Exploring the interaction between working memory and long-term memory: Evidence for the workspace model
van der Meulen, Marian
There is a large range of models of working memory, each with different scopes and emphases. Current interest focuses strongly on the interaction of working memory with long-term memory, as it has become clear that models of working memory alone are incapable of capturing some of our complex cognitive abilities. Most models have contrasting views on how this interaction is implemented. In this thesis, three classes of models are defined, each proposing a different type of interaction. The first model proposes that working memory acts as a gateway for perceptual input on its way to long-term memory. In the unitary model, working memory is seen as comprising the activated portion of long-term memory. The workspace model views working memory as a workspace that is separate from, and deals with the activated contents of long-term memory. The main aim of this thesis was to address the differences between these three models experimentally. Experiments 1 – 7 employed a dual-task paradigm to investigate the effects of irrelevant visual input on visuo-spatial working memory tasks. Two main findings emerged: (1) maintenance of images in working memory was largely insensitive to the effects of concurrent perceptual input; (2) mental imagery was susceptible to interference from irrelevant visual input. This interference effect was selective, as demonstrated by a lack of disruption of imagery by other secondary tasks. Experiment 8 further tested the three models by investigating implicit processing of visual information by neglect patients. It was found that implicit processing is mediated by the activation of long-term memory, in the absence of a conscious representation in working memory. These results together converge to support the workspace model, and suggest a view in which perceptual input activates the contents of long-term memory, prior to these activated representations being made available in a functionally separate working memory system for further processing. The gateway model and unitary model are unable to accommodate all findings. The implications of these results for existing theories about working memory are discussed.