title: Similarity-based distortion of visual short-term memory is due to perceptual averaging.
abstract: A task-irrelevant stimulus can distort recall from visual short-term memory (VSTM). Specifically, reproduction of a task-relevant memory item is biased in the direction of the irrelevant memory item (Huang & Sekuler, 2010a). The present study addresses the hypothesis that such effects reflect the influence of neural averaging under conditions of uncertainty about the contents of VSTM (Alvarez, 2011; Ball & Sekuler, 1980). We manipulated subjects' attention to relevant and irrelevant study items whose similarity relationships were held constant, while varying how similar the study items were to a subsequent recognition probe. On each trial, subjects were shown one or two Gabor patches, followed by the probe; their task was to indicate whether the probe matched one of the study items. A brief cue told subjects which Gabor, first or second, would serve as that trial's target item. Critically, this cue appeared either before, between, or after the study items. A distributional analysis of the resulting mnemometric functions showed an inflation in probability density in the region spanning the spatial frequency of the average of the two memory items. This effect, due to an elevation in false alarms to probes matching the perceptual average, was diminished when cues were presented before both study items. These results suggest that (a) perceptual averages are computed obligatorily and (b) perceptual averages are relied upon to a greater extent when item representations are weakened. Implications of these results for theories of VSTM are discussed.
authors.affiliation: University of South Florida, 4202 East Fowler Ave., Tampa, FL 33620, USA. Electronic address: chaddube@usf.edu.
authors.forename: Chad
authors.initials: C
authors.lastname: Dubé
authors.affiliation: Weaver, Austin, Velleneuve, and Sampson, LLP, 555 12th St., Oakland, CA 94607, USA.
authors.forename: Feng
authors.initials: F
authors.lastname: Zhou
authors.affiliation: University of Pennsylvania, 3401 Walnut St., Philadelphia, PA 19104, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Kahana
authors.affiliation: Brandeis University, 415 South Street, Waltham, MA 02454, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Sekuler
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology*; D003463:Cues; D005260:Female; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D021641:Recognition, Psychology; D014796:Visual Perception / Q000502:physiology*
keywords: Distributional analysis; Perceptual averaging; Recognition memory; Selective attention; Visual short-term memory