Academic journal article Attention, Perception and Psychophysics

Working Memory Resources Are Shared across Sensory Modalities

Academic journal article Attention, Perception and Psychophysics

Working Memory Resources Are Shared across Sensory Modalities

Article excerpt

Published online: 17 June 2014

# The Psychonomic Society, Inc. 2014

Abstract A common assumption in the working memory literature is that the visual and auditory modalities have separate and independent memory stores. Recent evidence on visual working memory has suggested that resources are shared between representations, and that the precision of representations sets the limit for memory performance. We tested whether memory resources are also shared across sensory modalities. Memory precision for two visual (spatial frequency and orientation) and two auditory (pitch and tone duration) features was measured separately for each feature and for all possible feature combinations. Thus, only the memory load was varied, from one to four features, while keeping the stimuli similar. In Experiment 1, two gratings and two tones-both containing two varying features-were presented simultaneously. In Experiment 2, two gratings and two tones-each containing only one varying feature-were presented sequentially. The memory precision (delayed discrimination threshold) for a single feature was close to the perceptual threshold. However, as the number of features to be remembered was increased, the discrimination thresholds increased more than twofold. Importantly, the decrease in memory precision did not depend on the modality of the other feature(s), or on whether the features were in the same or in separate objects. Hence, simultaneously storing one visual and one auditory feature had an effect on memory precision equal to those of simultaneously storing two visual or two auditory features. The results show that working memory is limited by the precision of the stored representations, and that working memory can be described as a resource pool that is shared across modalities.

Keywords Working memory . Attention . Load . Precision . Psychophysics . Discrimination threshold . Audio-visual . Auditory features . Visual features . Cross-modal

The origin of memory limitations has been a major issue of debate in working memory research. The classical model of working memory suggests that both the visual and auditory modalities have separate and independent stores of limited capacity for short-term maintenance (Baddeley, 2010; Baddeley & Hitch, 1974). The two subsystems, as well as other aspects of working memory, have been studied using a concurrent-task procedure in which participants perform two tasks simultaneously during memory encoding-for example, a digit span task and a reasoning task (Baddeley & Hitch, 1974). In such settings, the recall of verbal materials is more disrupted by a phonological task than by a nonphonological visual task, and the recall of visual materials is disrupted more by a spatial task than by a verbal task (Brooks, 1968). Fur- thermore, when the participant is instructed to continuously shadow (i.e., repeat aloud) spoken letters during memory encoding, this verbal task disrupts delayed recall of simulta- neously heard verbal materials more than delayed recall of simultaneously seen visual material (Kroll, Parks, Parkinson, Bieber, & Johnson, 1970). In addition, a spatial task involving letters disrupts spatial tracking but not performance in a verbal task (Baddeley, 1986), and visual memory is less disturbed than auditory memory while simultaneously performing a backward-counting task (Scarborough, 1972). These results suggest separate working memory subsystems for visuospatial and verbal/phonological materials. However, the subsystems are not totally independent, since both are controlled by cen- tral executive functions, which explain subtle interference effects. An alternative to separate auditory and visual memory stores is that the limitation arises from some general mecha- nism or process with a limited capacity, regardless of the sensory modality-for example, from a limited focus of at- tention (Cowan, 1997, 2011). According to this view, working memory is a part of long-term memory that is activated by the focus of attention (Cowan, 1997, 2011). …

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