Investigating the combined effects of word frequency and contextual predictability on eye movements during reading Christopher J. Hand Glasgow Language Processing

Background The ease or difficulty associated with processing a word influences when the eyes move from one fixation to another. Two higher-level linguistic variables in particular influence eye movements (EMs) during reading Word frequency Contextual predictability

Effects of word frequency on EMs during reading Words can be defined as high or low frequency (HF or LF) depending on how often they occur in natural text. LF words are fixated longer than HF words Inhoff & Rayner, 1986; Just & Carpenter, 1980; Raney & Rayner, 1995; Rayner & Raney, 1996; Rayner & Duffy, 1986; Rayner, Sereno, & Raney, 1996; Rayner, Ashby, Pollatsek & Reichle, 2004; Rayner, Fischer & Pollatsek, 1998; Sereno & Rayner, 2000.

Effects of contextual predictability on EMs during reading Words that are more constrained by prior context (i.e., predictable) are read quicker than words that are less constrained (i.e., unpredictable). Balota, Pollatsek & Rayner, 1985; Binder, Pollatsek & Rayner, 1999; Ehrlich & Rayner, 1981; Rayner et al., 2004; Rayner & Well, 1996.

Examining the effects of word frequency and predictability simultaneously Reaction Time Studies Stanovich & West (1979, 1983) West & Stanovich (1982) Typically reported an interactive pattern of frequency and predictability effects Event-Related Potential (ERP) Study Sereno, Brewer, & O’Donnell (2003) Evidence to suggest an interaction between frequency and context in the early N1 ERP component (~132-192 ms post-stimulus).

Examining the effects of word frequency and contextual predictability simultaneously Few EM studies have examined the joint effects of frequency and predictability as their principal focus A frequency × predictability interaction on EM behaviour during reading suggests that these variables affect the same stage of processing. Word frequency affects early lexical processing Sereno & Rayner, 2000 Debate as to whether context affects early, lexical processing or later, post-lexical processing. Important for models of EM control in reading.

However, Rayner et al.’s (2004) study had perceived limitations Examining the effects of word frequency and contextual predictability simultaneously Rayner et al. (2004) Reported no interaction on target word fixation time measures However, Rayner et al.’s (2004) study had perceived limitations Few experimental items per condition Short length of pre-target context

Present Study 88 experimental items vs. 32 (Rayner et al., 2004) 22 HF-predictable “Callum was having trouble with his homework. He asked his uncle who was a teacher to help him with the assignment.” 22 HF-unpredictable “Ingrid’s boiler had suddenly broken down. Fortunately, her neighbour’s father was a plumber and would be able to help.” 22 LF-predictable neighbour’s father was a teacher and would be able to help.” 22 LF-unpredictable uncle who was a plumber to help him with the assignment.”

Present Study Items had a maximum length of 120 characters (inc. spaces and punctuation) vs. 72 characters maximum in Rayner et al. (2004). Argued that it is more appropriate to use longer contexts preceding target words in order for the effects of context to fully develop.

Present Study Subjects Method 64 participants Native English speakers No serious reading disorders, i.e., dyslexia. Method Dual-Purkinje eye tracker (Generation 5.5) Materials displayed over two lines of visual display (maximum line length 60 character spaces)

Results 3.6% of total experimental trials were rejected due to track losses or excessive blinking A 2 (frequency; high, low) × 2 (context; predictable, unpredictable) analysis of variance was performed both by participants and items A range of standard EM measures were examined First fixation duration (FFD), single fixation duration (SFD), gaze duration (GD), total time (TT), probability of fixating the target, and spillover fixation duration.

Target Word Fixation Time Data For FFD, SFD, GD and TT, highly significant main effects of word frequency and predictability were found by both participants and items However, no evidence of an interaction was found on these measures (all Fs < 1)

Single Fixation Data Significant 26 ms main effect of frequency F1 (1,63) = 104, p < 0.0001; F2 (1,43) = 148, p < 0.0001. Significant 10 ms main effect of predictability F1 (1,63) = 13.8, p < 0.001; F2 (1,43) = 12.1, p < 0.01. No evidence of interaction Both Fs < 1.

Discussion An interaction between frequency and predictability effects may be an elusive effect, that does not manifest itself in the EM record. However, research has demonstrated that the ability to extract information from words viewed parafoveally is influenced by the frequency and predictability of that parafoveal word Inhoff & Rayner (1986) Balota et al. (1985)

Parafoveal processing It may be the case that parafoveal preview operates in conjunction with the effects of frequency and predictability. Parafoveal preview typically manipulated by gaze-contingent display change paradigms Parafoveal preview benefit can also be indexed dependent on the distance of the fixation prior to fixating the target word and the beginning of the target word.

Frequency × Predictability × Launch Site Initial re-analysis of the EM data from this experiment, contingent on parafoveal preview has yielded some interesting results… Significant three-way interaction between frequency, predictability and launch site SFD – F1 (2,63) = 7.19, p < 0.01; F2 (2,43) = 7.49, p < 0.01 Similar patterns for FFD, GD and TT

Frequency × Predictability × Launch Site – Single Fixation Duration Launch site Frequency Predictability Freq × Pred 1-3 chars p<0.0001 p<0.0001 p<0.05 4-6 chars p<0.0001 p=0.10 p<0.01 7-9 chars p<0.01 F<1 F<1

Conclusion The finding of an interactive pattern of effects when parafoveal preview is accounted for provides clear evidence of predictability effects at an early, lexical stage of processing. Accurately delineating the precise time-course of the effects of contextual predictability has important consequences for models of EM control during reading and will aide resolve contention between equivocal theories of language processing.

Thanks Sara Sereno Paddy O’Donnell Sébastien Miellet