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 and 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 and 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.

Two types of serial dependence in visual working memory

“…If recently memorized information can bias current processing, then serial dependence might operate regardless of whether stimuli are serially presented across trials or within a trial. Accordingly, Huang and Sekuler () found that the spatial frequency of a Gabor stimulus was attracted towards the spatial frequency of a previously presented Gabor also when both stimuli were encoded within a trial (see also Dubé, Zhou, Kahana, & Sekuler, ). Strikingly, two recent studies found a repulsive instead of attractive bias, thus pointing at a different mechanism of serial dependence.…”

Attention-modulated Alpha-band Oscillations Protect against Intrusion of Irrelevant Information

“…In this way, subjects’ reproductions of the spatial frequency of the remembered stimulus yield a sensitive, trial-by-trial continuous measure of accuracy. This information-rich measure of accuracy made it possible not only to gauge whether there was an error in memory, but more importantly to gauge the degree to which errors reflected the influence of the task-irrelevant stimulus (Dube, Zhou, & Sekuler, under review; Huang & Sekuler, 2010b). Many factors during each trial may contribute to the total error including pure error of reproduction, but, as explained below, the use of Gabor stimuli and the recall technique made it possible to disentangle the influence of other stimuli seen during the experiment, particularly each trial’s nonTarget stimulus.…”

Memory strength versus memory variability in visual change detection

“…When the observer is tested regarding the identity of an object from a given spatial position, there may be some probability that the observer makes the judgment with respect to an item from the wrong position (e.g., Bays et al, 2009;Donkin, Tran, & Pelley, 2015;Dubé, Zhou, Kahana, & Sekuler, 2014). One approach to addressing this issue is to conduct paradigms in which the observer is presented with only a single object from a single spatial position on each trial.…”