Abstract

For certain texture pairs, the ease of perceptual segregation changes when the roles of targets and distractors are switched. For example, it is far more difficult to detect an array of circles in a field of ellipses than vice versa. Similarly, it is more difficult to detect an array of straight lines in a field of curved lines than the reverse. The existence of such perceptual asymmetries suggests that the element that is easier to detect (i.e., an ellipse or curve) contains an emergent feature. To further determine the significance of these asymmetries, we studied discrimination with short presentations (40 ms duration) of only two elements: (1) one target and one distractoror (2) two distractors. False-alarm rates for two distractors were much higher if the presentations were composed of the more easily detected element pairs. These results suggest that these elements are not reliably perceived and that their duals are more stable. We therefore conclude that asymmetry is not the result of an emergent attribute. Rather, elements may not be completely resolved because of either short presentation or, in the case of displays composed of many elements (i.e., textures), because of lateral inhibition owing to the limited spatial extent of focal attention.

© 1990 Optical Society of America