Françoise Vitu

Optimal landing position in reading isolated words and continuous text

During isolated-word reading, within-word eye-movement tactics (i.e., whether the eye makes one or more fixations on the word) depend strongly on the eye’s-first fixation position in the word; there exists an optimal landing position where the probability of having to refixate the word is much smaller than when the eye first fixates other parts of the word. The present experiment was designed to test whether the optimal landing position effect still exists during text reading, and to compare the nature and strength of the effect with the effect found for isolated words. The results confirmed the existence of an optimal landing position in both reading conditions, but the effect for words in texts was weaker than it was for isolated words, probably because of the presence of factors such as reading rhythm and linguistic context. However, the effect still existed in text reading; within-word tactics during text reading are dependent on the eye’s initial landing position in words. Moreover, individual fixation durations were dependent on within-word tactics. Thus, the initial landing position in words must be taken into account if one wishes to understand eye-movement behavior during text reading. Further results concerned the effects of word length and word frequency in both reading conditions.

Word skipping: implications for theories of eye movement control in reading

This chapter provides a meta-analysis of the factors that govern word skipping in reading. It is concluded that the primary predictor is the length of the word to be skipped. A much smaller effect is due to the processing ease of the word (e.g., the frequency of the word and its predictability in the sentence).

Mindless reading: Eye-movement characteristics are similar in scanning letter strings and reading texts

The purpose of the present study was to compare the oculomotor behavior of readers scanning meaningful and meaningless materials. Four conditions were used—a normal-text-reading control condition, and three experimental conditions in which the amount of linguistic processing was reduced, either by presenting the subjects with repeated letter strings or by asking the subjects to search for a target letter in texts or letter strings. The results show that global eye-movement characteristics (such as saccade size and fixation duration), as well as local characteristics (such as word-skipping rate, landing site, refixation probability, and refixation position), are very similar in the four conditions. The finding that the eyes are capable of generating an autonomous oculomotor scanning strategy in the absence of any linguistic information to process argues in favor of the idea that such predetermined oculomotor strategies might be an important determinant of eye movements in reading.

Eye Movement Control during Reading: Foveal Load and Parafoveal Processing:

We tested theories of eye movement control in reading by looking at parafoveal processing. According to attention-processing theories, attention shifts towards word n+1 only when processing of the fixated word n is finished, so that attended parafoveal processing does not start until the programming of the saccade programming to word n+1 is initiated (Henderson & Ferreira, 1990; Morrison, 1984), or even later when the processing of word n takes too long (Henderson & Ferreira, 1990). Parafoveal preview benefit should be constant whatever the foveal processing load (Morrison, 1984), or should decrease when processing word n outlasts an eye movement programming deadline (Henderson & Ferreira, 1990). By manipulating the frequency and length of the foveal word n and the visibility of the parafoveal word n+1, we replicated the finding that the parafoveal preview benefit is smaller with a low-frequency word in foveal vision. Detailed analyses, however, showed that the eye movement programming deadline hypothesis could not account for this finding which was due not to cases where the low-frequency words n had received a long fixation, but to cases of a short fixations less than 240 msec. In addition, there was a spill-over effect of word n to word n+1, and there was an element of parallel processing of both words. The results are more in line with parallel processing limited by the extent to which the parafoveal word processing on fixation n can be combined with the foveal word processing on fixation n+1.

The influence of parafoveal preprocessing and linguistic context on the optimal landing position effect

Several experiments have shown the existence of an optimal landing position effect during isolated word recognition as well as during text reading; both the probability of refixating the test word and the gaze duration are smaller if the eye first fixates near the center of the word than if the eye first fixates other positions in the word. However, recent data indicate that the optimal landing position effect is weakened under normal reading conditions, when words are included in texts. The purpose of the present experiment was to test whether parafoveal preprocessing or linguistic context specific to the text reading situation could be responsible for this weakening. With a paradigm that approximates normal reading, albeit in & somewhat slower manner, it was shown that although the possibility of preprocessing words in parafoveal vision and of predicting them from preceding context globally affected refixation probability and gaze duration on the word, this did not strongly affect the optimal landing position effect. Since the global effects of these factors were comparable to those found by other authors in normal reading, it was concluded that the weakening of the optimal landing position effect during text reading results from the influence of other factors peculiar to this situation. Hypotheses are proposed as explanations of the effects of the manipulated factors on oculomotor behavior.

The Pupillary Light Response Reveals the Focus of Covert Visual Attention

The pupillary light response is often assumed to be a reflex that is not susceptible to cognitive influences. In line with recent converging evidence, we show that this reflexive view is incomplete, and that the pupillary light response is modulated by covert visual attention: Covertly attending to a bright area causes a pupillary constriction, relative to attending to a dark area under identical visual input. This attention-related modulation of the pupillary light response predicts cuing effects in behavior, and can be used as an index of how strongly participants attend to a particular location. Therefore, we suggest that pupil size may offer a new way to continuously track the focus of covert visual attention, without requiring a manual response from the participant. The theoretical implication of this finding is that the pupillary light response is neither fully reflexive, nor under complete voluntary control, but is instead best characterized as a stereotyped response to a voluntarily selected target. In this sense, the pupillary light response is similar to saccadic and smooth pursuit eye movements. Together, eye movements and the pupillary light response maximize visual acuity, stabilize visual input, and selectively filter visual information as it enters the eye.

Regressive Saccades and Word Perception in Adult Reading

Three explanations for the occurrence of regressive eye movements during reading are described. Predictions are derived from one of these, the word identification explanation. These predictions are tested by analyzing a large corpus of eye movement data from 4 adult readers. The likelihood of regressing is directly related to the length of the prior saccade and to the probability the saccade skipped a word. The likelihood of regressing to a skipped word is influenced by variables that affect the perceptibility of that word. The likelihood of making inter- and intra-word regressions are often affected differently by the variables studied, indicating the importance of maintaining this distinction. The results are generally compatible with a word identification explanation of regressions during reading, though this is probably not the only basis on which regressive saccades occur.

On the limited role of target onset in the gap task: Support for the motor-preparation hypothesis

Saccade latency is reduced when the fixation stimulus is removed shortly before a saccade target appears (gap task) as compared to when the fixation stimulus remains present (overlap task). To test the assumption that this gap effect benefits from advanced motor preparation (M. Paré & D. P. Munoz, 1996), we manipulated target onset independently of the signal to launch a saccade (peripheral offset at the mirror location). In Experiment 1, we showed that, when the target appears at one of only two possible locations, target onset strongly improves performance (lower latency, higher accuracy) in the overlap task but not in the gap task. In Experiment 2, we found that the lack of an effect of target onset in the gap task was not due to inhibition of a reflexive response to the transient associated with the offset (go signal) in our task. In Experiment 3, we manipulated target onset and target uncertainty (two, four, or eight potential target locations) in gap and overlap tasks. As target uncertainty increased, the gap effect decreased, and the effect of target onset on saccade latency in the gap condition became greater. Overall, our results suggest, in line with the motor-preparation hypothesis, that saccade metrics in a gap task are computed before the target is actually displayed and that advanced motor preparation is enhanced when the location of the target is predictable. Analyses of anticipations and regular-latency errors corroborated this view.

Eye movements in reading isolated words: evidence for strong biases towards the center of the screen.

Three experiments were conducted that compared the eye movement pattern to a peripheral word or letter string as a function of the position of an initial fixation stimulus relative to the center of the screen and the straight-ahead position. Results revealed a strong bias of the eye behavior towards the center of the screen, but not towards the straight-ahead position. Saccades were greater in length, and landed closer to the center of words/strings when launched from a position left of center than when launched from either center or right part of the screen. In addition, the initial saccade launch site was deviated to the right, or to the left of the initial fixation stimulus depending on where relative to the center of the screen the fixation stimulus was displayed. Data were interpreted with the assumption that saccades are programmed in a visual reference framework, with saccade amplitude being computed in relative coordinates. Further research will determine whether the observed bias generalizes to text reading.

A test of parafoveal‐on‐foveal effects with pairs of orthographically related words

One of the main controversies in the field of eye movements in reading concerns the question of whether the processing of two adjacent words in reading occurs in sequence, or in parallel. To distinguish between these views, the present experiment tested the presence of parafoveal‐on‐foveal effects with pairs of orthographically related words (or neighbours that differed by a single letter) in a controlled but reading‐like situation. Results revealed that fixation times on a foveal target word were shorter when the target was accompanied by an orthographically similar parafoveal word than when the parafoveal word was dissimilar. Furthermore, the size of the effect tended to vary with both the relative frequency of target and parafoveal words, and the position of the critical letter. These results were interpreted in the framework of a pure parallel processing hypothesis, where the processing of adjacent words is only limited by visual acuity, and the respective lexical properties of the foveal and parafoveal words.