Visuospatial working memory and mental representation of spatial descriptions

The purpose of the present research is to investigate whether different components of working memory (WM) are involved in processing spatial and nonspatial texts. The interference effects of two concurrent tasks on comprehension and recall of two kinds of text were investigated in two experiments. Each participant listened to a spatial and a nonspatial text, with one of two concurrent tasks: articulatory suppression or spatial tapping. The dependent variables in Experiment 1 were accuracy of recall and verification of information inferred from the texts. In Experiment 2 response times in the verification task were also considered. Results support the hypothesis that verbal and spatial components of working memory are differentially involved in the comprehension and memory of spatial and nonspatial texts, with a selective interference effect of the spatial concurrent task on the spatial text and an interference effect of the verbal concurrent task on both the spatial and nonspatial texts. These effects emerged for recall, sentence verification, and response times. Our findings confirm previous results showing that the verbal component of working memory is involved in the process of text comprehension and memory. In addition, they show that visuospatial working memory is involved, in so far as the text conveys visuospatial information.     

The role of memory representation in the vigilance decrement

Working memory load is critically important for the overall level of performance on vigilance tasks. However, its role in a key aspect of vigilance—sensitivity decrement over time—is unclear. We used a dual-task procedure in which either a spatial or a nonspatial working memory task was performed simultaneously with a spatial vigilance task for 20 min. Sensitivity in the vigilance task declined over time when the concurrent task involved spatial working memory. In contrast, there was no sensitivity decrement with a nonspatial working memory task. The results provide the first evidence of a specific role for working memory representation in vigilance decrement. The findings are also consistent with a multiple resource theory in which separate resources for memory representation and cognitive control operations are differentially susceptible to depletion over time, depending on the demands of the task at hand.     

Dual-task interference in visual working memory: A limitation in storage capacity but not in encoding or retrieval

The concurrent maintenance of two visual working memory (VWM) arrays can lead to profound interference. It is unclear, however, whether these costs arise from limitations in VWM storage capacity (Fougnie & Maro is, 2006) or from interference between the storage of one visual array and encoding or retrieval of another visual array (Cowan & Morey, 2007). Here, we show that encoding a VWM array does not interfere with maintenance of another VWM array unless the two displays exceed maintenance capacity (Experiments 1 and 2). Moreover, manipulating the extent to which encoding and maintenance can interfere with one another had no discernable effect on dual-task performance (Experiment 2). Finally, maintenance of a VWM array was not affected by retrieval of information from another VWM array (Experiment 3). Taken together, these findings demonstrate that dual-task interference between two concurrent VWM tasks is due to a capacity-limited store that is independent from encoding and retrieval processes.     

Working memory components and imagery instructions in the elaboration of a spatial mental model

The paper investigates the involvement of verbal and visuo-spatial working memory during the processing of spatial texts via a dual-task paradigm. Subjects were presented with three texts describing locations from a route perspective, and had either to imagine themselves moving along a route in surroundings or to rehearse verbal information. Concurrently they had to perform a spatial tapping task, an articulatory task, or no secondary task. Performance on a verification test used to assess the product of comprehension showed that the concurrent tapping task impaired performance in the imagery instructions group but not in the repetition instructions group, and caused the beneficial effect of imagery instructions to vanish. This result was not observed with the articulatory task, where interference effects were similar in both instructions groups. Performance on the concurrent tasks confirmed the pattern obtained with the verification test. In addition, results seem partly dependent on the capacity of spatial working memory as measured by the Corsi Blocks Test. We argue that these results clarify the processes of the construction of a spatial mental model, and confirm that the visuo-spatial working memory is involved in mental imagery.     

Mental representations of spatial and nonspatial relations

Four experiments investigated the representation and integration in memory of spatial and nonspatial relations. Subjects learned two-dimensional spatial arrays in which critical pairs of object names were semantically related (Experiment 1), semantically and episodically related (Experiment 2), or just episodically related (Experiments 3a and 3b). Episodic relatedness was established in a paired-associate learning task that preceded array learning. After learning an array, subjects participated in two tasks: item recognition, in which the measure of interest was priming; and distance estimation. Priming in item recognition was sensitive to the Euclidean distance between object names and, for neighbouring locations, to nonspatial relations. Errors in distance estimations varied as a function of distance but were unaffected by nonspatial relations. These and other results indicated that nonspatial relations influenced the probability of encoding spatial relations between locations but did not lead to distorted spatial memories.     

Temporal-spatial memory: retrieval of spatial information does not reduce recency

Factors influencing the shape of serial position curves in non-verbal serial short-term memory were examined, using a task testing memory for the position of dots. Similar recency slopes were found when both position and order were recalled (Experiment 1A) and when order only was required (Experiment 1B). This observation was confirmed and tested further in conditions requiring the same encoding but different amounts of spatial information at retrieval (Experiment 2). However, Experiment 2 also revealed an effect of spatial information retrieval on the overall level of memory for recency items. Overall, the results indicate that spatial items produce bow-shaped serial positions curves in tasks requiring the maintenance of order information and that recency is affected by the demand on spatial information retrieval in terms of the overall level of performance but not in terms of the recency slope. These findings are contrary to what is found in the literature on serial verbal recall when both item and order information are required.     

The role of spatial working memory in visual search efficiency

Many theories have proposed that visual working memory plays an important role in visual search. In contrast, by showing that a nonspatial working memory load did not interfere with search efficiency, Woodman, Vogel, and Luck (2001) recently proposed that the role of working memory in visual search is insignificant. However, the visual search process may interfere with spatial working memory. In the present study, a visual search task was performed concurrently with either a spatial working memory task (Experiment 1) or a nonspatial working memory task (Experiment 2). We found that the visual search process interfered with a spatial working memory load, but not with a nonspatial working memory load. These results suggest that there is a distinction between spatial and nonspatial working memory in terms of interactions with visual search tasks. These results imply that the visual search process and spatial working memory storage require the same limited-capacity mechanisms.     

Conditional reasoning with a spatial content requires visuo-spatial working memory

In previous research, Toms, Morris, and Ward (1993) have shown that conditional reasoning is impaired by a concurrent task calling on executive functions but not by concurrent tasks that load on the slave systems of the working memory system as conceptualised by Baddeley and Hitch (1974). The present article replicates and extends this previous work by studying problems based on spatial as well as nonspatial relations. In the study 42 participants solved 16 types of spatial or nonspatial problems, both in a single-task condition and under concurrent matrix tapping, a task loading the visuo-spatial sketch pad. The findings were consistent with those of Toms et al. (1993) for problems with a nonspatial content. However, when the content was spatial, and only then, a dual-task impairment was observed: processing time of the first premise was lengthened, especially for problems with negations in the antecedent term, the consequent term, or both; moreover, the number of correctly solved problems with negations in both terms was smaller. The implications of these findings for the mental models theory and the mental logic theory are discussed.     

Exploring the contributions of spatial and non-spatial working memory to priming of pop-out

Priming of pop-out (PoP) refers to the facilitation of performance that occurs when a target-defining feature is repeated across consecutive trials in a pop-out oddball search task. The underlying mechanism of PoP has been poorly understood and raises important questions about how our visual system is guided by past experiences, even during bottom-up processing. Lee, Mozer, and Vecera (Attention, Perception, & Psychophysics, 71, 1059–1071, 2009) demonstrated that PoP remained unaffected by a concurrent non-spatial visual working memory (VWM) load, and they concluded that PoP occurs through feature gain modulation, essentially eliminating the contribution of memory representations in VWM to PoP. In the present study, we followed up on those results by (a) replicating the null effect of non-spatial VWM load on PoP and (b) examining the effect of spatial VWM load on PoP. The results showed that spatial VWM load does interfere with PoP, supporting the notion that spatial VWM is involved in PoP. In Experiment 2, we extended this finding by manipulating VWM load and observing its consequence on the magnitude of PoP. Increasing spatial VWM load decreased the amount of PoP observed, in a dose-dependent manner, whereas changes in non-spatial VWM load did not. Contrary to Lee et al.’s conclusions, these results suggest that VWM resources appear to contribute to the occurrence of PoP, supporting the theory that PoP is, in fact, a multilevel process in which the deployment of spatial attention, relying on VWM representations, plays an important role.     

Visuo‐spatial working memory in navigation

Two experiments employed dual task techniques to explore the role of working memory in route learning and subsequent route retrieval. Experiment 1 involved contrasting performance of two groups of volunteers respectively learning a route from a series of map segments or a series of visually presented nonsense words. Both groups performed learning and recognition under articulatory suppression or concurrent spatial tapping. Both concurrent tasks had an overall disruptive effect on each learning task. However, spatial tapping disrupted route recognition rather more than did articulatory suppression, while the nonsense word recognition was impaired more by articulatory suppression than by concurrent spatial tapping. Experiment 2 again used dual task methodology, but explored route learning by asking volunteers to follow the experimenter through the winding streets of a medieval European town centre. Retrieval involved following the same route while the experimenter followed and noted errors in navigation. Overall the results partially replicated those of Experiment 1 in that both concurrent tasks interfered with route learning. However, volunteers with high spatial ability appeared more affected by the concurrent spatial tapping task, whereas low spatial subjects appeared more affected by the concurrent articulatory suppression task. Results are interpreted to suggest that different aspects of working memory are involved in learning a route from a map with a greater emphasis on visuo‐spatial resources, but in tasks set in real environments where many cues of a varied nature are available, only high spatial ability subjects appear to rely heavily upon the visuospatial component of working memory. Copyright © 2002 John Wiley & Sons, Ltd.     

Mental animation in the visuospatial sketchpad: Evidence from dual-task studies

We used the dual-task paradigm to provide evidence that inferring the motion of a component of a mechanical system (mental animation) is a spatial visualization process. In two experiments, participants were asked to solve mental animation problems while simultaneously retaining either a visuospatial working memory load (a configuration of dots in a grid) or a verbal memory load (a list of letters). Both experiments showed that mental animation interferes more with memory for a concurrent visuospatial load than with memory for a verbal load. Experiment 1 also showed that a visuospatial working memory load interferes more with mental animation than does a verbal memory load. Furthermore, Experiment 2 showed that mental animation interferes more with a visuospatial memory load than does a verbal reasoning task that takes approximately the same amount of time.     

Insensitivity of visual short-term memory to irrelevant visual information

Several authors have hypothesized that visuo-spatial working memory is functionally analogous to verbal working memory. Irrelevant background speech impairs verbal short-term memory. We investigated whether irrelevant visual information has an analogous effect on visual short-term memory, using a dynamic visual noise (DVN) technique known to disrupt visual imagery (Quinn & McConnell, 1996b). Experiment 1 replicated the effect of DVN on pegword imagery. Experiments 2 and 3 showed no effect of DVN on recall of static matrix patterns, despite a significant effect of a concurrent spatial tapping task. Experiment 4 showed no effect of DVN on encoding or maintenance of arrays of matrix patterns, despite testing memory by a recognition procedure to encourage visual rather than spatial processing. Serial position curves showed a one-item recency effect typical of visual short-term memory. Experiment 5 showed no effect of DVN on short-term recognition of Chinese characters, despite effects of visual similarity and a concurrent colour memory task that confirmed visual processing of the characters. We conclude that irrelevant visual noise does not impair visual short-term memory. Visual working memory may not be functionally analogous to verbal working memory, and different cognitive processes may underlie visual short-term memory and visual imagery.     

Exploring the visuo-spatial scratch pad

A series of four studies examines the relationship between the visuo-spatial scratch pad, the central executive and the articulatory loop. For this purpose a visuo-spatial memory task that does not have a large verbal component was developed. In Experiment 1 this task was used to demonstrate that the scratch pad, although functionally independent of the articulatory loop, is subject to interference from a tracking task. Experiment 2 examined the locus of interference of the tracking task with spatial memory. It was shown that interference is confined to the encoding phase; post presentation tracking does not disrupt visuo-spatial representation. Experiment 3 demonstrated that the tracking task employed requires some central executive resources. The final experiment examined the effect of a near-span consonant memory load on the spatial memory task. Disruption only occurred when the verbal load preceded, or was concurrent with, the spatial task. The results suggest that central executive resources are probably required to operate the scratch pad in most circumstances. However, minimal central capacity is required for maintenance rehersal.     

The effect of spatial and nonspatial contextual information on visual object memory

Recent research has found visual object memory can be stored as part of a larger scene representation rather than independently of scene context. The present study examined how spatial and nonspatial contextual information modulate visual object memory. Two experiments tested participants’ visual memory by using a change detection task in which a target object's orientation was either the same as it appeared during initial viewing or changed. In addition, we examined the effect of spatial and nonspatial contextual manipulations on change detection performance. The results revealed that visual object representations can be maintained reliably after viewing arrays of objects. Moreover, change detection performance was significantly higher when either spatial or nonspatial contextual information remained the same in the test image. We concluded that while processing complex visual stimuli such as object arrays, visual object memory can be stored as part of a comprehensive scene representation, and both spatial and nonspatial contextual changes modulate visual memory retrieval and comparison.     

Cross-domain interference costs during concurrent verbal and spatial serial memory tasks are asymmetric

Some evidence suggests that memory for serial order is domain-general. Evidence also points to asymmetries in interference between verbal and visual–spatial tasks. We confirm that concurrently remembering verbal and spatial serial lists provokes substantial interference compared with remembering a single list, but we further investigate the impact of this interference throughout the serial position curve, where asymmetries are indeed apparent. A concurrent verbal order memory task affects spatial memory performance throughout the serial positions of the list, but performing a spatial order task affects memory for the verbal serial list only for early list items; in the verbal task only, the final items are unaffected by a concurrent task. Adding suffixes eliminates this asymmetry, resulting in impairment throughout the list for both tasks. These results suggest that domain-general working memory resources may be supplemented with resources specific to the verbal domain, but perhaps not with equivalent spatial resources.     

Cross-domain interference costs during concurrent verbal and spatial serial memory tasks are asymmetric

Some evidence suggests that memory for serial order is domain-general. Evidence also points to asymmetries in interference between verbal and visual-spatial tasks. We confirm that concurrently remembering verbal and spatial serial lists provokes substantial interference compared with remembering a single list, but we further investigate the impact of this interference throughout the serial position curve, where asymmetries are indeed apparent. A concurrent verbal order memory task affects spatial memory performance throughout the serial positions of the list, but performing a spatial order task affects memory for the verbal serial list only for early list items; in the verbal task only, the final items are unaffected by a concurrent task. Adding suffixes eliminates this asymmetry, resulting in impairment throughout the list for both tasks. These results suggest that domain-general working memory resources may be supplemented with resources specific to the verbal domain, but perhaps not with equivalent spatial resources.     

Visuospatial memory and phonological loop in learning from multimedia

The dual‐task paradigm was used to show how visuospatial working memory and the phonological loop are involved in processing scientific texts and illustrations presented via computer. In experiment 1, two presentation formats were compared: text‐only and text‐with‐illustrations. With a concurrent tapping task, the beneficial effect of illustrations disappeared, while a concurrent articulatory task impaired performance similarly in both presentation formats. An analysis of individual differences revealed that this pattern of results was present in high, but not low spatial span subjects. These results support the selective involvement of visuospatial working memory in processing illustrated texts. In Experiment 2, the text‐only presentation format was compared to an illustrations‐only format. The concurrent articulatory task selectively impaired text‐only processing, compared with processing illustrations‐only. In addition, this pattern of results was found for high, but not low digit span subjects. These results suggest that individual differences define the extent to which the two subsystems of working memory are involved in learning from multimedia. These two subsystems would be mainly involved in the maintenance of a visual trace of illustrations and of a verbatim representation of linguistic information respectively, these representations being the basis for higher‐level comprehension processes. Copyright © 2002 John Wiley & Sons, Ltd.