S. M. Luria

Comparison of Eye Movements over Faces in Photographic Positives and Negatives

Eye movements were recorded while subjects viewed ordinary portraits and photographic negatives of those portraits. Under both conditions they first studied sixteen portraits and then tried to decide which of forty-eight portraits they had just seen. They made more errors of recognition while viewing negatives, and their fixation patterns were significantly altered: there was a decrease in the percentage of fixations directed to the eyes, nose, and mouth, and an increase for such details as the ears, cheeks, chin, cap, and necktie. There was also a decrease in the ratio of fixations to the most fixated detail compared to the least fixated detail.

Eye movements during search for coded and uncoded targets

Eye movements and search time of four subjects were studied as they searched for a target dial in a 4 х 4 array of dials which were differentiated by (1) color, (2) shape, (3) a combination of color and shape, or (4) were uncoded. Subjects did not exhibit a characteristic scanpath, and method of scanning did not relate to search time. Search time varied reliably among conditions; it was generally shortest in the color condition, followed by color shape, shape, and the uncoded condition. Subjects were capable of using both shape and color simultaneously. Search time was strongly associated with the average number of fixations required for target detection but not with other measures of eye movements. Fixation duration was a particularly inconsistent measure.

Conflicting visual and tactual-kinesthetic stimulation

The relative importance placed on visual rather than tactual or kinesthetic cues was investigated under water. In matching disks of various sizes to common coins from memory, Ss consistently chose disks much smaller than the actual size of the coins and more closely approximating their optical size in the water, even when permitted to see their own hands. In a second experiment, the performance of a motor task, learned to criterion while blindfolded, was significantly more disrupted under water than in air when Ss were permitted to look. Both sets of results demonstrate the dominance of vision over the other two senses. The importance of the underwater environment as a naturally distorted one, requiring no lenses or prisms to produce optical distortions, is emphasized.

Visibility of colors underwater.

The underwater visibility of various colors, both fluorescent and nonfluorescent, was measured in four different bodies of water. The waters were selected to sample the continuum from very murky to clear. SCUBA divers observed with a horizontal path and other subjects on the surface looked down vertically. Fluorescent colors were always more visible than nonfluorescent, but the specific colors that were easiest and most difficult to see depended upon the body of water.

Performance and preference with various VDT phosphors.

Subjects searched for target letters and symbols in VDT displays produced with green, amber, yellow, red, blue, and white phosphors. The green was rated more highly than yellow, and blue was rated worst. There were no significant differences in search time, but there were significant differences in the number of errors made with different phosphors. Yellow produced the fewest errors and white the most. Speed and accuracy did not correlate with the preference ratings for the various phosphors.

Visual evoked responses elicited by rapid stimulation

Abstract An assessment of the technique of eliciting VERs with rapid rates of stimulation has revealed that differences in evoked response due to stimulus parameters may be minimized under these conditions. The probable reason is that addition of ongoing activity from one flash to that elicited by another occurs; this addition can obscure or enhance wave form differences present in the complete evoked response. A comparison of visual-evoked responses (VERs) to rapid flash rates which were empirically determined with VERs synthesized from a linear addition of the first two segments of the complete evoked response reveals a rather remarkable agreement in most cases. On the other hand, some failures to predict empirical data in this manner to occur. These failures are not due to temporal variations and their etiology is unknown at this time. Until the electrogenesis of the VER is understood, we conclude the use of both a fast and a slow rate to obtain VERs is a good methodological technique for studying brain functioning.

Effect of turbidity on judgments of distance underwater.

Judgments of the distance of an underwater target at various locations were obtained as a function of water-clarity. When the target was close to S, its distance was underestimated. Judgments changed to overestimation as the actual physical distance was increased. Estimates were invariably greater in turbid water than in clear water. These data resolve the apparent conflict between expectations from optical considerations and actual distance estimates made in natural waters.

The effects of set size on color matching using CRT displays

The time required to match a colored stimulus to one of a set of colors was measured as a function of color sets ranging in size from 2 to 10. Reaction time (RT) increased linearly with increases in set size to 5 or 6, after which the increase, although still linear, was less steep. Error rate increased sharply with set sizes of 8, 9, and 10. The relative RTs to the different colors remained constant despite changes in the experimental method.

Techniques for analysing differences in vers: Colored and patterned stimuli

Abstract Statistical and experimental techniques for analysis of visual evoked responses (VERs) to colored and patterned stimuli were compared. Statistical analysis of the amplitudes and latencies of components was effective in evaluating subtle differsences among VERs, such as different responses to hues by color normal and color defective individuals. For gross changes in VER, as an found Drift patterned versos blank fields, an experimental technique was preferable. This consists of summing the responses to one stimulus and subtracting the same number to another. A distinct pattern element was extracted by this technique which was similar for all colors.

The Perception of Depth Contours with Yellow Goggles

The ability of subjects to discriminate the depth of depressions in the snow was conducted at a cross-country ski area. The percentage of correct judgments on an overcast day was significantly greater with yellow goggles than with luminance-matched neutral goggles. This experiment, suggested by the chromatic—achromatic theory of color vision, indicates why yellow goggles are popular despite many previous unsuccessful attempts to prove their effectiveness.