Representations derived from the recognition paradigm

Dans le document The maintenance of cross-domain associations in working memory (Page 174-189)

REPRESENTATIONS OF CROSS-DOMAIN ASSOCIATIONS IN WORKING MEMORY

7.3. Representations derived from the recognition paradigm

Experiment 8

Experiment 8 combined a recognition and a recall paradigm. The recognition paradigm allowed determining the nature of the underlying representations. We used the classical recognition paradigm as used by Prabhakaran et al. (2000) and many others that we explained in chapter one. The test probe consisted always of a letter in a location. Participants were asked to indicate whether they had seen both the letter and the location at study,

independently of their association. The critical comparison to infer the presence of an

integrated feature representation consisted in the comparison of exact and recombined probes.

Faster and more accurate responses to exact probes point to integrated maintenance, as these integrated representations can be compared directly to the probe. In case of a recombined probe, the integrated representations of the memory items have to be disassembled and reorganized to allow for comparison. These processes take time and could allow the intrusion of errors.

The recall paradigm was the same as used in Experiments 3, 6 and 7. It was inserted next to the recognition paradigm first of all to verify that the introduction of the recognition paradigm did not lead to any changes in the recall performance. Secondly, the use of this double paradigm should result in direct conclusions about the relationship between maintenance mode (object-based or feature-based) and recall performance. In the present experiment, feature presentation time was kept constant at 1500 ms in the integrated and isolated presentation condition. We expected as in experiment 6 and 7 to observe equal span scores in the integrated and the isolated presentation conditions. Based on previous studies using this recognition paradigm to test the underlying representations of cross-domain associations (e.g., Elsley & Parmentier, 2009; Morey, 2011; Prabhakaran et al., 2000), we expected the integrated presentation to result in integrated object-based maintenance. We did not expect the isolated presentation to result in this kind of object-based maintenance. We also manipulated the cognitive load of the processing task. This manipulation was applied both in the recall and the recognition trials. In the previous experiments, we have observed that the higher cognitive load resulted in lower recall performance, but that this decrease was equivalent for the integrated and the isolated presentation condition. We predict the same

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results in the present study. Concerning the underlying representations that will be measured through the recognition paradigm, Elsley and Parmentier (2009) had suggested that an

integrated maintenance depends on attentional resources. Increasing the cognitive load should thus modify the underlying representations in the integrated presentation condition. This is the only study investigating the involvement of attentional resources in the maintenance of cross-domain associations. However as stated before, the study by Elsley and Parmentier (2009) was based on an implicit binding paradigm and additionally, we had highlighted a pattern of results that was quite unexpected in the light of their conclusion. Several studies on the maintenance of visuo-spatial feature associations, based on an explicit binding paradigm, had in contrast concluded that the maintenance of feature associations does not particularly depend on attention (e.g., Allen et al., 2006; Gajewski & Brockmole, 2006; Vergauwe, Langerock, et al., 2014). In line with these various studies, we predict that object-based maintenance of cross-domain associations is not more dependent on attentional resources than feature-based maintenance.

Method

Participants and Design

Thirty-nine students of the University of Geneva participated in this experiment. Five of them did not pass the training phase and did not continue the experiment. Thirty-four participants (mean age = 22.18 years, SD = 5.90, 26 female) completed both sessions of the experiment. They were paid or received partial course credit. The two sessions corresponded to the integrated and the isolated presentation condition. Cognitive load was manipulated within each session.

Materials and Procedure

Duration and general presentation of the memory items were the same as in

Experiment 6 and the processing task was manipulated as in Experiment 7 (only a low and a high cognitive load and three different tones to discriminate). A comparison between the memory performance of an integrated and an isolated presentation was made making use of a recall and a recognition paradigm. Half of the trials concerned recall trials and the other half concerned recognition trials. Participants did not know whether the presented trial concerned

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a recall or a recognition trial until the moment of test. The recall task was the same as used in Experiment 3, 6 and 7 and the simpler recall procedure as used in Experiment 7 was applied.

For the recognition trials, participants were always tested with a letter in a location. They had to respond “O” (oui - yes) when they had seen both features during the presentation of the features, independently of their association. Both for exact probes (associations as presented before) or for recombinations of features presented before, participants had thus to respond yes. In the integrated presentation mode, these recognition types follow logically from the presentation at study. In the isolated presentation mode, an exact combination was defined as a location with the letter immediately following this location and that could have potentially been associated to this location. A recombination was defined as any other type of

combination of features that had been presented before. Letters could however have been associated to the following location instead of the preceding location. To control for this kind of binding, a distinction was made between “fixed” recombinations, consisting of a letter in serial position x, combined with the location of serial position x+1, and “random”

recombinations for recombinations not following this prerequisite (see Figure 7.3). When one or both of the features at test had not been presented before, participants had to respond “N”

(non - no). This could concern a letter lure, a location lure or an all lure. In 50 % of the recognition trials, participants had to respond yes, and no in the other 50%. Among the positive and negative responses, there was an equal repartition of the recognition probes. For one recognition trial, participants were tested with different probes as many times as twice the list length of that series. So for example at list length three (including thus three letters and three locations to maintain), six recognition probes were presented sequentially.

Figure 7.3: Presentation of the exact, fixed recombination and random combination probes in the isolated presentation condition.

New series of letters and locations were created, ranging from two to six feature pairs.

The created series of letters and locations were randomly displayed per list length, with a random attribution of the memory test (recall or recognition) and cognitive load condition.

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Eight trials (two trials per type of memory test per cognitive load condition) were presented per list length in each of the presentation mode sessions.

Participants first received a training on the recall and recognition task, then on the tone discrimination task and then on the combination of both. Participants had to obtain 80%

accuracy for the tone discrimination task in order to proceed to the actual experiment. It was verified by the experimenter that participants had well understood the instructions, especially for the recognition task.

In this fourth experiment, only the 1500 ms feature presentation time was used for both presentation modes. The procedure for recall trials was the same as used in Experiment 7. For the recognition trials, the procedure was the same, until the moment of test. Once the tone discrimination task ended, participants saw on screen during 1000 ms: “Have you seen the following letter and location” followed by the presentation of a letter in a location that remained on screen until the participant responded yes or no. Then the 1000 ms screen: “Have you seen the following letter and location” appeared again followed by a test probe. This recognition procedure continued until all test probes had been shown. Responses and reaction times were recorded. For the recall trials, span scores were calculated as in the previous experiments for the verbal and spatial domain separately, as well as in terms of cross-domain span scores.

Results

Four participants were excluded as they did not reach an accuracy score of 75 % in the tone discrimination task. Two participants were excluded as their accuracy for recombinations in the recognition task was 0 % in the integrated condition. Although they had given the impression understanding the recognition task during the training phase, their performance in the actual experiment proved that this was not the case. The data of 28 participants were further analyzed for the recall and the recognition task respectively.

Recall

A 2 (Order: integrated - isolated or isolated - integrated) X 2 (Domain: verbal or spatial) X 2 (Presentation mode: integrated or isolated) X 2 (Cognitive load: low or high) repeated measure ANOVA was performed on the verbal and spatial span scores with order as

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between subject factor and domain, presentation mode and cognitive load as within subject factors. Verbal recall performance was better than spatial recall performance, F(1, 26) = 177.54, p < .001, η2 = .87 and a high cognitive load resulted in lower span scores than a low cognitive load, F(1, 26) = 28.63, p < .001, η2 = .52. The effects of order and presentation mode were not significant, F(1, 26) = 1.62, p > .10 and F(1, 26) < 1, pBIC (H0|D) = .83

respectively. There was a significant interaction between domain and cognitive load, F(1, 26)

= 6.83, p = .015. The effect of cognitive load was more pronounced for verbal memory, F(1, 26) = 41.77, p < .001, η2 = .62, than for spatial memory performance, F(1, 26) = 4.69, p = .040, η2 = .15. None of the other interactions reached significance14. The main results are summarized in Table 7.2.

Table 7.2: Span scores (and SD) as a function of presentation mode, domain and cognitive load in Experiment 8.

Spatial Verbal Cross-domain

Low

The same analysis was performed on the cross-domain span scores in a 2 (Order:

integrated - isolated or isolated - integrated) X 2 (Presentation mode: integrated or isolated) X 2 (Cognitive load: low or high) repeated measure ANOVA. Only the effect of cognitive load was significant, F(1, 26) = 8.34, p = .008, η2 = .24. The effects of order and presentation mode were not significant, F(1, 26) = 2.03, p > .10 and F(1, 26) < 1, pBIC (H0|D) = .81 respectively). None of the interactions were significant.

14 The interaction between presentation mode and domain was however marginally significant, F(1, 26)

= 3.57, p = .070, and this was further qualified by a marginally significant triple interaction between presentation mode, domain and cognitive load, F(1, 26) = 3.38, p = .078. The spatial span scores followed an equivalent decrease rate in the integrated and isolated presentation condition, while this decrease rate was more pronounced in the isolated presentation condition for the verbal span scores.

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Recognition

Accuracy

The accuracy scores for the recognition task in the integrated and isolated presentation condition were 80 % (SD = .09) and 81 % (SD = .08) respectively. Table 7.3 shows the accuracy scores per condition and per probe type. We performed a 2 (Order: integrated - isolated or isolated - integrated) X 2 (Presentation mode: integrated or isolated) X 2

(Cognitive load: low or high) X 2 (Probe type: exact, recombined, letter lure, location lure or all lure) repeated measure ANOVA on the accuracy scores with presentation mode, cognitive load and probe type as within subject factors and order as between subject factor. There was a significant effect probe type, F(4, 104) = 26.94, p < .001, η2 = .51. Accuracy for location lures was significantly lower than for recombined probes, F(1, 26) = 4.64, p = .041, which was lower than for exact probes, F(1, 26) = 4.23, p = .050. Accuracy for exact probes was lower than for letter lures, F(1, 26) = 28.97, p < .001, which was equal to accuracy for all lures, F(1, 26) < 1. There was also a significant effect of cognitive load, F(1, 26) = 4.34, p = .047, η2 = .14, with higher accuracy scores in the low cognitive load. The effect of presentation mode was not significant, F(1, 26) < 1, pBIC (H0|D) = .81. There was however a significant

interaction between order and presentation mode, F(1, 26) = 6.75, p = .015. The first session led to lower accuracy scores than the second session. As the order of the sessions was counterbalanced for presentation mode, this resulted in an interaction.

Table 7.3: Accuracy percentage (and SD) as a function of presentation mode, cognitive load and probe type in Experiment 8.

Low CL High CL

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Our main interest was in the comparison between the exact and recombined probes. To focus on these probe types, we reanalyzed the accuracy scores within a 2 (Order: integrated - isolated or isolated - integrated) X 2 (Presentation mode: integrated or isolated) X 2 (Probe type: exact or recombined) X 2 (Cognitive load: low or high) repeated measure ANOVA. We have already reported the significant difference between exact and recombined probes in the analysis above. The effect of cognitive load was still significant, F(1, 26) = 5.84, p = .023, η2

= .18 with higher accuracy scores in the low cognitive load condition. The interaction between presentation mode and probe type was not significant, F(1, 26) < 1. Planned comparisons on the difference between the exact and recombined probes were anyhow

performed for the integrated and isolated conditions, separately for the low and high cognitive load conditions. None of these comparisons reached significance (the difference in the high load condition of the isolated presentation was marginally significant, p = .055).

Reaction times

Reaction times for correct recognition responses were trimmed based on the determination of outliers according to the interquartile range criterion (Tukey, 1977). This procedures defines outliers as the data points that are higher than the third quartile +

1.5*(third quartile – first quartile) or lower than the first quartile – 1.5*(third quartile – first quartile). The higher threshold was 3310 ms. The lower threshold value was < 0 and we excluded hence reaction times below 300 ms as these are considered too fast to reflect an accurate processing reaction time. This trimming procedure resulted in the loss of 8 % of the data. We first analyzed the reaction times according to a 2 (Order: integrated - isolated or isolated - integrated) X 2 (Presentation mode: integrated or isolated) X 2 (Cognitive load: low or high) X 2 (Probe type: exact, recombination, letter lure, location lure or all lure) repeated measure ANOVA with order as between subject factor and presentation mode, cognitive load and probe type as within subject factors. There was a significant effect of cognitive load, F(1, 26) = 7.07, p = .013, η2 = .21, with higher cognitive load leading to shorter reaction times than lower cognitive load. There was also a significant effect of probe type, F(1, 26) = 10.26, p <

.001, η2 = .28. Reaction times for location lures did not differ from reaction times for

recombined probes, F(1, 26) < 1, which were responded to only slightly slower than to exact probes, F(1, 26) = 3.66, p = .067. Exact probes were responded to as fast as letter lures, F(1, 26) < 1, which were in turn responded to slower than to all lures, F(1, 26) = 22.58, p < .001 .

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There was a significant interaction between presentation mode and order, F(1, 26) = 24.48, p

< .001, with the second session resulting in faster reaction times independently of the presentation mode. This interaction was further implied in a triple interaction with cognitive load, F(1, 26) = 6.29, p = .019. The interaction between presentation mode and order was more pronounced in the low cognitive load condition than in the high cognitive load condition. The interaction between presentation mode and probe type was also significant, F(1, 26) = 3.81, p < .006. This interaction will be detailed only for the probes of interest in the analysis below. None of the other effects or interactions were significant. Table 7.4

summarizes the main results.

Table 7.4: Reaction times (and SD) in ms as a function of presentation mode, cognitive load and probe type in Experiment 8.

Low CL High CL

As our main interest was on the comparison between the exact and recombined probes, we reanalyzed the data making use of a 2 (Order: integrated - isolated or isolated - integrated) X 2 (Presentation mode: integrated or isolated) X 2 (Probe type: exact or recombined) X 2 (Cognitive load: low or high) repeated measure ANOVA. As reported above, the difference between the exact and recombined probe was only marginally significant, F(1, 26) = 3.66, p = .067, η2 = .12. The effect of cognitive load was no longer significant, F(1, 26) = 2.40, p > .10.

Presentation mode and order still interacted, F(1, 26) = 24.49, p < .001, and the triple interaction with cognitive load was also still significant, F(1, 26) = 4.27, p = .049. All differences were in line with the differences reported in the analysis above. The interaction between presentation mode and probe type was only marginally significant, F(1, 26) = 3.04, p

= .093. Due to its importance, we performed planned comparisons on the difference between the exact and recombined probe in the integrated and isolated presentation mode. In the integrated condition, exact probes were responded to significantly faster than recombined

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probes, F(1, 26) = 8.77, p = .006, η2 = .25. This difference did not interact with cognitive load, F(1, 26) < 1. In the isolated presentation condition, there was no difference between the exact and recombined probes F(1, 26) < 1, and no interaction with the cognitive load F(1, 26)

< 1. Figure 7.4 represents the results linked to these planned comparisons.

Figure 7.4: Reaction times as a function of presentation mode, probe type and cognitive load in Experiment 8. Error bars represent standard errors.

In the isolated presentation mode, there were no differences in accuracy (77 % and 74

%) or RT (1503 ms and 1458 ms) between the fixed and random recombinations (all p-values

> .20). There was no interaction with cognitive load either (all p-values < .86).

Discussion

The general pattern of results from the recall procedure replicated the results from the previous experiments: an equalization of the feature presentation time in the integrated and isolated presentation of verbal and spatial features resulted in equivalent memory

performance. Additionally, this equivalent memory performance was not more dependent on attentional resources in any of these two conditions. This was demonstrated by the equivalent decrease rates of the span scores in the integrated and isolated presentation condition as a function of the cognitive load.

The recognition paradigm revealed several novel results. In the integrated presentation condition, it was shown that exact probes were responded to faster than recombined probes.

This is exactly what is expected in case of object-based maintenance of the feature

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presentations as the exact probes do not necessitate any reorganization of the feature information. Additionally, faster responses for exact than for recombined probes occurred independently of the cognitive load condition. These results suggest hence the integrated presentation of feature associations to result in object-based maintenance, which is is not dependent on attentional resources. No significant differences were observed between the exact and recombined probes in terms of accuracy in the integrated presentation condition, although the accuracy scores for exact probes were slightly higher than for recombined

probes. Apparently, both probe types can be responded to approximately as accurately. It only takes more time to answer correctly to recombined probes, probably due to a reorganization of the information. The conclusion of object-based maintenance in the integrated presentation condition is thus mainly driven by the analysis on the reaction times, with the results of the accuracy scores however leaning in the same direction. This is in line with the results of Prabhakaran et al. (2000) and Morey (2011), who also found most convincing evidence for integrated maintenance in the pattern of reaction times.

The isolated presentation condition revealed a different pattern of results. In terms of reaction times, there were no differences between the exact and the recombined probes, neither in the low nor high cognitive load condition. No evidence for an object-based maintenance was thus found in the pattern of reaction times. In the integrated condition, it was exactly the pattern of reaction times that led us to conclude to object-based maintenance.

The pattern of accuracy scores in the isolated presentation condition did not reveal any indication of an integrated maintenance either. The accuracy scores for the exact probes were similar to those for the recombined probes in the low cognitive load condition and

tendentiously better in the high cognitive load condition. In case of an object-based

maintenance, if we would have expected any difference, than it would have been especially in the low cognitive load condition, with better accuracy scores for the exact probes. This

difference could then persist in the high cognitive load condition, if this object-based maintenance is not dependent on attentional resource. If object-based maintenance is nevertheless dependent on attentional resources, then we would expect this difference to be lessened in the high cognitive load condition. The accuracy scores we observed in the isolated presentation condition showed rather the opposite pattern. Neither the analysis on the reaction times or the accuracy scores in the isolated presentation condition provided thus any evidence for object-based maintenance.

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An alternative explanation of the results in the isolated presentation condition remained however possible. Both in the integrated and isolated presentation mode, probes consisted of an integrated letter location association. In the integrated presentation condition,

An alternative explanation of the results in the isolated presentation condition remained however possible. Both in the integrated and isolated presentation mode, probes consisted of an integrated letter location association. In the integrated presentation condition,

Dans le document The maintenance of cross-domain associations in working memory (Page 174-189)