MAINTENANCE OF CROSS-DOMAIN ASSOCIATIONS IN WORKING MEMORY
6.3. The validity of the processing tasks
The goal of Experiment 5 was to verify the adequacy of the verbal processing task we have used in Experiment 4. We combined the maintenance of verbal and cross-domain items with a verbal and a spatial processing task in a complex span design. If our semantic decision task creates indeed verbal interference over and above its attentional demand, then we should observe lower verbal span scores when combined with the semantic decision task than with the spatial fit task. For the cross-domain associations, we expected to find similar span scores in case of the verbal or spatial processing task, as we observed in Experiment 4.
Participants and Design
Forty-seven students of the University of Geneva were paid or given course credit for participation. They were randomly attributed to the verbal or cross-domain maintenance
condition. The domain of the processing task (verbal or spatial) was manipulated within subjects. Two participants did not reach the predetermined 80% accuracy criterion for both processing tasks during the training phase. The experiment was not continued for these participants, leaving us with 45 participants (mean age = 22.00, SD = 6.61, 42 female).
Materials and Procedure
Verbal and cross-domain memoranda were combined with the semantic decision task (verbal processing) and the spatial fit task (spatial processing) used in Experiment 4. Verbal maintenance items consisted of series of consonants ranging from two to seven. Letters were sequentially displayed on screen in a centrally displayed empty square. Six series of each length were created as in Experiment 1. Three of these were combined with the verbal processing task and three with the spatial processing task. A second version of this verbal maintenance condition was created to counterbalance this assignment. Series of two to seven cross-domain associations were created by assigning to each letter of the verbal maintenance condition a location out of the grid of 16 locations. A letter in location was then displayed as the letter in the assigned location highlighted in grey. As for the verbal maintenance
condition, two versions of this condition were created to counterbalance the assignment of the series to the two processing tasks.
The same procedure was used as in Experiment 4 with some minor exceptions. In this experiment, only the medium cognitive load condition was used in order to avoid unnecessary lengthening of the experiment. Instead of showing an indication of the cognitive load before each trial, participants were informed about the nature of the forthcoming processing task.
The semantic decision task was indicated by a picture of a polar bear and the spatial fit task by a square presenting two dots and a line. At the end of each trial, participants were informed about their score on the processing task. This feedback was given to motivate participants to keep their processing accuracy above 75 %.
Span scores were calculated according to the all-or-nothing unit scoring method. One third of a point was added for each series correctly recalled. A basis score of one was given as series of one memory item were omitted. A verbal and a cross-domain span score were
calculated in this way according to the maintenance condition, per processing task.
One participant in each maintenance condition did not reach the 75 % accuracy criterion for both processing tasks. The data of the remaining 43 participants were submitted to a 2 (Maintenance domain: verbal or cross-domain) X 2 (Processing task: verbal or spatial) repeated measure ANOVA with maintenance domain as between subject and processing task as within subject factor. The effect of maintenance domain was significant, F(1, 41) = 104.74, p < .001, η2 = .72, with verbal span scores (M = 4.94) exceeding cross-domain span scores (M = 2.34, see Figure 6.3). There was a significant effect of processing task, F(1, 41) = 20.03, p < .001, η2 = .33, with the verbal processing task resulting in lower span scores (M = 3.43) than the spatial processing task (M = 3.91), as well as a significant interaction, F(1, 41) = 18.68, p < .001. A further examination of this interaction revealed that combining verbal maintenance with a verbal processing task led to lower span scores than the combination with a spatial processing task, F(1, 41) = 39.62, p < .001, η2 = .49. This difference was not
observed for cross-domain maintenance, F(1, 41) < 1 and pBIC (H0|D) = .83.
Figure 6.3: Span scores as a function of maintenance domain and processing task in Experiment 5. Error bars represent standard errors.
Experiment 5 clearly showed that the verbal processing task had a more detrimental effect on verbal maintenance than the spatial processing task. This confirms the adequacy of the semantic decision task to create verbal interference. This effect was not observed for cross-domain maintenance and replicates thus the result obtained in Experiment 4. Based on the joint results of Experiment 4 and 5, we can conclude that verbal domain-specific resources
do not contribute to the maintenance of cross-domain associations. This is in contrast to our predictions.
In order to complete the design, we should continue to test the adequacy of the spatial processing task. However, Experiment 4 and 5 have already shown that a task capable of creating domain-specific verbal interference does not affect the maintenance of cross-domain associations. If any domain-specific interference was to be expected, then it was most
certainly verbal interference and not visuo-spatial. Domain-specific verbal interference has been shown in many occasions, while the existence of domain-specific visuo-spatial interference has often been questioned. The results of a control experiment testing the adequacy of the spatial fit task would not change the current conclusions. If we observe that the spatial fit task creates effectively spatial interference, we would have proven its adequacy but still hold on to the conclusion that the maintenance of cross-domain maintenance does not depend on visuo-spatial resources. If on the other hand we observe that the spatial fit task does not create spatial interference, this would rather confirm the doubts on the existence of visuo-spatial resources. In this case, it would be even less plausible that domain-specific visuo-spatial resources are involved in the maintenance of cross-domain associations. We have thus abandoned the control experiment testing the adequacy of the spatial fit task.
The results of Experiment 1, 3 and 4 have shown that domain-general attentional resources are implicated in the maintenance of cross-domain associations. They are however not involved any more than for the maintenance of single features. The involvement of domain-specific verbal or visuo-spatial resources was tested in the Experiments 4 and 5.
These showed no evidence for any implication of domain-specific resources in the
maintenance of cross-domain feature associations. To what extent do these results agree with the existing literature and what do they tell us over and above what we already know?
The implication of domain-general resources in the maintenance of feature
associations is no surprise. All studies adding an attention-demanding task to the maintenance of feature associations showed decreased memory performance (e.g., Allen et al., 2006; Allen et al., 2009; Brown & Brockmole, 2010; Fougnie & Marois, 2009; Karlsen et al., 2010;
Morey & Bieler, 2013; Vergauwe, Langerock, et al., 2014). Most of these studies also showed
that there was no differential impact of an attentional load on the maintenance of single features or feature associations. The studies from Brown and Brockmole (2010) and Fougnie and Marois (2009) are nevertheless exceptions to this observation.
All of these studies concern however the maintenance of visuo-spatial feature associations. Only one study investigated the attentional involvement in the maintenance of cross-domain feature associations. This concerns the study by Elsley and Parmentier (2009).
These authors concentrated mainly on the underlying representations for the maintenance of cross-domain associations and showed that attention had indeed an impact on the level of integration of these features. A reduction of the attentional resources led to an unintegrated maintenance of these cross-domain associations. In terms of memory performance, the insertion of an attention-demanding task resulted generally indeed in lower memory
performance. Further derivations from the presented results, in order to elucidate the impact of attentional resources on the maintenance capacity of cross-domain associations, would however go beyond the scope of the study of Elsley and Parmentier. Additional studies were hence required to be able to compare the involvement of attentional resources in the
maintenance of single features and cross-domain feature associations. This is what has been done in the Experiments 1 and 3. Both studies showed that attention did not have a different impact on the maintenance of cross-domain associations or single features. In Experiment 1, we could directly compare cross-domain feature associations with single features, as has been done in most studies in the visuo-spatial domain. In Experiment 3, we could compare the capacity limits between features that were presumed to be maintained integrated or isolated.
We observed that the attentional involvement for both types of maintenance was not different.
The results on the attentional involvement in the maintenance of cross-domain associations seem hence to adhere to the majority of studies on visuo-spatial feature associations, stating no particular involvement of attentional resources to maintain feature associations integrated.
The study of the involvement of domain-specific resources in the maintenance of visuo-spatial feature associations has largely been left aside. Cross-domain feature associations represent however the ideal instance of feature associations to explore the implication of both verbal and visuo-spatial domain-specific resources and several studies have hence investigated the reliance on these resources. The overall conclusion was that only verbal domain-specific resources would be implied. No evidence was found for the
involvement of domain-specific visuo-spatial resources in the maintenance of cross-domain
associations13. The results of our Experiments 4 and 5 did only partially confirm this conclusion. We did not find any evidence for either verbal or visuo-spatial domain-specific resources to be involved in the maintenance of cross-domain associations. This was not even the case when attentional resources were particularly low. As suggested before, these different results might be due to locus of the effect. The studies of Morey (2009) and Guérard et al.
(2013) both showed an involvement of verbal domain-specific resources in the maintenance of cross-domain associations. The experimental paradigm they used made however that in both studies domain-specific verbal resources were decreased already during the encoding of the feature associations. This was not the case in our Experiments 4 and 5. During the
encoding, no additional task or condition was inserted, creating hence an optimal context for participants to correctly encode the information. The goal of the present research project was after all to investigate the maintenance of cross-domain associations. This different
methodology might hence explain the observed discrepancies about the involvement of domain-specific verbal resources. Experiment 4 was nevertheless in agreement with the few studies investigating the role of visuo-spatial domain-specific resources. These studies neglected the implication of visuo-spatial resources in the maintenance of cross-domain associations.
Despite the overall contradictory results observed between the studies of Morey (2009) and Guérard et al. (2013) and ours, there was nevertheless some kind of convergence.
The study of Morey and Guérard et al. both showed that binding information protected this information from within-domain interference. For example, the study from Morey showed that verbal features were less affected by articulatory suppression when these were maintained integrated with spatial features then maintained as single features. Apparently, the
involvement of domain-specific resources diminishes thus in case of integrated maintenance.
Our results go even further and suggest no involvement of domain-specific resources. We will further elaborate on the involvement of domain-specific resources in the General discussion, once we have taken into consideration the underlying representations for the maintenance of cross-domain associations.
13 Only one study showed visuo-spatial resources to be involved in cross-domain feature associations, but its implication was only demonstrated at encoding (Allen, et al., In press).