Sixty-six college students read two chapters from a contemporary novel while their eye movements were monitored. The eye movement data were analyzed to identify factors that influence the location of a reader's initial eye fixation on a word. When the data were partitioned according to the location of the prior fixation (i.e., launch site), the distribution of fixation locations on the word (i.e., landing site distribution) was highly constrained, normal in shape, and not influenced by word length. The locations of initial fixations on words can be accounted for on the basis of five principles of oculomotor control: A word-object has a specific functional target location, a saccadic range error occurs that produces a systematic deviation of landing sites from the functional target location, the saccadic range error is reduced somewhat for saccades that follow longer eye fixations, there exists oculomotor variability that is a second, non-systematic source of error in landing sites, and the oculomotor variability increases with distance of the launch site from the target.

Previous research has found that words are identified most quickly when the eyes are near their center (the Optimal Viewing Position effect). A study was conducted to determine whether this same phenomenon is observed during reading, as revealed by a relationship between fixation position in a word and the duration of the fixation. An analysis of three large existing corpora of eye movement data, two from adults and one from children, showed a surprising inverted Optimal Viewing Position curve: mean fixation duration is greatest, rather than lowest, when the eyes were at the centers of words. From this phenomenon, we suggest an alternative explanation to the fixation duration trade-off effect in word refixations [O'Regan & Lévy-Schoen, Attention and performance XII: the psychology of reading (1987)]; the phenomenon also contradicts expectations of both oculomotor and cognitive theories of eye movement control. Attempts to test alternative explanations led to the discovery of another phenomenon, the Saccade Distance effect: mean fixation durations vary with the distance of the prior fixation from the currently-fixated word, being longer with greater distances. The durations of fixations in reading are complexly determined, with influences both from language and perceptual/oculomotor levels.

An analysis of over 40,000 eye fixations made by college students during reading indicates that the frequency of immediately refixating a word following an initial eye fixation on it varies with the location of that fixation. The refixation frequency is lowest near the center of the word and positively accelerating with distance from the center. The data are well fit by a parabolic function. Assuming that refixation frequency is related to the frequency of successful word identification, the observed curvilinear relation results naturally from models that postulate a linear decrease in acuity with retinal eccentricity. A single letter difference in fixation location in a word can make a sizeable difference in the likelihood of refixating that word. The effects of word length and cultural frequency on the frequency of refixating are also examined.McConkie, Kerr, Reddix, Zola, & Jacobs EYE MOVEMENT CONTROL DURING READING: II. FREQUENCY OF REFIXATING A WORDDuring reading, people fixate more frequently near the centers of words than near the beginnings and ends (Rayner, 1979). O'Regan (1981) proposed a Convenient Viewing Position hypothesis, stating that readers learn to send their eyes to the centers of words because, across the words in a language, that location is optimal for word identification. Due to the rapid drop in visual acuity with distance from the center of the fovea, together with the fact that letters bounded by spaces are more perceptible (Bouma, 1978;Jacobs, 1987), the letters of a word are maximally identifiable when the eyes are near the word's center. O'Regan further suggested that the further the eyes lie from the Convenient Viewing Position, the greater the probability that a second eye fixation on the word will be required for identification. This prediction was confirmed in a word identification study (O'Regan, 1984), which found that the frequency of making a second fixation on a word is minimized when the initial fixation is near the center of that word. Furthermore, the frequency of refixating increases as the distance of the first fixation from the center of the word increases. We refer to this relationship as the Word Refixation Frequency Curve, or simply as the word refixation curve. The existence of a word refixation curve in word identification tasks has been replicated (O'Regan, Levy-Schoen, Pynte, & Brugaillere, 1984) and there is some evidence that it may also be present in the eye fixation pattern made during reading (Blanchard & McConkie, cited by O'Regan & Levy-Schoen, 1987).