Identifying the beast in my breast: More evidence for the influence of inter-word lexical priming on eye movements during reading Kevin Paterson University of Leicester Colin Davis Royal Holloway, University of London Sam McCormack Royal Holloway, University of London Simon Liversedge, University of Southampton

Lexical priming o o Morpho-orthographic similarity between words affects performance in word recognition tasks. o o Are effects similar for words read normally in sentences? o o How does this influence eye movement behaviour? o o Consequences for theories of eye movement control?

Orthographic neighbours o o Widespread view that reading a word activates lexical entry for that word and for orthographically similar words. o o Coltheart et al. (1977) defined a word’s orthographic neighbours as those words that can be formed by substituting one letter for another while preserving letter positions and length. e.g. “tank” has “rank”, “sank”, “task”, etc. as neighbours.

o o Prior exposure to neighbour prime slows target word recognition. o o Masked / covert priming - - Larger effect when prime is of higher frequency than target. - - Effect due to prime supplying strong competitor for target word. o o Unmasked / overt priming - - Larger effects when primes is of lower frequency than target. - - Effect attributed to inhibition of higher frequency competitors when prime is consciously identified. Word recognition research blue blur #### +

Eye movement studies   Words with higher frequency neighbours have longer total reading times and receive more regressions than controls. (Perea & Pollatsek, 1998; see also Pollatsek et al., 1999; Slattery, in press)   Effect may emerge early in eye movement record when the higher frequency neighbour is highly predictable in the sentence context. (Slattery, in press)

Eye movement studies o o Williams et al. (2006) used boundary technique to examine effects of parafoveal preview of a word’s neighbour.   Preview of higher frequency neighbour facilitates target word processing.   Preview facilitates word identification by activating letter representations shared with target. He felt the cold sweet on his face. * He felt the cold sleet on his face. *

Experiment 1 o o Investigated whether neighbour priming effects are observed between words read normally in a sentence. o o Sentences contained either prime-target pairs or control- target pairs matched for length and frequency. o o Primes / controls displayed normally earlier in sentence than targets (mean 1.8 words (7.4 chars) apart). o o Prime was higher or lower in frequency than target (High freq = 316, Low freq = 8, p<.05). Paterson, Liversedge, & Davis, PB&R, 2009.

Stimuli   Low freq prime – high freq target There was a blur prime as the blue target lights spill-over of the police car whizzed down the street. There was a gasp control as the blue target lights spill-over of the police car whizzed down the street.   High freq prime – low freq target In the photograph, the blue prime lights were a blur target against spill- over the cold night. In the photograph, the town control lights were a blur target against spill- over the cold night.

Method & Procedure   Participants’ right eye movements recorded using DPI eye tracker at the University of Leicester.   48 sets of sentences (using word stimuli from Davis & Lupker, 2006).   40 participants from University of Leicester.

Eye Movement Measures o First fixation duration – length of first fixation on word. …to the marsh where... o Single fixation duration – length of fixation on word receiving only 1 fixation.

Eye Movement Measures o Gaze duration – duration of fixations on word first time it is read. …to the marsh where... o Total reading time – duration of all fixations on word.

Prime word Longer gaze durations for lower frequency primes: 17ms effect (Fs>4.8). Interaction not significant. Therefore, evidence that the manipulation of prime word frequency was effective.

Target word Robust inhibitory priming effects at target word were unaffected by prime- target word frequency. First fixation durations: 12 ms effect (Fs>5.8). No interaction (Fs<1). Gaze durations: 15 ms effect (Fs>4.3). No interaction (Fs<1). Total reading times: 45 ms effect (Fs>8.8). No interaction. First fixation durations Gaze durations

Spill-over region   More regressions from post-target region when target follows neighbour prime (Fs>4.9). Interaction not significant.   Evidence that targets that follow neighbour primes are sometimes misidentified?

Summary & Conclusions o Prior exposure to a word’s neighbour earlier in a sentence slows subsequent processing of that word during normal reading. o Effect is observed in eye movement measures associated with early word processing. o Unlike in word recognition research, effect was not modulated by prime-target word frequency. o Eye movements during reading are sensitive to intra- sentential, inter-lexical influences that occur naturally within sentences.

Experiment 2: Morphological Priming o Extended this research by examining inter-word morphological priming effect. o Priming effect turns facilitatory in word recognition studies when prime target words are morphologically related. Semantically transparent marshy / thorny -> marsh Apparent morphological relationship number / really -> numb No morphological relationship extract / justify -> extra Paterson, Alcock, & Liversedge, under review

Example Stimuli o Semantically transparent The forest behind the school had a marshy / thorny path leading to the marsh where the students studied the wildlife. o Apparent morphological relationship If the security man had kept the key number / really safe he would not be numb with sorrow now. o No morphological relationship More time was allowed to extract / justify the extra information that was given.

Method o Participants’ right eye movements recorded using DPI eye-tracker. o 32 participants from University of Leicester. o 54 sets of prime and target words (18 of each type).

Early target word processing o Priming effect in first fixation durations for semantically transparent morphological primes only.

Later target word processing o Same pattern in gaze durations and total reading times as in first fixation durations. o Effect for semantically transparent primes only.

Reading time effect o Word identification facilitated by semantically related morphological primes only. o Effect emerged in eye movement measures that reflect early word processing,so it appears that prior exposure to a morphologically complex word can facilitate early processing of a semantically related stem. o Pattern similar to that observed in unmasked priming – in both cases prime is available for conscious identification prior to fixation on target word.

Eye Movement Measures o Skipping – percentage probability of skipping word. o Regressions – percentage probability of regression. …to the marsh where...

o Higher word-skipping rates for target words that follow primes than controls.

Word Skipping effects o Widely argued that word-skipping effects occur when word can be identified in parafoveal vision (e.g., Binder et al., 1999; Brysbaert et al., 2005). o It appears that exposure to prime facilitated parafoveal processing of target, to extent that it was more likely to be identified (or misidentified) in parafoveal vision. o Word skipping often followed by regression, which has been attributed to error-correcting procedure (Drieghe et al., 2004; Brysbaert et al., 2005).

o More regressions from post-target region when target word follows prime than control.

Skipping and regression effects o Also, more regressions when targets were skipped (38%) than when they received first-pass fixation(24%). o Findings are consistent with targets that follow primes sometimes being misidentified in parafoveal vision and subsequent detection of misidentification triggering a regression. o Evidence for early orthographic priming effect in parafoveal processing of word targets.

Conclusions o Two clear effects: orthographic priming effect on parafoveal word processing, and semantically mediated morphological priming effect in target word reading times. o Brief experience of processing a word can carry across intervening words to influence lexical processing of another word later in same sentence. o This is turn rapidly influences eye movements, and so inter-word priming effects may have an important influence on eye movement control.

What is the source of this inter- word lexical priming effect?

What Colin might say… Effect is due to spreading activation in the mental lexicon. A prime word activates its lexical entry and lexical entries for related words. This activation decays over time. However, there is sufficient ongoing activation to produce orthographic priming.

What Erik might think… This is an episodic memory effect. When prime and target words are read separately, target word processing evokes an episodic memory trace encoded during prime word processing, and this affects word identification.

How to test these ideas? o Spreading activation effects should be short-lived and dissipate rapidly across intervening words. o Episodic effects should be longer-lasting. o Therefore, valuable to determine if inhibitory priming is affected by the number of intervening words in sentences.

Experiment 3   Examined 2 questions: Are inhibitory priming effects observed for addition and deletion neighbours? (e.g., Davis, Perea, & Acha, (In press) public-pubicbeast-breast 2. Do effects occur for prime-target pairs that are either close together or further apart in sentences?

stimuli Close prime-target pairs The beast prime at his breast target looked scary and was desperate for a meal The snake control at his breast target looked scary and was desperate for a meal. Distant prime-target pairs The beast prime that sat quivering at his breast target looked scary and was desperate for a meal The snake control that sat quivering at his breast target looked scary and was desperate for a meal.

Method & Procedure   Participants’ right eye movements recorded using DPI eye tracker at the University of Leicester.   60 sets of sentences.   40 participants from University of Leicester.

Target Word Reading Times Inhibitory priming effect in first fixation durations for close prime-target pairs only. Stronger inhibitory priming effect for close prime-target pairs in gaze durations. Similar pattern in total reading times.

Spill-over Region Effects No priming effects in first fixation durations or first-pass reading times (Fs<2.3). However, longer total reading times and more regressions from this region when target followed either a close or distant neighbour prime.

Conclusions o Evidence that prior exposure to higher frequency addition/deletion neighbour during reading can impede word processing. o Evidence for priming effects for both close and distant prime-target pairs, although these effects emerge in different eye movement measures. o Effect for close prime-target pairs emerges in measures of early word processing (in first fix and gaze durations for target word). o Effect for distant prime-target pairs appears in measures of later word processing (total reading times and regressions for post- target word).

Conclusions o Consistent with operation of spreading activation and episodic priming effects? o Powerful inhibitory priming effects for close prime-target pairs because of residual activation in prime word’s lexical entry? o Weaker interference effects for distant prime-target pairs because activation has dissipated over intervening words, leaving only episodic effect?

Consequences for EM models? o Current eye movement models such as E-Z Reader and SWIFT do not include mechanisms that allow for inter- word lexical priming effects. o Models need to be further developed to provide explanation of the effect of higher order processes on eye movements during reading, including inter-word priming. o Future research needs to establish full extent of inter- word priming and degree to which effects carry across intervening words in a sentence ( see also Forster, 2009, for research on masked priming effects that carry across intervening words ).