Eye-movement parameters and pattern discrimination

Abstract

Fig. 1. Schematic of stimulus. Stimuli always contained a center standard pattern surrounded by eight other patterns of asterisks, some of which matched the standard (called targets) and some of which differed from the standard (called nontargets).Second, the effects on eye-movement parameters of the size of the matrix from which patterns were generated was assessed. Patterns were generated from 4 by 4, 6 by 6, 8 by 8, and 10 by 10 matrices. The larger the matrix size, the larger the average number of elements in a pattern. The results of this study showed clearly-perhaps surprisingly-that pattern discrimination was not affected by these variations in matrix size.Third, the effect on eye-movement parameters of the variations in the number of elements in a pattern of a particular matrix size was evaluated. The results of the study showed that variations in the number of elements in target patterns of a particular matrix size affected eye movement parameters differently than did variations in the number of elements in nontarget patterns of the same matrix size. A target pattern was nearly always fixated foveally, whereas the probability of looking directly at a nontarget pattern depended upon its "similarity" to the standard pattern. Duration of fixation on a pattern, however, was determined both by variations in target patterns and by variations in nontarget patterns.Fourth, an attempt was made to identify the features or variations in patterns, in addition to those specifically manipulated in this experiment, that most affect human pattern discrimination. There presently exists no universal psychophysics of pattern perception. That is, although the three physical variables of intensity, wavelength, and purity account well for the perception of homogeneous visual fields, the physical variables that account for the perception of patterned visual fields have not been satisfactorily identified. This is true even though 1~200

Implications of measurement of eye fixations for a psychophysics of form perception

“…2, 3, and 4) confirm the previous fmdings that Ss do fixate for different durations at different locations (Mackworth & Morandi, 1967;Gould & Dill, 1969). They also extend the previous fmdings by indicating that Ss differentially fixate within the silhouettes of the type of figures that have often been used in form-perception studies.…”

“…It has been shown that, when confronted with patterns, especially large ones, Ss tend to fixate successively on more than one element, in a systematic fashion related to the individual stimulus and to the elements within it that contain the most information (Mackworth & Morandi, 1967;Gould & Dill, 1969). The studies cited, unlike the one to be described.…”

“…Gould and Dill (1969) suggest that the duration of fixation is determined by the time it takes to process the encoded information. The time is spent comparing the encoded elements with the standard prototype.…”

Focal and nonfocal processing of color and form

“…The ability to Ss to extract a limited amount of infonnation from stimuli which are not being fixated (i.e., stimuli which project outside of the foveal area of the retina) has been reported by Sanders (1970), Gould and Dill (1969), and Williams (1967). In the study by Gould and Dill, Ss determined how many of the eight test patterns matched a standard pattern while frequency and duration of eye fixations were recorded.…”

“…Studies of eye movements made during a task involving visual search and pattern discrimination (Gould & DilL 1969) indicate that stimuli can be discriminated grossly in the periphery of the eye and only require foveal foxation for finer discriminations. A related study by Williams (I967) found that Ss selected objects in the extrafoveal field much better on the basis of color than on the basis of size or shape.…”