Abstract
When and how do stimuli configure to produce a Gestalt? We propose that grouping may be equated with the creation of Emergent Features (EFs). Support has been previously shown for eight EFs in the context of Configural Superiority (CSE) and Inferiority (CIE) effects using an Odd-Quadrant discrimination task. The present study further tests EFs in a task of selective attention. Subjects rapidly classified stimuli composed of two elements, each of which was a straight line segment presented in one of 4 orientations: vertical, horizontal, positive diagonal, and negative diagonal. Stimuli differed on the orientation of one or both of the elements. Following Pomerantz and Garner (1973), we reasoned that when elements are perceptually organized so as to form a Gestalt, the ability to selectively attend to the orientation of any one element is impaired. Thus, if grouping, and the EFs it creates, are present, subjects should have difficulty attending to one element while ignoring variation in the other; i.e., they should show Garner Interference (GI). Our results confirmed that two-line configurations that yield CSEs also show GI, whereas configurations that don't yield CSE do not produce GI. Additionally, performance during a divided attention task, where subjects are required to pay attention to both elements simultaneously, was impaired for line pairs that did not configure but not for those that did, providing further converging evidence that grouping defines the units of selective attention.