

depth of parafoveal processing, and account for the absence of stem preview effects for

prefixed words. However, contradicting this possibility, the results revealed significant

effects of parafoveal manipulations of affix legality for suffixed previews, even though these

units fell further from fixation than the onset of the stems of prefixed words, i.e., in regions

where visual acuity is low. Further evidence against the contribution of visual acuity to the

differences between prefixed and suffixed words is provided by the supplementary analyses

of launch distance and landing position. As expected, launch distance had robust effects on

general sensitivity to parafoveal information reflected in larger identical preview effects at

close launch sites (Kliegl et al., 2013). However, there was no evidence that it modulated the

differences between morphologically-related previews, or that it depended on affix type.

Similarly, there was no evidence of the morphological complexity effect on initial landing

position observed in Uighur (Yan et al., 2014) and Finnish (Hyönä et al., 2018, 2021)

indicating that the parafoveal effects of morphological structure detected in Experiment 1

were not due to systematic differences in initial landing positions on prefixed versus suffixed

words. In combination, then, the present results suggest that visual acuity alone is unlikely to

explain the lack of stem preview effects for prefixed words.

32

There is a second, essentially opposite explanation of how visual acuity might account

for the lack of morphological preview effects for prefixed words. In same-stem + different

affix previews of prefixed targets, the changed component (i.e., the prefix) forms the initial

letters of the preview (e.g., inforest/abforest as previews for deforest). The salience and

proximity of these initial letters in the highest acuity parafoveal region may increase the

disruptive effects of the discrepancy between the preview and the target and lead to a preview

cost that outweighs any benefit from morphological similarity between them. This

interpretation is consistent with a large body of eye-movement evidence showing that word-

initial letters facilitate parafoveal processing during reading (e.g., Briihl & Inhoff, 1995;

Inhoff, 1989; White, Johnson, Liversedge, & Rayner, 2008). The disruptive effects of

changing the initial letters may explain why prefixed targets showed a preview effect for

identical relative to same-stem previews on initial fixation duration (e.g., deforest vs. inforest)

that was not evident for suffixed targets. There were no other significant preview effects for

prefixed words, perhaps because stem preview benefits were counteracted by interference

from the different initial letters. The present study was not designed to distinguish between

‘affix-stripping’ (e.g., Taft & Forster, 1975, 1976) and interactive activation accounts of

morpho-orthographic decomposition (e.g., Taft, 2015). However, the fact that greater

parafoveal availability of prefix units appeared to hinder rather than help early morphological

decomposition seems incompatible with a process that depends on pre-lexical affix-stripping.

Early identification and stripping of the prefix should enhance extraction of the stem, even

when the target contains a different affix. The precise predictions of interactive accounts of

morphographic decomposition are more difficult to specify because they depend on the

relative frequency of the form units for stems and affixes.

In contrast to the results for prefixed targets, the results for suffixed words are

consistent with a process that depends on the preview being exhaustively decomposable into

morphemic units. This implies that morphological structure contributed to the preview effect

33

and that it was not simply due to orthographic overlap between the preview and target, which

was equivalent for the genuinely affixed and non-affixed conditions. The selective stem

preview effect observed for suffixed words may arise because the ‘edge-aligned’ stem of

such words falls in the highest acuity in the parafoveal region, potentially facilitating its early

activation. Grainger and Beyersmann’s (2017) account attributes any additional preview

benefit due to the legitimacy of the affix to the ‘secondary role’ of a genuine affix to ‘boost’

stem activation. The ‘secondary role’ is not well-defined in the edge-aligned account, but

Crepaldi, Hemsworth, Davis, and Rastle (2016) suggested that lexical representations for

different types of morphemic units may have different properties. For example, stems appear

to have position-invariant coding, so that the same stem can be accessed in both prefixed and

suffixed forms, while affixes occur in fixed positions, and therefore rely on position-specific

orthographic codes. Evidence that a shared affix alone is sufficient to yield masked priming

effects for both prefixed (Chateau, Knudsen, & Jared, 2002) and suffixed (Crepaldi et al.,

2016) words led Crepaldi et al. (2016) to propose that affixes may play a more active role in

complex word recognition. However, the absence of significant preview effects for the same

affix + different stem conditions for either prefixed or suffixed words in Experiment 1

suggests that affixes are not automatically extracted from the parafovea. Most critically, the

preview effects on the duration of initial fixations on suffixed words depended on the

legitimacy of the suffix in parafoveal vision. Such early influences of affix status, even for

low acuity regions, appear to be inconsistent with the late, secondary role of morphological

structure proposed by Grainger and Beyersmann (2017).

The present evidence of parafoveal effects of morphological structure on eye

movement measures for suffixed words converges with Schmidtke et al.’s (2017) recent

application of survival analysis (Reingold & Sheridan, 2014) to determine the earliest point at

which a range of orthographic, semantic and morphological variables influenced first fixation

duration during sentence reading. Across three sets of eye-movement data they found a very

34

early influence of the whole word frequency of derived suffixed words that was

contemporaneous with, or even preceded, the effect of the frequency of the word’s stem,

suggesting that morphemes and whole words are processed in parallel. This timecourse was

argued to be incompatible with pure orthographic accounts, in which decomposition into

morphemes is a prerequisite for access to complex word forms, but consistent with a range of

models that “allow for even partial orthographic information to activate meanings of complex

words and their morphemes in a parallel rather than sequential way” (Schmidtke et al., 2017,

p. 1810). Although Schmidtke et al.’s analyses did not directly tap parafoveal processing,

they noted that a number of form-related variables exerted an earlier influence on fixation

time than observed in a parallel analysis of single word lexical decision latencies, consistent

with effects of parafoveal preview, and suggested that further research should explore

whether contextual predictability facilitates early extraction of semantic information from

parafoveal words. Such processes may contribute to the very early effects of morphological

structure observed for suffixed words in Experiment 1.

Conclusion

To our knowledge, the current research provides the first evidence of parafoveal

processing of morphological information during reading in English. The results also highlight

the importance of collecting converging data from multiple paradigms to assess the impact

and timecourse of psycholinguistic manipulations on natural reading (see also Feldman, Dale,

& van Rij, 2019). The present findings suggest that morphological structure influences the

processing of complex words in the parafovea, but only for suffixed forms. These findings

complement recent evidence that readers extract high-level lexical information from the

parafovea (see Andrews & Veldre, 2019). Since lexical retrieval processes appear to begin in

the parafovea, early effects of morphological decomposition in reading may be most clearly

detected in measures based on information extracted prior to fixation.

35

Author Note

We thank Curtis Chan for his assistance with data collection. This research was

supported under Australian Research Council's Discovery Projects funding scheme (project

numbers DP160103224 and DP190100719). The data, analysis script, and stimulus materials

from this study are available at osf.io/sf89p

36

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46

Table 1

Mean word length (letters), log frequency, and lexical decision task accuracy of target words

Characteristic Target word Stem

Prefixed Suffixed Prefixed Suffixed

Length 7.69 (1.32) 8.57 (1.10) 5.28 (1.26) 5.33 (1.12)

Frequency 1.88 (0.64) 2.01 (0.74) 3.25 (0.88) 2.90 (0.77)

ELP Accuracy 0.97 (0.03) 0.96 (0.03) 0.96 (0.07) 0.95 (0.06)

Note. All reported values taken from the English Lexicon Project (Balota et al., 2007).

47

Table 2

Mean (and standard error) reading measures for prefixed and suffixed target words across

conditions

Preview condition

Measure Identical Same

stem +

different

affix

Same stem

+ non-affix

Different

stem +

same affix

Unrelated

control

Prefixed target e.g. mistrust pretrust whitrust misnomad outnomad

First fixation duration (ms) 248 (6) 263 (6) 260 (6) 265 (6) 267 (6)

Single fixation duration (ms) 257 (8) 276 (6) 275 (8) 276 (6) 279 (7)

Gaze duration (ms) 315 (10) 321 (8) 320 (9) 327 (8) 331 (10)

Refixation probability .30 (.03) .27 (.03) .26 (.03) .30 (.03) .30 (.03)

Suffixed target e.g. stressful stressary stressard engageful engageous

First fixation duration (ms) 259 (6) 256 (6) 268 (6) 269 (6) 274 (6)

Single fixation duration (ms) 265 (7) 268 (7) 287 (8) 281 (8) 294 (8)

Gaze duration (ms) 321 (10) 338 (10) 344 (10) 347 (11) 358 (9)

Refixation probability .27 (.03) .35 (.03) .33 (.03) .32 (.03) .37 (.03)

48

Table 3

Mean (and Standard Error) Correct RT and Error Rates for the Target Word Stems in

Experiment 2

Target Prime RT (ms) Errors (%)

Prefixed Affixed 586 (3) 2.94 (0.45)

Non-affixed 587 (3) 2.74 (0.48)

Unrelated 597 (4) 4.55 (0.50)

Suffixed Affixed 602 (3) 5.08 (0.56)

Non-affixed 594 (3) 4.54 (0.46)

Unrelated 622 (2) 6.08 (0.56)

49

Figure 1

Example sentences in the boundary paradigm for (1) prefixed and (2) suffixed targets. Prior

to the reader’s eyes crossing the invisible boundary, the preview was either: (a) identical to

target, (b) same stem + different genuine affix, (c) same stem + non-affix, (d) different stem +

same affix, or (e) different stem + different affix (control).

1a. There was a feeling of mutual| mistrust between the two brothers.

1b. There was a feeling of mutual| pretrust between the two brothers.

1c. There was a feeling of mutual| whitrust between the two brothers.

1d. There was a feeling of mutual| misnomad between the two brothers.

1e. There was a feeling of mutual| outnomad between the two brothers.

2a. Students who found the examination| stressful could access help on campus.

2b. Students who found the examination| stressary could access help on campus.

2c. Students who found the examination| stressard could access help on campus.

2d. Students who found the examination| engageful could access help on campus.

2e. Students who found the examination| engageous could access help on campus.