Object-based selection: The role of attentional shifts

Dominique Lamy*, Howard Egeth

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

98 Scopus citations


The objective of this paper was to investigate under what conditions object-based effects are observed. Recently, Watson and Kramer (1999) used a divided-attention task and showed that unless top-down factors induce a bias toward selection at a higher level, object-based effects are obtained when same-object targets belong to the same uniformly connected (single-UC) region, but not when they belong to different single-UC regions grouped into a higher order object (grouped-UC regions). We refine this claim by proposing that a critical factor in determining whether or not object-based effects with grouped-UC regions are observed is the need to shift attention. The results of four experiments support this hypothesis. Stimuli and displays were similar to those used by Egly, Driver, and Rafal (1994). Subjects had to make size judgments. Using different paradigms, we obtained object-based effects when the task required shifts of attention (spatial cuing, same vs. different judgment with asynchronous target onsets), but not when attention remained either broadly distributed (same vs. different judgment with simultaneous targets) or tightly focused (response competition paradigm).

Original languageEnglish
Pages (from-to)52-66
Number of pages15
JournalPerception and Psychophysics
Issue number1
StatePublished - Jan 2002


FundersFunder number
National Institute of Mental HealthR01MH057388


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