Effects of contrast on spatial and temporal integration in 2D shape perception from dynamic occlusion

Abstract

In self-motion, research has shown that optic flow can be a source that supplies essential information about heading, speed, and characteristics of the surrounding environment. Evidence has shown that increases in optic flow quality and quantity have additive effects on steering performance. Further, studies have shown that spatial integration (e.g., stimuli density) and temporal integration (e.g., stimuli lifetime) may play a key role in motion perception. In the current study, we examined how spatial and temporal integration are affected by the quality of optic flow in generating 2-D shape perception. Participants were asked to identify a 2D shape resulting from kinetic occlusion information. Displays consisted of 2D arrays of dots forming both foreground objects and the background texture. When the foreground object moves the disappearance and reappearance of back ground dots can be used to recover the object shape. Three experiments were conducted in which optic flow density, display contrast, and optic flow lifetime were variables of interest. In each of the three experiments, the threshold of one variable was measured, using a four-alternative forced choice staircase, while the other two variables were manipulated. In experiment 1, optical flow density threshold was measured for 8 participants using a 2 (contrast) by 2 (lifetime) within-subjects design; in experiment 2, contrast threshold was measured for 5 participants using a 3 (density) by 3 (lifetime) within-subjects design; in experiment 3, lifetime threshold was measured for 5 participants using a 3 (density) by 3 (contrast) within-subjects design. The results showed the performance in 2D shape perception decreased as a function of decreased contrast, decreased lifetime, and decreased density. These results suggest the spatial and temporal integration might be potential predictors of driving performance under low contrast conditions. Meeting abstract presented at VSS 2012