Alexander Pollatsek

The E-Z Reader model of eye-movement control in reading: Comparisons to other models

The E-Z Reader model (Reichle et al. 1998; 1999) provides a theoretical framework for understanding how word identification, visual processing, attention, and oculomotor control jointly determine when and where the eyes move during reading. In this article, we first review what is known about eye movements during reading. Then we provide an updated version of the model (E-Z Reader 7) and describe how it accounts for basic findings about eye movement control in reading. We then review several alternative models of eye movement control in reading, discussing both their core assumptions and their theoretical scope. On the basis of this discussion, we conclude that E-Z Reader provides the most comprehensive account of eye movement control during reading. Finally, we provide a brief overview of what is known about the neural systems that support the various components of reading, and suggest how the cognitive constructs of our model might map onto this neural architecture.

The Interaction of Contextual Constraints and Parafoveal Visual Information in Reading

An experiment is reported which demonstrates that contextual constraints and parafoveal visual information interact during reading. As subjects read sentences, the parafoveal visual information available from a target area in the sentence was varied: the parafoveal information was either visually similar or dissimilar to a target word the subject would later fixate. The visual similarity of the parafoveal preview was factorially combined with the predictability of the target word based on the preceding sentence context. That is, as the subjects made a saccade to the target area, the parafoveal preview was replaced by either a target word that was highly predictable or one that was relatively less predictable from the sentence context. Eye movements and fixation durations were affected both by the visual similarity of the parafoveal information and the target predictability. Moreover, although the visual similarity of the parafoveal preview produced an effect even when the target was not predictable from the context, the effect of parafoveal information was greater when it was predictable. There was also evidence indicating that when the parafoveal information was highly predictable, subjects appeared to use more detailed parafoveal visual information. The results are interpreted within an interactive framework in which lexical representations accumulate activation via both contextual constraint and parafoveal information.

On the use of counterbalanced designs in cognitive research: a suggestion for a better and more powerful analysis.

Counterbalanced designs are ubiquitous in cognitive psychology. Researchers, however, rarely perform optimal analyses of these designs and, as a result, reduce the power of their experiments. In the context of a simple priming experiment, several idealized data sets are used to illustrate the possible costs of ignoring counterbalancing, and recommendations are made for more appropriate analyses. These recommendations apply to assessment of both reliability of effects over subjects and reliability of effects over stimulus items.

Asymmetries in the perceptual span for Israeli readers

Abstract Native Israeli readers read Hebrew and English text as their eye movements were monitored. A window of text moved in synchrony with their eye movements and the window was either symmetrical about the fixation point or offset to the left or right. When subjects were reading Hebrew, the perceptual span was asymmetric to the left and when they were reading English it was asymmetric to the right. The results point out the importance of attentional factors in reading.

Asymmetry of the effective visual field in reading

In three experiments, subjects’ eye movements were recorded as they read from a computer-controlled CRT. The amount of information available to the left and right of the fixation point was varied in order to determine the characteristics of the effective visual field in reading. Experiments 1 and 2 demonstrated that readers do not obtain useful information during a fixation more than 3 or 4 letters to the left of their fixation point. The results of Experiment 3 indicated that the effective visual field does not extend any further to the left than the beginning of the word currently fixated, independent of the number of letters available to the left of fixation. When combined with the results of other research on the perceptual span in reading, the results of these experiments indicate that the effective visual field extends from the beginning of the currently fixated word (but no further than 4 characters to the left of fixation) up to about 15 characters to the right of fixation.

The availability of useful information to the right of fixation in reading

A series of experiments that examined the characteristics of useful information to the right of fixation during reading is reported. In Experiments 1 and 2, reading performance when the information available to the right of fixation was determined by a fixed number of letters was compared with reading performance when the information to the right of fixation was determined by a fixed number of words. Beyond making more letters visible, both experiments showed that preserving all of the letters of a word was of no special benefit to reading. By explicitly presenting parts of the word to the right of fixation as well as the fixated word, Experiments 3 and 4 followed up on the implication that readers utilize partial letter information from words. Both experiments showed that reading was improved by this partial information and that preserving three letters of the word to the right of fixation improved reading almost as much as presenting the entire word. The implications the results have for models of reading are discussed.

Phonological codes are used in integrating information across saccades in word identification and reading

A major issue in reading is the extent to which phonological information is used in visual word perception. The present experiments demonstrated that phonological information acquired on 1 fixation from a word in the parafovea is used to help identify that word when it is later fixated. A homophone of a target word, when presented as a preview in the parafovea, facilitated processing of the target word seen on the next fixation more than a preview of a word matched with the homophone in visual similarity to the target word. This facilitation was observed both in the time to name an isolated target word and in the fixation time on the target word while silently reading a sentence; the preview was virtually never consciously identified in either task. Because the visual similarity of the preview to the target also plays a part in the facilitative effect on the preview, however, codes other than phonological codes are preserved across saccades.

The effects of frequency and predictability on eye fixations in reading: Implications for the E-Z Reader model

Readers read sentences containing target words varying in frequency and predictability. The observed pattern of data for fixation durations only mildly departed from additivity, with predictability effects that were slightly larger for low-frequency than for high-frequency words. The pattern of data for skipping was different as predictability affected only the probability of skipping for high-frequency target words. Simulations of these data using the E-Z Reader model indicated that a single-process model was unlikely to provide a good fit for both measures. A version of the model that assumes that (a) word-encoding time is additively affected by frequency and predictability and (b) difficulty with postlexical processing of the target word causes a double take accounted for the data while indicating that the relationship between the duration of hypothesized word-encoding stages and observed fixation durations is not likely to be transparent.

Covert visual attention and extrafoveal information use during object identification.

Three experiments are reported that examined the relationship between covert visual attention and a viewer’s ability to use extrafoveal visual information during object identification. Subjects looked at arrays of four objects while their eye movements were recorded. Their task was to identify the objects in the array for an immediate probe memory test. During viewing, the number and location of objects visible during given fixations were manipulated. In Experiments 1 and 2, we found that multiple extrafoveal previews of an object did not afford any more benefit than a single extrafoveal preview, as assessed by means of time of fixation on the objects. In Experiment 3, we found evidence for a model in which extrafoveal information acquired during a fixation derives primarily from the location toward which the eyes will move next. The results are discussed in terms of their implications for the relationship between covert visual attention and extrafoveal information use, and a sequential attention model is proposed.

Unspaced text interferes with both word identification and eye movement control.

Subjects read either normal text, text in which the space information between words was absent (either spaces were removed filled with x), or text in which spaces were preserved but the words were flanked by x. In two experiments, reading rate decreased by approx. 50% when space information was not available, suggesting that reading unspaced text is relatively difficult. The removal of space information increased the effect of word frequency on the fixation times for selected target words, indicating that word identification was interfered with by the lack of spaces. In addition, removal of space information influenced the initial landing positions on words, indicating that eye movement control was affected by the absence of spaces. Further analyses were conducted that explored the relationship between these two effects.