Perceptual grouping via spatial selection in a focused-attention task

Theories of attention can be separated into those that select by location, and those that select by location-invariant representation. Experiments demonstrating stronger interference or facilitation from distracters grouped by nonspatial features with the target than ungrouped distracters have been considered as evidence for the selection of location-invariant representations. However, few studies have measured spatial attention directly at the locations of the grouped or ungrouped objects. In these experiments subjects responded to spatial probes (dots) while also identifying a cued target letter among distracters. Probe responses were faster for distracter locations with the target color than for those with the nontarget color, implying that target-color locations receive more attention. This pattern of spatial attention may explain why target-color distracters interfere more with target identification than nontarget-color distracters. These results suggest that although attention can be directed by nonspatial properties such as grouping by color or organization of the scene into objects, selection may ultimately be based on location. (C) 2001 Elsevier Science Ltd. All rights reserved.