Active regulation of altitude as a function of optical texture.

Two empirical studies are reported that examine active regulation of altitude as a function of the type of ground texture. Three ground textures were examined: lines perpendicular to the direction of motion, lines parallel to the direction of motion, and the combination (i.e., square or checkerboard texture). Although subjects only controlled altitude, disturbances were introduced on three axes: vertical, lateral, and fore-aft. The results show a clear advantage for texture parallel to the direction of motion. However, in considering these results in the context of previous research on altitude control, the argument is made that there is no compelling evidence that suggests either parallel (splay) or perpendicular (density) texture is privileged with regard to altitude control. Rather, the most effective display for altitude control will be the one that best isolates the optical activity associated with changing altitude from the optical activity arising from other sources of disturbance (such as forward locomotion). Such a display will make it easier for the observer to distinguish and respond specifically to the disturbances of altitude.     

Variations in size judgements as a function of surface texture

Adult subjects made monocular size judgements in two experiments in which the independent variables of surface texture and restrictions on viewing conditions were manipulated. Texture density gradients of stimulation had a significant influence of size judgements only under the less reduced conditions of observation when subjects could see other textured surfaces beyond the surfaces over which judgements were made. Identical manipulations of surface texture had earlier been found to have a highly significant influence on relative distance judgements (Newman, 1971). The principally negative results were thus taken to imply that subjects extract different information from the texture density gradient when judging size from that extracted when judging relative distance.     

Simulation of curved surfaces from patterns of optical texture

Previous research on the perceptual analysis of optical texture has been severely restricted by the lack of an appropriate technique for distributing texture on curved surfaces in a uniform manner. In an effort to overcome this problem, the present article presents a new algorithm for generating stochastically regular distributions of texture on any smooth surface regardless of its curvature. We also present a new technique for representing the global organization of a textured image based on the formal concept of a projected area field.     

Perception of three-dimensional form from patterns of optical texture

The research described in the present article was designed to investigate how patterns of optical texture provide information about the three-dimensional structure of objects in space. Four experiments were performed in which observers were asked to judge the perceived depth of simulated ellipsoid surfaces under a variety of experimental conditions. The results revealed that judged depth increases linearly with simulated depth although the slope of this relation varies significantly among different types of texture patterns. Random variations in the sizes and shapes of individual surface elements have no detectable effect on observers' judgments. The perception of three-dimensional form is quite strong for surfaces displayed under parallel projection, but the amount of apparent depth is slightly less than for identical surfaces displayed under polar projection. Finally, the perceived depth of a surface is eliminated if the optical elements in a display are not sufficiently elongated or if they are not approximately aligned with one another. A theoretical explanation of these findings is proposed based on the neural network analysis of Grossberg and Mingolla.     

Executive function as a function of sub-clinical psychopathy

Some aspects of executive function are thought to be dysfunctional in psychopathic individuals. We administered a small battery of neuropsychological tests (spatial alternation task, object alternation task, and Porteus Maze) to two samples of college students and obtained a measure of psychopathy via a self-report questionnaire. Psychopathic traits were related to the tests of object alternation and Porteus Maze but not to the spatial alternation task. Our results support the hypothesis of orbitofrontal cortex (OFC) dysfunction with sparing of dorsolateral prefrontal cortex (DLPFC) in psychopathy and provide a downward extension of this theory to sub-clinical levels of psychopathy.     

Kinetic disruption of optical texture: The perception of depth at an edge

An examination of the changes in visual stimulation that result from changes in the occlusion of one surface or object by another suggests two hypotheses about the motion-carried information that is sufficient for the perception of the relative depth at an edge as well as the perception of occlusion. Ss’ reports when shown displays containing only this information give strong support to the hypotheses.     

Conservatism as a function of bag composition

The first purpose of this bookbag and pokerchip experiment was to examine the influence of the sample size and the relative frequency of the red chips in the sample on the amount of conservatism. The second purpose was to replicate the results of DE SWART (1972), and to test his hypothesis that the slope B of the function: log Φ(T)=A+B(r−b), is linearly related to log [p_r/(1−p_r)], where p_r represents the bag composition.     

Perceived duration as a function of pitch

It was demonstrated with 7 observers that the duration of a high frequency tone was perceived to be longer than the duration of a low frequency tone, even though the actual duration of the two tones was equal.     

Social categorization as a function of priming

The present study investigates the effect of priming on the use of social categorizations. Using sex and race as stimulus categorizations, previous studies failed to confirm the hypothesis that priming one of the two available categorizations would enhance the use of the primed categorization relation to the not-primed categorization. As suggested by Stangor, Lynch, Duan and Glass (1992). a momentary increase in accessibility may be insufficient to further enhance the use of highly accessible categorizations like race and sex, but it may be expected that priming will increase the use of categorizations which are less habitually used in daily life. The results of the present experiment support the hypothesis that, when the stimulus categorizations are weakly accessible (university major, university town), the relative use of the previously primed categorizations does indeed increase, compared to the alternative, not-primed, categorization.