Abstract
The issue of whether perceptual grouping can be formed without attention is important especially for object-based theories of attention. While support for both sides has been provided, it is commonly assumed that Gestalt principles of grouping are all processed at the same stage: Either all can be processed without attention, or all must be formed with the deployment of attention. Here we report evidence against such a unifying view. By adopting a sensitive measure concerning the relationship of grouping and attention designed by Moore and Egeth (1997), i.e., a measure of the Ponzo illusion when the background containing the two railroad tracks was unattended using the inattentional blindness paradigm (Mack and Rock, 1998), the formation of three grouping principles (color similarity, orientation similarity and collinearity) was examined. Results showed that grouping by color similarity and collinearity can be perceived to render the illusion under conditions of inattention, but this does not occur with grouping by orientation similarity. While color similarity can be grouped even with conflicting orientation information, grouping by collinearity fails with conflicting color information. These results provide evidence against the commonly held unifying view of various perceptual grouping principles, indicating that they are processed at different stages with respect to the deployment of attention.