Measuring spatial attention during task-irrelevant perceptual grouping

M. S. Kim, K. R. Cave

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Abstract

Purpose. When subjects categorize a target letter appearing at a known location, interference from distractor letters is greater when they share features (e.g., common color or motion) with the target and thus are easily grouped with the target. This grouping effect has been interpreted as evidence against location-based visual selection (spatial attention). We investigated the relationship between perceptual grouping by color and spatial attention. Methods. Subjects reported the target letter appearing at a known location flanked by distractor letters. Some distractors shared the same color as the target and some did not. On some trials, a spatial probe (a small black dot) appeared in a position formerly occupied by one of the letters. The response times to the probe were used to measure spatial attention at the probed locations. To determine whether there was a different time course for spatial attention, we used two different time delays from the onset of the letter array to the onset of the probe: 60 msec and 150 msec SOA's. Results. Probe RTs were compared for two flanking distractors adjacent to the target, one with the target color and one with the nontarget color. For the early SOA, probe responses were faster at the location of the distractor with the nontarget color, while for the later SOA, responses were faster at the location of the target color. Conclusions. The results imply that at first attention is drawn to the location of the distractor with the nontarget color, but that soon thereafter the distractor location with the target color receives more attention. This spatial attention to distractor locations with the target color may explain why they interfere more with target identification than distractors with a nontarget color.

Original languageEnglish
Pages (from-to)S528
JournalInvestigative Ophthalmology and Visual Science
Volume37
Issue number3
Publication statusPublished - 1996 Feb 15

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All Science Journal Classification (ASJC) codes

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

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