Academic journal article Psychonomic Bulletin & Review

The Eyes Fixate the Optimal Viewing Position of Task-Irrelevant Words

Academic journal article Psychonomic Bulletin & Review

The Eyes Fixate the Optimal Viewing Position of Task-Irrelevant Words

Article excerpt

We evaluated whether one's eyes tend to fixate the optimal viewing position (OVP) of words even when the words are task irrelevant and should be ignored. Participants completed the standard Stroop task, in which they named the physical color of congruent and incongruent color words without regard to the meanings of the color words. We monitored the horizontal position of the first eye fixation that occurred after the onset of each color word to evaluate whether these fixations would be at the OVP, which is just to the left of word midline. The results showed that (1) the peak of the distribution of eye fixation positions was to the left of the midline of the color words, (2) the majority of the fixations landed on the left side of the color words, and (3) the average leftward displacement of the first fixation from word midline was greater for longer color words. These results suggest that the eyes tend to fixate the OVP of words even when those words are task irrelevant.

When an individual intentionally reads a word, the eyes tend to land on a specific location on the word, known as the optimal viewing position (OVP; Dunn-Rankin, 1978; O'Regan, 1981; Rayner, 1979). The OVP is just to the left of the center of the word, and the available data suggest that it tends to be farther left of center for longer words (O'Regan, Lévy-Schoen, Pynte, & Brugaillère, 1984). When the eyes fail to land on the OVP, intentional reading is slowed by approximately 20 msec for each deviation in letter position from the OVP (O'Regan & Jacobs, 1992). Here, we evaluated whether the eyes are biased to fixate the OVP even when the word is irrelevant to the task at hand and the demands of the task require lexical processing of the word to be suppressed.

To address this issue, we monitored eye position while participants completed the standard Stroop task (Stroop, 1935). In the Stroop task, participants are shown a color word (e.g., red) in a physical color that is either congruent (e.g., red) or incongruent (e.g., blue) with the color word. Participants are required to suppress lexical processing of the color word and to name the physical color. The standard result is that participants are much slower to name the physical color when that color is incongruent than when it is congruent with the meaning of the color word (see MacLeod, 1991, for a review). This result is often taken to indicate that the meaning of the color word is processed even though it is irrelevant to the task. We reasoned that if the oculomotor system is engaged by these task-irrelevant words, the eyes might fixate to the left of center (the OVP) of the colored words, even though participants are trying to suppress lexical processing of the color word and to name the physical color instead.

There are several good reasons to believe that the eyes might fixate the OVP of words even when the words are task irrelevant. One reason is that word reading is a highly practiced task. As such, it seems reasonable that the stereotypic eye movements associated with intentional reading might generalize to situations in which word reading is detrimental to task performance. Another reason is suggested by recent studies of single-letter coloring in the Stroop task. When a single letter of a Stroop word is colored, the Stroop effect is radically reduced, and sometimes completely eliminated (e.g., Besner, Stolz, & Boutilier, 1997; Manwell, Roberts, & Besner, 2004). In a recent report, Parris, Sharma, and Weekes (2007) extended these findings by examining how the magnitude of the Stroop effect varied as a function of the position of the letter that was colored. In one of their studies, Parris et al. colored the initial letter, the final letter, the letter to the right of center, or-critically-the letter just to the left of center, which approximated the OVP. The Stroop effect observed in these conditions was also compared with the effect observed in a condition in which all of the letters were colored, as in the standard Stroop task. …

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