The default maintenance strategy for cross-domain associations
The ensemble of our results seems thus to suggest that cross-domain associations are maintained integrated. In view of the literature on the maintenance of cross-domain
associations, maybe we should rather state that cross-domain associations “can” thus be maintained integrated, as apparently this is not always the case. Within the design we used to test our hypothesis, series of cross-domain associations consisted of sequentially presented objects composed of a letter in a location. The span procedure required participants to recall all objects in correct order. This means each letter in its correct serial position and each location in its correct serial position. Participants apparently maintained the cross-domain objects and recalled them as such. They could however also have maintained a series of letters and a series of locations separately. At the moment of recall, the serial position would then serve as the link to recompose the objects. Cowan, Saults, and Morey (2006) showed that this
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latter maintenance strategy was the default strategy used by adults. In this study, participants had to maintain the association between the location of houses and the name of their resident (see Figure 8.1). A repetition of houses (i.e., using a same house several times in one series for different residents) increased the difficulty of the spatial path and the use of the spatial code should hence result in a lower performance on the association task. This is indeed what was observed. The use of articulatory suppression during the association task inversed this pattern. Articulatory suppression discourages the use of a verbal code (and hence the
simultaneous use of the verbal and spatial code in this task). It was indeed observed that under articulatory suppression, the repetition of houses within a sequence did no longer result in reduced performance. According to Cowan et al. (2006), adults make thus by default use of a simultaneous verbal and spatial code to maintain cross-domain associations, instead of a more abstract cross-domain code. The circumstances can however inverse the use of strategies.
Figure 8.1: Example of the association task used by Cowan et al. (2006). © 2006 Elsevier
The results of our experiments did not seem to adhere to this conclusion that cross-domain associations are maintained by default as verbal and spatial codes. This was most explicitly demonstrated by the recognition paradigm used in Experiment 8. These results strongly suggested that the integrated letter-location presentation resulted in an integrated feature representation in working memory. It might however be argued that despite the existence of such a representation, participants would principally make use of a verbal and spatial code to maintain cross-domain associations. This argument is contested by the results of Experiment 4. In this experiment, cross-domain maintenance was combined with a neutral, a verbal and a spatial processing task. If recall of the cross-domain associations relied on a verbal and a spatial code, then the verbal and spatial processing task should have resulted in interference and hence lower cross-domain memory performance. This was not the case.
Could it be argued that attentional resources take over when verbal or spatial resources are insufficient? The study by Cowan et al. (2006) partly suggests such a mechanism. In their
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task of associating names with houses, increasing the difficulty of the spatial component of the task resulted in lower association performance. From this result, the authors assumed participants to make use of a spatial code, combined with a verbal code. However, when articulatory suppression was used during the association task, there was no longer an effect of visual path difficulty. This result suggests hence that when verbal resources are insufficient, this induces a strategy change to the use of an abstract code. When spatial resources were insufficient to perform the task, no such a strategy change was however observed15. Our results do however not support this strategy switch in case of insufficient domain-specific resources. If this were the case, then the results of Experiment 4 (combining cross-domain associations with neutral, verbal and spatial processing) should have resulted in an interaction between the domain and the cognitive load of the processing task anyhow. The default use of a verbal and spatial code to maintain the cross-domain association might have been obscured in the low cognitive load by attentional resources taking over from the domain-specific resources. Under a high cognitive load, both domain-specific and domain-general attentional resources are low. This should thus anyway result in lower performance in case of the verbal or spatial processing task, in comparison with the neutral processing task which would still allow the simultaneous use of the verbal and spatial codes. To conclude, several of our
experiments offered convergent evidence that participants did use a domain-general integrated maintenance strategy as the default strategy to maintain cross-domain associations.
A possible explanation for this difference in default maintenance strategy between our and Cowan et al.’s (2006) experiments might be the output procedure. In our experiments, participants had to recall the cross-domain maintenance in its entirety, and the association appeared on screen as an object both at study and at recall. In Cowan et al.’s experiment, participants saw at test all the houses on screen and one residents name in the middle (see Figure 8.1). This indication of the possibility of fractioning the association in features might have influenced the maintenance strategy. A recent study on the maintenance of within-domain feature associations (Vergauwe & Cowan, In press) has shown that the testing situation has a strong impact on the units used for retrieval. These authors showed integrated feature associations at study and tried to manipulate the maintenance mode. In one condition, they encouraged for example object-based maintenance by making the maintenance of object
15 If we assume visuo-spatial resources not to exist, but to consist of attentional resources employed for a visuo-spatial task, then it would make sense that no change in strategy is occurring. The difference in strategy would then consist in either the maintenance of verbal features through a verbal resource and in parallel the spatial features through an attentional resource, or the maintenance of the verbal and spatial feature together by use of the attentional resource.
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information necessary for a correct performance of the task. Despite this recommendation and object representations apparently being available, a testing situation proposing a simultaneous side by side presentation of the two possible constituent features disfavored objects and favored features as the maintenance units, in comparison with the presentation of objects at test which favored objects at the maintenance units. The procedure used by Cowan et al.
(2006) for the house association task might hence have favored features as the maintenance units.
The recent study by Allen et al. (In press) on visuo-spatial bootstrapping provided moreover counterevidence for this reassociation procedure of verbal and spatial items at recall to be the default procedure. We have mentioned before the study by Darling and Havelka (2010) that showed that digit recall benefited from the presentation of these digits on a telephone keypad, as compared to the presentation on a horizontal number line or isolated digit presentation. A further investigation of this phenomenon (Allen et al., In press) had shown that spatial tapping during recall did not have any influence on the bootstrapping effect, while spatial tapping during encoding neutralized the effect. As spatial tapping did not have any effect when performed at recall, this disfavors the hypothesis that verbal and spatial information are maintained separately and only associated at recall. If this were the case, spatial tapping at recall should have reduced access to the representation of the visuo-spatial sketchpad and as such neutralized the bootstrapping effect.
The evidence from our studies favoring object-based maintenance of cross-domain associations is in line with the majority of studies investigating the underlying representations for cross-domain associations. Indications of object-based maintenance have been shown both in intentional as well as incidental binding situations (e.g., Darling & Havelka, 2010; Elsley &
Parmentier, 2009; Morey, 2009, 2011). The difference between these kind of bindings is however not always that obvious. If there is no incentive to maintain the binding, its
maintenance is assumed incidental. For example in the study of Elsley and Parmentier (2009), participants did not need to maintain the links between the features in order to decide at test whether both the letter and the location had been shown at study, independently of their association. Questioning participants at test about the link between the features modifies however the nature of the task into an intentional binding task. Considering our own design, we have the feeling of falling somewhere in between. Strictly speaking, there is no need to maintain the binding. The use of a verbal and spatial code along with the serial positions allows one to correctly perform the task. Nevertheless, our results indicated that participants
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in the integrated presentation condition did maintain the link and this might have been
intentional as the recall procedure in the integrated presentation condition incited object-based recall. The results we have presented in this project do not allow us to decide on the
intentionality of this binding process. Anyhow, both incidental and intentional binding have been shown in the literature to result in integrated maintenance of cross-domain associations and our results do hence provide support to this kind of maintenance. In the next section, we will further elaborate on the topic of intentionality and on the possibility of different levels of integration.