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Biomedical subjects

D J Aks

Publications and source records attributed to D J Aks.

5 recordsLinked to original sources
PubMed1998

Influence of exercise on visual search: implications for mediating cognitive mechanisms.

The present study investigated the influence of exercise on a feature and conjunction search performed by 10 women and 8 men. We compared the effect of 10 min. of low- (65% work load) and high-exertion cycling (8 min. at 65% work load plus 2 min. at 85% work load) on response time, accuracy and response time as a function of the number of items in the display (slopes). Analysis showed faster search and increased slopes following exercise, suggesting that exercise improved performance especially under conditions of focused attention. The lowest response times followed high-exertion exercise, and most focused search, i.e., largest slopes, followed exercise of low-exertion.

Adult↗
PubMed1996

Visual search for size is influenced by a background texture gradient.

Research on the perception of texture gradients has relied heavily on the subjective reports of observers engaged in free-viewing. We asked whether these findings generalized to speeded performance. Experiment 1 showed that an important aspect of subjective perception--size-constancy scaling with perceived distance--also predicted the speed of pop-out visual search for cylinders viewed against a texture gradient. Experiment 2 showed that this finding could not be attributed to the local contrast between search items and the background texture. Experiment 3 assessed the relative contributions of 2 separable dimensions of texture gradients--perspective (radial spreading) and compression (foreshortening)--finding them to be independent in the more rapid search conditions (long target shorter distractors) but combined in the influence in the slower conditions (short target longer distractors).

Adolescent↗
PubMed1992

Visual search for direction of shading is influenced by apparent depth.

Recent reports of rapid visual search for some feature conjunctions suggested that preattentive vision might be sensitive to scene-based as well as to image-based features (Enns & Rensink, 1990a, 1990b). This study examined visual search for targets defined by the direction of a luminance gradient, a conjunction of luminance and relative location that often corresponds to object curvature and direction of lighting in naturalistic scenes. Experiment 1 showed that such search is influenced by several factors, including the type of gradient, the shape of the contour enclosing the gradient, and the background luminance. These factors were varied systematically in Experiment 2 in a three-dimensionality rating task and in a visual-search task. The factors combined interactively in the rating task, supporting the presence of an emergent property of three-dimensionality. In contrast, each factor contributed only additively to the speed of the visual-search task. This is inconsistent with the view that search is guided by specialized detectors for surface curvature or direction of lighting. Rather, it is in keeping with the view that search is governed by a number of "quick and dirty" processes that are implemented rapidly and in parallel across the visual field.

Attention↗
PubMed1990

Moon illusion in pictures: a multimechanism approach.

The existence of the moon illusion in pictorial representations was demonstrated in 6 experiments. Ss either judged the size of the moon in pictures, depicted as on the horizon or high in the sky, or drew horizon and elevated moons. The horizon moon was consistently judged to be larger than the elevated moon, independent of the angle at which the pictures are viewed. The distance paradox usually observed with the moon illusion (horizon moon apparently closer than the elevated moon) also exists in pictures. The magnitude of both size and distance effects depends on the salience of depicted depth cues. The pattern of results suggests that the moon illusion is caused by several interacting mechanisms and that use of pictorial stimuli may allow the separation of various cognitive from physiological contributions to the illusion.

Attention↗