Academic journal article Memory & Cognition

Interference between Storage and Processing in Working Memory: Feature Overwriting, Not Similarity-Based Competition

Academic journal article Memory & Cognition

Interference between Storage and Processing in Working Memory: Feature Overwriting, Not Similarity-Based Competition

Article excerpt

Eight experiments with the complex span paradigm are presented to investigate why concurrent processing disrupts short-term retention. Increasing the pace of the processing task led to worse recall, supporting the hypothesis that the processing task distracts attention from maintenance operations. Neither phonological nor semantic similarity between memory items and processing-task material impaired memory. In contrast, the degree of phonological overlap between memory items and processing-task material affected recall negatively, supporting feature overwriting as one source of interference in the complex span paradigm. When compared directly, phonological overlap impaired memory, but similarity had a beneficial effect. These findings rule out response competition or confusion as a mechanism of interference between storage and processing.

One popular characterization of working memory is as a system for the simultaneous short-term storage and processing of information. This notion is reflected in many paradigms used to study working memory, such as the complex span paradigm, in which encoding of memory items for immediate recall alternates with brief periods of processing additional, not-to-be-remembered material. For instance, in the operation span task, participants alternate between encoding a letter for recall and evaluating arithmetic equations (Turner & Engle, 1989). In the reading span task, they alternate between reading a sentence and encoding the sentence's last word for recall (Daneman & Carpenter, 1980).

Adding concurrent processing to a short-term memory task has two consequences. First, memory performance is much reduced relative to comparable memory tasks without processing demand (so-called simple-span tasks). Second, combinations of memory and processing, as in complex span, are better predictors than simple span for performance on complex cognitive tasks (Ackerman, Beier, & Boyle, 2005; Daneman & Merikle, 1996; but see Colom, Rebollo, Abad, & Shih, 2006). Why does concurrent processing impair short-term storage? Answering this question would be an important step toward understanding why working memory capacity is limited and why it is related to complex cognition.

One answer is that the processing task delays recall while preventing rehearsal, so that memory traces decay over time (Barrouillet, Bernardin, & Camos, 2004; Towse, Hitch, & Hutton, 2000). Decay cannot be the only factor, however, because memory impairment is larger when memory items and the material of the processing task come from the same category (words vs. numbers) than when they come from different categories (Conlin, Gathercole, & Adams, 2005; Li, 1999). These findings point to a contribution from similarity-based interference between memory contents and the materials involved in the processing task. Saito and Miyake (2004), using the reading span task, varied processing time and the amount of material processed (i.e., length of sentences to be read) independently. They found that only the amount of material affected memory and argued that interference between memory items and representations involved in the processing task, rather than decay, impairs complex span performance. Oberauer and Lewandowsky (2008) fit competing models to data from a variant of the complex span paradigm and found that an interference-based model provided a better fit than a decay-based model did.

The present research seeks further evidence on the role of interference between memory contents and concurrently processed material, and aims at distinguishing four mechanisms by which processing could impair memory. The first mechanism is distraction of attention. The processing demand is assumed to distract a general attentional mechanism-sometimes referred to as a bottleneck- from the memory items, thereby preventing their maintenance or further consolidation in memory (Barrouillet et al., 2004; Hudjetz & Oberauer, 2007). …

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