Working memory storage is intrinsically domain specific.

Abstract

A longstanding debate in working memory (WM) is whether information is maintained in a central, capacity-limited storage system or whether there are domain-specific stores for different modalities. This question is typically addressed by determining whether concurrent storage of 2 different memory arrays produces interference. Prior studies using this approach have shown at least some cost to maintaining 2 memory arrays that differed in perceptual modalities. However, it is not clear whether these WM costs resulted from competition for a central, capacity-limited store or from other potential sources of dual-task interference, such as task preparation and coordination, overlap in representational content (e.g., object vs. space based), or cognitive strategies (e.g., verbalization, chunking of the stimulus material in a higher order structure). In the present study we assess dual-task costs during the concurrent performance of a visuospatial WM task and an auditory object WM task when such sources of interference are minimized. The results show that performance of these 2 WM tasks are independent from each another, even at high WM load. Only when we introduced a common representational format (spatial information) to both WM tasks did dual-task performance begin to suffer. These results are inconsistent with the notion of a domain-independent storage system, and suggest instead that WM is constrained by multiple domain-specific stores and central executive processes. Evidently, there is nothing intrinsic about the functional architecture of the human mind that prevents it from storing 2 distinct representations in WM, as long as these representations do not overlap in any functional domain.

Central attention is serial, but midlevel and peripheral attention are parallel—A hypothesis

“…We emphasize that while each sensory system has such preferred representational formats, it is possible for a sensory system to feed into other representational formats as well (see bold versus light lines at the bottom levels of Figure 1). This non-orthogonal relationship between sensory systems and representational formats has frequently posed challenges in interpreting experimental results (e.g., Fougnie, Zughni, Godwin, & Marois, 2015; Saults & Cowan, 2007). The distinction between representational formats and sensory systems is important because we suggest that attention functions in parallel across representational formats, not sensory systems per se 3 .…”

“…In order to assess our hypothesis that central attention is serial but mid-level and peripheral attention are parallel across representational formats, we focus our discussion to studies in which the two tasks relied on distinct representational formats. Most often, this is accomplished by presenting tasks in distinct perceptual modalities as well, though we suggest that it is at least theoretically possible to accomplish this using two tasks in the same perceptual modality but relying on distinct representational formats, and it is important to reiterate that presenting tasks in distinct modalities does not automatically entail the use of distinct representational formats (Fougnie et al, 2015). …”

“…Saults and Cowan (2007) viewed this as evidence for a central working memory store, though we would suggest that the results do not distinguish between central storage and processing. At any rate, when tasks in a similar paradigm were chosen to depend on completely distinct storage formats (visual spatial versus auditory object feature formats) and there were longer delays between encoding of the two working memory loads, there no longer was interference (Fougnie et al, 2015). Instead, Fougnie et al (2015) provided evidence supporting the view that multiple attentional loci may be maintained at middle and peripheral levels of the hierarchy, if we can rely on the view that non-central attention is required for working memory maintenance.…”

“…At any rate, when tasks in a similar paradigm were chosen to depend on completely distinct storage formats (visual spatial versus auditory object feature formats) and there were longer delays between encoding of the two working memory loads, there no longer was interference (Fougnie et al, 2015). Instead, Fougnie et al (2015) provided evidence supporting the view that multiple attentional loci may be maintained at middle and peripheral levels of the hierarchy, if we can rely on the view that non-central attention is required for working memory maintenance. Specifically, Fougnie et al (2015) used a Bayesian meta-analysis of their seven experiments to demonstrate almost ten times as much evidence against cross-format interference in working memory capacity as in favor of such interference.…”

Short-term memory stores organized by information domain

“…Visual and auditory STM are influenced by many of the same factors, such as serial position, retention interval, and load (Visscher et al, 2007). STM capacity for mixed auditory and visual arrays is larger than capacity for either visual or auditory, but smaller than their sum, suggesting that some portion of STM capacity is shared between modalities (Saults & Cowan, 2007; Fougnie, Zughni, Godwin, & Marois, 2014). …”