The representation of feature associations

Dans le document The maintenance of cross-domain associations in working memory (Page 44-47)

WORKING MEMORY REPRESENTATIONS

1.1. The Multi-Component Model of Baddeley (and Hitch)

1.1.2. The representation of feature associations

The multi-component model as depicted in Figure 1.1 could have accommodated feature associations when all features belong to a same domain. However, no doubt existed on the fact that the representations of associated features belonging to different domains could not find their place in this model. Initially, the multi-component model had claimed that the central executive disposes of some maintenance capacity (Baddeley & Hitch, 1974). As described earlier, this option was however explicitly discarded in a later version of the model (Baddeley & Logie, 1999). Maintenance of associated features within the central executive would have corresponded perfectly with the integrative function that had been attributed to this component (Baddeley, 1986). And yet, this option was rendered impossible by excluding the maintenance function of the central executive. However, an elaboration of the multi-component model resolved the problem. In 2000, Baddeley integrated some kind of back-up maintenance store into the model, the episodic buffer. This episodic buffer was more or less conceived as a split off of the central executive, and in a certain way it replaced the storage capacity that was attributed to the central executive in the initial model. The episodic buffer was considered a limited-capacity maintenance system, capable of integrating information from different sources. It was conceptualized especially to account for several phenomena relying on the maintenance of associated features, but as well to offer a more solid account of rehearsal strategies. Among the observations the episodic buffer could offer a solution to, Baddeley (2000) mentioned first of all the fact that under articulatory suppression,

participants could still maintain a certain amount of visually presented digits. These were then clearly not maintained in the phonological loop, but how were they then maintained?

Secondly, it was observed that participants could maintain phrases consisting of more words than would be expected based on the span level for unrelated words. This clearly indicates that some other mechanisms than the sole maintenance of words comes into play when maintaining phrases. Apparently, syntactical information maintained in long term memory contributes to the maintenance of sentences, but in the initial multi-component model there was no place for such an interaction. Next to these implicit binding phenomena, there was also the need to account for explicit binding of features belonging to different domains. For example how to maintain a street name with its location on map? The multi-component model could not accommodate this kind of representations.

The episodic buffer was thus conceptualized to offer an explanation for these binding phenomena, but as mentioned before, to offer an explanation for phenomena observed

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concerning rehearsal as well. Baddeley (2000) mentioned for example the observation that children make use of some kind of rehearsal before the actual subvocal rehearsal strategy has developed. He suggested that a more general maintenance mechanisms could exist, consisting in the sequential allocation of attention to the material to be maintained. As the phonological loop is characterized by its phonemic encoding and subvocal rehearsal to achieve

maintenance, the attentional maintenance strategy would then act on a more general buffer that could maintain information from all kinds of domains. Baddeley stated even that this could then as well account for maintenance of information within the visuo-spatial sketchpad, for which a satisfying account of rehearsal had never really been reached. Once arrived at this point of reflection on rehearsal mechanisms, it might seem bizarre that the necessity of the existence of the visuo-spatial sketchpad was not reconsidered or further questioned. The replacement of the visuo-spatial sketchpad by a domain-general maintenance buffer might have offered the same degree of solutions as the inclusion of this new component. Anyhow, the multi-component model preferred to include the episodic buffer in order to fill some gaps within the framework of their working memory model.

The inclusion of the episodic buffer had thus been motivated on theoretical grounds.

However future research was necessary to delineate its characteristics. Two main assumptions about the episodic buffer could be submitted to validation quite easily (Baddeley, 2000). The first concerned the dependence of the episodic buffer on the attentional resources of the central executive to fulfill its main function, i.e. integrating information from different

sources. The second assumption concerned its separation from the domain-specific buffers. In order to mark this separation, the initial model doomed information from the domain-specific buffers to pass the central executive to reach the episodic buffer. A direct access was initially not envisaged (see Figure 1.2).

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Figure 1.2: Structure of the multi-component model after the introduction of the episodic buffer (Baddeley, 2000). © 2000 Elsevier

The research team behind the multi-component model, and hence behind the creation of the episodic buffer, started its investigations by examining the role of the central executive within the creation and maintenance of feature associations. This was done first of all on feature associations within the visuo-spatial domain (e.g., a green pencil, both features are visual in nature). This appears however quite counterintuitive as the episodic buffer was especially conceived to explain the existing associations between features belonging to

different domains. The rationale for starting research on within-domain associations has never explicitly been stated. Yet, earlier research on binding or the maintenance of bound

information had especially been performed on visuo-spatial feature associations. (e.g., Irwin, Zacks, & Brown, 1990; Luck & Vogel, 1997; Treisman, 1996). As such, investigating the creation and maintenance of visuo-spatial feature associations within a working memory context was not a complete step in the dark. Shortly after the first (disappointing) results on the binding and maintenance of visuo-spatial feature associations within the episodic buffer, research on within-domain binding was elaborated to feature associations within the verbal domain, mainly in the format of sentences. The research team remained as such faithful to the investigation of within-domain binding. Research on cross-domain binding (i.e., combining features from different domains) has then principally been executed by other researchers, not directly associated to the authors of the multi-component model. These researchers explored hence the multi-domain and multi-modal character of the episodic buffer, which was after all a main motivation for its creation. Research on cross-domain associations has then especially concentrated on the associations between verbal and spatial information, for example letters in locations.

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These two lines of research (on within and cross-domain associations respectively) will now in turn be discussed. Studies on within-domain associations had as their first concern the involvement of the attentional resources of the central executive. Studies on cross-domain associations have rather concentrated on the framework accounting for the accommodation of feature associations.

Dans le document The maintenance of cross-domain associations in working memory (Page 44-47)