Poorer divided attention in children born very preterm can be explained by difficulty with each component task,not the executive requirement to dual-task

Children born very preterm (VP, ≤ 32 weeks) exhibit poor performance on tasks of executive functioning. However, it is largely unknown whether this reflects the cumulative impact of non-executive deficits or a separable impairment in executive-level abilities. A dual-task paradigm was used in the current study to differentiate the executive processes involved in performing two simple attention tasks simultaneously. The executive-level contribution to performance was indexed by the within-subject cost incurred to single-task performance under dual-task conditions, termed dual-task cost. The participants included 77 VP children (mean age: 7.17 years) and 74 peer controls (mean age: 7.16 years) who completed Sky Search (selective attention), Score (sustained attention) and Sky Search DT (divided attention) from the Test of Everyday Attention for Children. The divided-attention task requires the simultaneous performance of the selective- and sustained-attention tasks. The VP group exhibited poorer performance on the selective- and divided-attention tasks, and showed a strong trend toward poorer performance on the sustained-attention task. However, there were no significant group differences in dual-task cost. These results suggest a cumulative impact of vulnerable lower-level cognitive processes on dual-tasking or divided attention in VP children, and fail to support the hypothesis that VP children show a separable impairment in executive-level abilities.     

Unidirectional interference in use of nondominant hand during concurrent Grooved Pegboard and random number generation tasks

The interference effect between Grooved Pegboard task with either hand and the executive task of cued verbal random number generation was investigated. 24 normal right-handed subjects performed each task under separate (single-task) and concurrent (dual-task) conditions. Articulatory suppression was required as an additional secondary task during pegboard performance. Analysis indicated an unambiguous distinction between the two hands. Comparisons of single-task and dual-task conditions showed an asymmetrical pattern of unidirectional interference with no practice effects during pegboard performance. Concurrent performance with nondominant hand but not the dominant hand of random number generation performance became continuously slower. There was no effect of divided attention on pegboard performance. Findings support the idea that the nondominant hand on the pegboard and random number tasks draw from the same processing resources but that for the executive aspect random number generation is more sensitive to changes in allocation of attentional resources.     

注意负荷对内隐序列学习的影响研究

运用次级任务研究范式,采用符号计数的次级任务和歧义序列中的次级条件序列,将内隐序列学习分为单任务组和双任务组,统一在单任务条件下测试。结果发现:(1)两组被试内隐学习成绩差异不显著;(2)双任务组被试在学习组块和测试组块的内隐学习差异也不显著。结果进一步支持了在次级任务占用注意资源的条件下内隐学习仍然可以正常地获得、内隐序列学习不受注意负荷影响的观点。     

Attentional load and implicit sequence learning

A widely employed conceptualization of implicit learning hypothesizes that it makes minimal demands on attentional resources. This conjecture was investigated by comparing learning under single-task and dual-task conditions in the sequential reaction time (SRT) task. Participants learned probabilistic sequences, with dual-task participants additionally having to perform a counting task using stimuli that were targets in the SRT display. Both groups were then tested for sequence knowledge under single-task (Experiments 1 and 2) or dual-task (Experiment 3) conditions. Participants also completed a free generation task (Experiments 2 and 3) under inclusion or exclusion conditions to determine if sequence knowledge was conscious or unconscious in terms of its access to intentional control. The experiments revealed that the secondary task impaired sequence learning and that sequence knowledge was consciously accessible. These findings disconfirm both the notion that implicit learning is able to proceed normally under conditions of divided attention, and that the acquired knowledge is inaccessible to consciousness. A unitary framework for conceptualizing implicit and explicit learning is proposed.     

Investigating the visual span in comparative search: the effects of task difficulty and divided attention

In three experiments, participants' visual span was measured in a comparative visual search task in which they had to detect a local match or mismatch between two displays presented side by side. Experiment 1 manipulated the difficulty of the comparative visual search task by contrasting a mismatch detection task with a substantially more difficult match detection task. In Experiment 2, participants were tested in a single-task condition involving only the visual task and a dual-task condition in which they concurrently performed an auditory task. Finally, in Experiment 3, participants performed two dual-task conditions, which differed in the difficulty of the concurrent auditory task. Both the comparative search task difficulty (Experiment 1) and the divided attention manipulation (Experiments 2 and 3) produced strong effects on visual span size.     

Improved intertask coordination after extensive dual-task practice

This study examines whether an improved intertask coordination skill is acquired during extensive dual-task training and whether it can be transferred to a new dual-task situation. Participants practised a visual-manual task and an auditory-vocal task. These tasks were trained in two groups matched in dual-task performance measures before practice: a single-task practice group and a hybrid practice group (including single-task and dual-task practice). After practice, the single-task practice group was transferred to the same dual-task situation as that for the hybrid practice group (Experiment 1), both groups were transferred to a dual-task situation with a new visual task (Experiment 2), and both groups were transferred to a dual-task situation with a new auditory task matched in task difficulty (Experiment 3). The results show a dual-task performance advantage in the hybrid practice group over the single-task practice group in the practised dual-task situation (Experiment 1), the manipulated visual-task situation (Experiment 2), and the manipulated auditory-task situation (Experiment 3). In all experiments, the dual-task performance advantage was consistently found for the auditory task only. These findings suggest that extended dual-task practice improves the skill to coordinate two tasks, which may be defined as an accelerated switching operation between both tasks. This skill is relatively robust against changes of the component visual and auditory tasks. We discuss how the finding of task coordination could be integrated in present models of dual-task research.     

Improved intertask coordination after extensive dual-task practice

This study examines whether an improved intertask coordination skill is acquired during extensive dual-task training and whether it can be transferred to a new dual-task situation. Participants practised a visual–manual task and an auditory–vocal task. These tasks were trained in two groups matched in dual-task performance measures before practice: a single-task practice group and a hybrid practice group (including single-task and dual-task practice). After practice, the single-task practice group was transferred to the same dual-task situation as that for the hybrid practice group (Experiment 1), both groups were transferred to a dual-task situation with a new visual task (Experiment 2), and both groups were transferred to a dual-task situation with a new auditory task matched in task difficulty (Experiment 3). The results show a dual-task performance advantage in the hybrid practice group over the single-task practice group in the practised dual-task situation (Experiment 1), the manipulated visual-task situation (Experiment 2), and the manipulated auditory-task situation (Experiment 3). In all experiments, the dual-task performance advantage was consistently found for the auditory task only. These findings suggest that extended dual-task practice improves the skill to coordinate two tasks, which may be defined as an accelerated switching operation between both tasks. This skill is relatively robust against changes of the component visual and auditory tasks. We discuss how the finding of task coordination could be integrated in present models of dual-task research.     

Investigation on the improvement and transfer of dual-task coordination skills

Recent research has demonstrated that dual-task performance in situations with two simultaneously presented tasks can be substantially improved with extensive practice. This improvement was related to the acquisition of task coordination skills. Earlier studies provided evidence that these skills result from hybrid practice, including dual and single tasks, but not from single-task practice. It is an open question, however, whether task coordination skills are independent from the specific practice situation and are transferable to new situations or whether they are non-transferable and task-specific. The present study, therefore, tested skill transfer in (1) a dual-task situation with identical tasks in practice and transfer, (2) a dual-task situation with two tasks changed from practice to transfer, and (3) a task switching situation with two sequentially presented tasks. Our findings are largely consistent with the assumption that task coordination skills are non-transferable and task-specific. We cannot, however, definitively reject the assumption of transferable skills when measuring error rates in the dual-task situation with two changed tasks after practice. In the task switching situation, single-task and hybrid practice both led to a transfer effect on mixing costs.     

Assessing the automaticity of the exogenous orienting of tactile attention

We examined whether or not abrupt tactile onsets are capable of exogenously capturing tactile spatial attention when visual spatial attention is focused elsewhere. In experiment 1, we compared performance under dual-task conditions (where participants performed a tactile exogenous cuing task and a rapid serial visual presentation--RSVP--task at the same time) with their performance under single-task conditions (where the participants had to perform only the cuing task, although the RSVP stream was still presented in the background) and to a no-stream condition (where only the cuing task was presented). Tactile cuing was completely suppressed in both the dual-task and single-task conditions, showing that exogenous tactile spatial orienting is modulated by visual-spatial attention, which hence appears to be far from truly automatic. In experiment 2, we demonstrated that the abolishment of exogenous tactile orienting was not caused by the transient presentation of abrupt onset stimuli (letters). These results therefore show that exogenous spatial attentional orienting toward abrupt peripheral tactile stimuli is possible as long as perceptual resources are not depleted by a perceptually demanding (RSVP) task.     

Dual-task training reduces impact of cognitive task on postural sway

Postural sway increases when a cognitive task is performed concurrently with a postural task. The author examined the hypothesis that following dual-task training, a concurrent cognitive task would not amplify postural sway. Participants (N = 18) were assigned to no-training, single-task training, or dual-task training groups. Single-task training consisted of 3 sessions in which the postural task, quiet standing on a compliant surface, and the cognitive task, counting backward by 3s, were practiced separately. Dual-task training consisted of 3 sessions of concurrent practice of the cognitive and postural tasks. After training, performance of a concurrent cognitive task increased postural sway in the no-training and single-task training groups but not in the dual-task training group. Results suggest that dual-task practice improves dual-task performance.     

Aging of attention: Does the ability to divide decline?

Previous research has yielded conflicting results regarding the relationship between adult age and the ability to divide attention between two concurrent tasks. At least some of the inconsistency is probably attributable to methodological variations, such as the manner in which divided-attention ability has been assessed, how single-task performance has been considered, and the degree of control over relative emphasis placed on each task. Two experiments employing procedures sensitive to these concerns were conducted in which a speeded decision task was performed during the retention interval of a letter-memory task. The results of both experiments indicated that there were relatively few age-related influences on dual-task performance vis-à-vis those on single-task performance.     

Crossmodal action selection: Evidence from dual-task compatibility

Response-related mechanisms of multitasking were studied by analyzing simultaneous processing of responses in different modalities (i.e., crossmodal action). Participants responded to a single auditory stimulus with a saccade, a manual response (single-task conditions), or both (dual-task condition). We used a spatially incompatible stimulus-response mapping for one task, but not for the other. Critically, inverting these mappings varied temporal task overlap in dual-task conditions while keeping spatial incompatibility across responses constant. Unlike previous paradigms, temporal task overlap was manipulated without utilizing sequential stimulus presentation, which might induce strategic serial processing. The results revealed dual-task costs, but these were not affected by an increase of temporal task overlap. This finding is evidence for parallel response selection in multitasking. We propose that crossmodal action is processed by a central mapping-selection mechanism in working memory and that the dual-task costs are mainly caused by mapping-related crosstalk.     

Interfering with the Central Executive by Means of a Random Interval Repetition Task

Four dual-task experiments are reported in which a short-term memory task is performed concurrently with a random interval repetition task, which was designed to interfere with functions normally attributed to the central executive in the working memory model of Baddeley and Hitch (1974). The task was found to interfere with supra-span serial recall and with backward memory span, but did not disrupt performance on a forward-memoryspan task. The effects were observed in dissociation with effects of articulatory suppression and matrix tapping, so that the locus of the effects of the new task is not due to the slave systems. In addition, single-task random-interval repetition performance was sampled and compared to performance in the dual-task conditions of all four experiments. Although quality of tapping performance differed between the single-task and the dual-task conditions, it was not related to recall performance. All the results are discussed with reference to the working memory model.     

Attention and probabilistic sequence learning

Limitations of using fixed sequences of events in studies of learning in the sequential reaction-time task led us to develop a probabilistic version of the task. When sequences occur probabilistically, transitions usually follow a sequence, but with some small probability, events occur out of sequence. This variation on the paradigm provides new evidence associated with manipulations of attentional load. Most notably, single-task learning leads to particularly high error rates on improbable transitions, suggesting anticipation of the sequence. Dual-task learning shows sensitivity to the sequence (by reaction-time differences to probable and improbable transitions), but without inflated errors on improbable transitions. Sensitivity to the sequence and anticipatory errors disappeared when participants transferred from single-task learning to dual-task conditions, suggesting that what is learned with single-task practice cannot be applied under conditions of limited attention. When learners transferred from dual- to single-task conditions, sensitivity of RT to the sequence increased but anticipation errors remained the same, suggesting that attentional load limits performance, but not learning. Qualitative differences in performance result from variations in attentional resources, which may reflect different learning processes. Received: 17 February 1997 / Accepted: 5 January 1998     

Cognitive load modulates attentional capture by color singletons during effortful visual search

Color singletons that are irrelevant to locating a visual target do not typically capture attention if visual search is effortful. In contrast, when search is efficient color singletons are often found to capture attention. Such distraction by a color singleton can be modulated by single-task vs. dual-task manipulations when visual search is efficient. This is due, presumably, to the increased cognitive load in the dual-task condition, which interferes with top-down attentional control. This study investigated whether capture by a color singleton is also modulated by single-task vs. dual-task manipulations when visual search was effortful. The results of three experiments revealed that attentional capture effects were absent in a single-task condition and were present in a dual-task condition, but only when the identity of the color singleton is not associated with the target response-set. When the identity of the color singleton was relevant to the response-set it captured attention in both the single-task and in dual-task conditions.     

Working-memory capacity, proactive interference, and divided attention: limits on long-term memory retrieval

Two experiments examined how individual differences in working-memory capacity (WM) relate to proactive interference (PI) susceptibility. We tested high and low WM-span participants in a PI-buildup task under single-task or dual-task ("load") conditions. In Experiment 1, a finger-tapping task was imposed during encoding and retrieval of each list; in Experiment 2, tapping was required during encoding or retrieval. In both experiments, low spans showed greater PI than did high spans under no load, but groups showed equivalent PI under divided attention. Load increased PI only for high spans, suggesting they use attention at encoding and retrieval to combat PI. In Experiment 2, only low spans showed a dual-task cost on List 1 memory, before PI built up. Results indicate a role for attentional processing, perhaps inhibitory in nature, at encoding and retrieval, and are discussed with respect to theories of WM and prefrontal cortex function.     

Effect of age on dual-task performance in children and adults

Age effects on dual-task costs were examined in healthy adults (Exp. 1) and in typically developing children (Exp. 2). In both experiments, individual differences in performance on the single-task components were titrated so that any age differences in dual-task costs could not be attributed to differences in single-task performance. Dual-task costs were found, but there were no age-related differences in these costs in older relative to younger adults, in 7-year-old relative to 9-year-old children, or across all four age groups. The results from these experiments suggest that previously reported age differences in dual-task costs, in both healthy ageing and child development, may be due to a failure to adequately equate single-task difficulty.     

Attentional loads associated with interlimb interactions underlying rhythmic bimanual coordination

Studies of rhythmic bimanual coordination under dual-task conditions revealed (1) a dependence of secondary task performance on the stability of coordinative tasks, in that secondary task performance was better during in-phase than antiphase coordination, and (2) a shift in the mean relative phasing between the limbs compared to single-task conditions. The present study aimed to account for these phenomena by dissociating three qualitatively different interactions between the limbs that govern this motor behavior, related to movement planning, error correction, and interlimb reflex activity. The experiment probed the cognitive demands associated with each interlimb interaction by examining the attentional load under dual-task conditions, indexed by reaction times of the secondary task and kinematic changes in the coordinative tasks relative to single-task conditions. First, only in the condition that involved interlimb interactions at the level of movement planning reaction times were shorter for in-phase than for antiphase coordination, highlighting an intimate relation between movement planning and attentional processes. Second, under dual-task conditions a shift in the mean relative phase was observed relative to single-task conditions, but only for the interlimb interactions that depend directly on sensory feedback (error correction and interlimb reflex activity). These observations qualified the effects of attentional load reported in previous studies. Third, reaction times varied systematically over the movement cycle. These variations revealed a dynamical signature of the attentional load that differed between the three interlimb interactions.     

The role of input and output modality pairings in dual-task performance: evidence for content-dependent central interference

Recent debate regarding dual-task performance has focused on whether costs result from limitations in central capacity, and whether central operations can be performed in parallel. While these questions are controversial, the dominant models of dual-task performance share the assumption that central operations are generic--that is, their interactions are independent of stimulus and response modalities. To examine these issues, we conducted a series of dual-task experiments with different input and output modality pairings. One condition combined a visual-manual task with an auditory-vocal task, and the other condition reversed the input-output pairings, combining a visual-vocal task with an auditory-manual task. Input/output modality pairings proved to be a key factor; throughout practice, dual-task costs were generally more than twice as large with visual-vocal/auditory-manual tasks than with the opposite arrangement of modalities (Experiments 1 and 2). These differences could be explained neither by competition for peripheral resources nor by differences in single-task response times (Experiment 3). Moreover, the persistent dual-task costs did not appear to stem from a central bottleneck. Contrary to the dominant models of dual-task performance, we propose that central interference between tasks depends not just on the duration of central operations, nor just strategic adaptation, but also on the content of those operations. Implications for structural and strategic accounts of dual-task interference are discussed.     

Supertaskers: Profiles in extraordinary multitasking ability

Theory suggests that driving should be impaired for any motorist who is concurrently talking on a cell phone. But is everybody impaired by this dual-task combination? We tested 200 participants in a high-fidelity driving simulator in both single- and dual-task conditions. The dual task involved driving while performing a demanding auditory version of the operation span (OSPAN) task. Whereas the vast majority of participants showed significant performance decrements in dual-task conditions (compared with single-task conditions for either driving or OSPAN tasks), 2.5% of the sample showed absolutely no performance decrements with respect to performing single and dual tasks. In single-task conditions, these “supertaskers” scored in the top quartile on all dependent measures associated with driving and OSPAN tasks, and Monte Carlo simulations indicated that the frequency of supertaskers was significantly greater than chance. These individual differences help to sharpen our theoretical understanding of attention and cognitive control in naturalistic settings.