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The present paper describes a training procedure that can be used to obtain contrast-sensitivity functions in a single session with monkeys (Macaca mulatto). Examples of these functions, obtained early in the testing phase of the procedure, are presented. For comparison, the functions obtained from several human volunteers performing the same procedure are also shown. The resulting methodology is versatile enough to use in a variety of sensory systems with only minor modifications.

It has been common in the history of psychology to think of reading as involving two sets of processes, one that makes visual information available (perceptual processes) and the other that makes use of that information in support of the language processes involved in reading (cognitive processes). Interactive theories of reading (Rumelhart, 1977) have questioned the usefulness of such a distinction, suggesting that each processing activity occurs in the environment of, and can be subject to influences from, all other processing taking place. Recent work, however, has suggested the existence of different processing modules that are not directly influenced by the products of some other processing activities (Fodor, 1983; Frazier & Fodor, 1978). In particular, it has been proposed that the visual processes that make information available are not influenced by higher level processes (Forster, 1979; Stanovich, 1980). This chapter presents some data from a study we have conducted that supports the utility of maintaining a distinction in theories of reading between perceptual processes that make visually-provided information available and cognitive processes that use this information for the purposes of the task at hand.

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, 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 visual information 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.

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 perceptuo-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 perceptuo-oculomotor variability that is a second, nonsystematic source of variation in landing sites, and the perceptuo-oculomotor variability increases with distance of the launch site from the target.