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

2. 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

3. 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.

4. 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.

5. 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 (~ ms post-stimulus).

6. 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.

7. 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

8. 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.”

9. 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.

10. 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)

11. 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.

12. 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)

13. Single Fixation Data Significant 26 ms main effect of frequency
F1 (1,63) = 104, p < ; F2 (1,43) = 148, p <
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.

14. 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)

15. 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.

16. 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

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

18. 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.

19. Thanks
Sara Sereno
Paddy O’Donnell
Sébastien Miellet