Processing of stimulus properties: Evidence for dual-task integrality.

Assessed the conditions under which dual-task integrality can be fostered by manipulating 4 factors likely to influence the integrality between tasks: intertask redundancy (ITD), the spatial proximity of primary and secondary task displays, the degree to which primary and secondary task displays constitute a single object, and the resource demands of the 2 tasks. The resource allocation policy was inferred from changes in the amplitude of the P300 component of the event-related brain potential. 12 university students participated in 3 experimental sessions in which they performed both single and dual tasks. The primary task was a pursuit step tracking task. The secondary tasks required Ss to discriminate between different intensities or different spatial positions of a stimulus. Task pairs that required the processing of different properties of the same object resulted in better performance than task pairs that required the processing of different objects. These same object-task pairs led to a positive relation between primary task difficulty and the resources allocated to secondary task stimuli. ITD and the physical proximity of task displays produced similar effects of reduced magnitude. (54 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Concurrent validation of a dual-task selection test.

Examined individual differences in dual-task decrement within the framework of a concurrent validation paradigm. The performance of 49 males employed as detection and communication equipment operators aboard military antisubmarine aircraft was measured in a dual-task situation, which combined a visual decision task and an auditory short-term memory task. Criterion scores from a standardized exercise in a radar training simulator were not significantly related to dual-task measures. Peer ratings, supervisor rank orderings based on flight performance, radar training grades, and indexes combining subjective and objective criteria were significantly related to dual-task measures. The dual-task measures, when combined with predictive measures available from aircrew selection tests, enhanced the potential predictive effectiveness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aerobic fitness and cognitive development: Event-related brain potential and task performance indices of executive control in preadolescent children.

The relationship between aerobic fitness and executive control was assessed in 38 higher- and lower-fit children (Mage = 9.4 years), grouped according to their performance on a field test of aerobic capacity. Participants performed a flanker task requiring variable amounts of executive control while event-related brain potential responses and task performance were assessed. Results indicated that higher-fit children performed more accurately across conditions of the flanker task and following commission errors when compared to lower-fit children, whereas no group differences were observed for reaction time. Neuroelectric data indicated that P3 amplitude was larger for higher- compared to lower-fit children across conditions of the flanker task, and higher-fit children exhibited reduced error-related negativity amplitude and increased error positivity amplitude compared to lower-fit children. The data suggest that fitness is associated with better cognitive performance on an executive control task through increased cognitive control, resulting in greater allocation of attentional resources during stimulus encoding and a subsequent reduction in conflict during response selection. The findings differ from those observed in adult populations by indicating a general rather than a selective relationship between aerobic fitness and cognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Executive control of cognitive processes in task switching.

In 4 experiments, participants alternated between different tasks or performed the same task repeatedly. The tasks for 2 of the experiments required responding to geometric objects in terms of alternative classification rules, and the tasks for the other 2 experiments required solving arithmetic problems in terms of alternative numerical operations. Performance was measured as a function of whether the tasks were familiar or unfamiliar, the rules were simple or complex, and visual cues were present or absent about which tasks should be performed. Task alternation yielded switching-time costs that increased with rule complexity but decreased with task cuing. These factor effects were additive, supporting a model of executive control that has goal-shifting and rule-activation stages for task switching. It appears that rule activation takes more time for switching from familiar to unfamiliar tasks than for switching in the opposite direction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aging and dual-task performance: A meta-analysis.

The relations between dual-task effects and aging were examined through a meta-analysis of 33 studies (with 48 independent participant groups) using latency as the dependent measure and 30 studies (with 40 independent participant groups) focusing on accuracy. Brinley plots and state traces were derived, and a model to explicate different types of complexity (additive and multiplicative) was developed. The effects of dual-task processing on latency were additive, and this additive cost was larger in older adults than in younger adults and larger than predicted from general slowing. This cost was small and independent of task complexity. The effects of dual-task processing on logit-transformed accuracy were likewise additive, but no specific age deficit was associated with this dual-task cost. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence that task performance should be distinguished from contextual performance.

Tests the merit of the distinction made by W. C. Borman and S. J. Motowidlo (1993) between task performance and contextual performance. Supervisors rated 421 US Air Force mechanics on their task performance, contextual performance, and overall performance. Data on length of Air Force experience, ability, training performance, and personality were also available for many of these mechanics. Results show that both task performance and contextual performance contribute independently to overall performance. Experience is more highly correlated with task performance than with contextual performance, and personality variables are more highly correlated with contextual performance than with task performance. These results support the distinction between task performance and contextual performance and confirm that performance, at least as judged by supervisors is multidimensional. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preschool executive control on the Shape School task: Measurement considerations and utility.

Executive functions (EF) necessary for purposeful goal-directed activities undergo rapid change and development during the preschool years. However, of the few psychometrically valid measures of EF suitable for use with preschoolers, information on task sensitivity and predictive validity is scant. The neurodevelopmental correlates of early executive difficulties are also largely unknown. In this study, the discriminant and predictive validity of the recently developed Shape School task (Espy, Bull, Martin, & Stroup, 2006) was examined with data from a regional sample of 209 preschool children at age 4 years. A 2-tiered measurement approach was used, with task completion examined in addition to efficiency. Children's performance was also examined in relation to functioning in a range of neurodevelopmental domains. The Shape School task showed some usefulness in capturing expected differences between at-risk and typically developing children. Performance loaded heavily on language and global cognitive abilities. However, several other factors were also implicated, including attention, motor skills, and ocular control. In addition, task completion and efficiency scores appeared to reflect different aspects of performance, and their associations with neurodevelopmental function and later academic achievement on the Woodcock-Johnson Tests of Achievement at age 6 years also differed. Implications for the application of the Shape School task are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Multiple systems for cognitive control: Evidence from a hybrid prime-Simon task.

Cognitive control resolves conflicts between appropriate and inappropriate response tendencies. Is this achieved by a unitary all-purpose conflict control system, or do independent subsystems deal with different aspects of conflicting information? In a fully factorial hybrid prime-Simon task, participants responded to the identity of targets displayed at different nominally irrelevant screen locations, preceded by nominally irrelevant, consciously or nonconsciously perceived primes. The response required by the target's identity could match or mismatch (a) the target's location, and (b) the prime's identity, resulting in potential conflict (a) across and (b) within stimulus domains. Conflict effects were investigated within and across trials. Results suggest that (i) nonconsciously perceived information elicits within-trial control, but—unlike consciously perceived information—no across-trial behavioral modulation; (ii) separate subsystems deal with conflicts arising from different stimulus domains; and (iii) occasional apparent interactions between domains reflect a particular difficulty in reactivating a just-discarded response (reactivation aversion effect, RAE). (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The impact of comparison processes on coactors' task performance.

Conducted 2 experiments with 135 female undergraduates to investigate the operation of social comparison processes within coaction. Perceived discrepancies between coactors' performance levels were induced by altering their feedback schedules. An S was paired with a coactor who seemed to be performing either at a superior, inferior, or similar level. The pattern of results suggests that comparison processes are active components within coaction. An expectation/criterion level interpretation is discussed within a social comparison analysis. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age differences in dual-task performance after practice.

This study investigated whether older adults could acquire the ability to perform 2 cognitive operations in parallel in a paradigm in which young adults had been shown to be able to do so (K. Oberauer & R. Kliegl, 2004). Twelve young and 12 older adults practiced a numerical and a visuospatial continuous memory updating task in single-task and dual-task conditions for 16 to 24 sessions. After practice, 9 young adults were able to process the 2 tasks without dual-task costs, but none of the older adults had reached the criterion of parallel processing. The results suggest a qualitative difference between young and older adults in how they approach dual-task situations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Changes in executive control across the life span: Examination of task-switching performance.

A study was conducted to examine changes in executive control processes over the life span. More specifically, changes in processes responsible for preparation and interference control that underlie the ability to flexibly alternate between two different tasks were examined. Individuals (N?=?152) ranging in age from 7 to 82 years participated in the study. A U-shaped function was obtained for switch costs (i.e., the time required to switch between tasks compared with a repeated-task baseline), with larger costs found for young children and older adults. Switch costs were reduced with practice, particularly for children. All age groups benefited from increased preparation time, with larger benefits observed for children and older adults. Adults benefited to a greater extent than children when the interval between the response to one task and the cue indicating which task to perform next was lengthened, which suggested faster decay of interference from the old task set for adults than for children. A series of hierarchical analyses indicated that the age-related variance in task-switching performance is independent, at least in part, from the age-related variance in other cognitive processes such as perceptual speed and working memory. The results are discussed in terms of the development and decline of executive control processes across the life span. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of electronic performance monitoring on personal control, task satisfaction, and task performance.

A laboratory study was conducted to assess effects of electronic performance monitoring on individuals working on computers in an officelike environment. Participants (N ?=?108) worked on a computerized data correction task under 6 experimental conditions that varied the amount of control over performance monitoring and knowledge concerning specific monitoring events. Results confirmed and extended a model proposed by D. B. Greenberger and S. Strasser (1986) to relate personal control, satisfaction, and performance. Participants with the ability to delay or prevent electronic performance monitoring indicated higher feelings of personal control and demonstrated superior task performance. Participants with exact knowledge of the occurrence of monitoring expressed lower feelings of personal control than those from whom specific knowledge of monitoring was hidden. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A computational theory of executive cognitive processes and multiple-task performance: Part I. Basic mechanisms.

A new theoretical framework, executive-process interactive control (EPIC), is introduced for characterizing human performance of concurrent perceptual-motor and cognitive tasks. On the basis of EPIC, computational models may be formulated to simulate multiple-task performance under a variety of circumstances. These models account well for reaction time (RT) data from representative situations such as the psychological refractory-period procedure. EPlC's goodness of fit supports several key conclusions: (a) At a cognitive level, people can apply distinct sets of production rules simultaneously for executing the procedures of multiple tasks; (b) people's capacity to process information at "peripheral" perceptual-motor levels is limited; (c) to cope with such limits and to satisfy task priorities, flexible scheduling strategies are used; and (d) these strategies are mediated by executive cognitive processes that coordinate concurrent tasks adaptively. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Process interference and code overlap in dual-task performance.

Perceptual encoding processes have recently been shown to interfere with response selection in dual tasks (P. Jolicoeur & R. Dell'Acqua, 1998). Spatial cross-task compatibility (CTC) was varied to additionally manipulate code overlap across tasks. A new response-cuing paradigm was devised, in which a stimulus movement was used for later report in a perceptual task and a finger movement was used as response in a logically independent reaction task. Three experiments were conducted showing dual-task process interference, but shorter reaction times with CTC than without were also observed. This CTC priming effect was largest with high temporal overlap between the perception and reaction stimuli. The CTC effect was interpreted as resulting from overlap of code activation across tasks, whereas process interference seems to occur to prevent temporal overlap on the level of perceptual encoding and response retrieval processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory and the control of action: Evidence from task switching.

A series of 7 experiments used dual-task methodology to investigate the role of working memory in the operation of a simple action-control plan or program involving regular switching between addition and subtraction. Lists requiring switching were slower than blocked lists and showed 2 concurrent task effects. Demanding executive tasks impaired performance on both blocked and switched lists, whereas articulatory suppression impaired principally the switched condition. Implications for models of task switching and working memory and for the Vygotskian concept of verbal control of action are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence for executive dysfunction in autism

A group of young people with autism (ranging in ability from high functioning to moderately learning disabled), and ability-matched control groups of (i) non-autistic individuals with moderate learning disabilities, and (ii) normally developing children, were presented with two tests of executive function: the Intra-dimensional/Extra-dimensional set-shifting task and the Tower of London planning task. These tests were graded in difficulty and included internal control measures. On each task, the autistic group was differentially impaired with respect to both control groups. Moreover, this impairment was specific to the stages of each task which placed greatest demands upon executive control. This evidence for executive dysfunction in autism is discussed in the context of Norman and Shallice's (Centre for Human Information Processing Technical Report 99, 1980) "Supervisory Attentional System" model of frontal function.     

Automatic stimulus–response translation in dual-task performance.

In bottleneck models of overlapping-task performance, stimulus-response translation for secondary tasks is postponed until the primary response is selected. If this is so, then compatibility between the secondary and primary responses, or between the secondary response and the primary stimulus, should not affect primary-task performance. Yet such effects were demonstrated in 5 dual-task experiments combining primary manual and secondary vocal tasks: Pronounced effects of compatibility between the secondary and primary response and between the secondary response and primary stimulus were found on primary-task performance. The latter effect was also found with the lowest level of an extensive stimulus onset asynchrony variation, when the secondary task was not speeded, and even when the 2 tasks were performed on different trials. Findings suggest that secondary responses were activated before primary response selection was completed and thus support an automatic-translation hypothesis holding that, although eventual response selection may be serial, stimulus-response translation is performed in parallel. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociating consciousness from inhibitory control: Evidence for unconsciously triggered response inhibition in the stop-signal task.

Theories about the functional relevance of consciousness commonly posit that higher order cognitive control functions, such as response inhibition, require consciousness. To test this assertion, the authors designed a masked stop-signal paradigm to examine whether response inhibition could be triggered and initiated by masked stop signals, which inform participants to stop an action they have begun. In 2 experiments, masked stop signals were observed to occasionally result in full response inhibition as well as to yield a slow down in the speed of responses that were not inhibited. The magnitude of this subliminally triggered response time slowing effect correlated with the efficiency measure (stop signal reaction time) of response inhibition across participants. Thus, response inhibition can be triggered unconsciously—more so in individuals who are good inhibitors and under conditions that are associated with efficient response inhibition. These results indicate that in contradiction to common theorizing, inhibitory control processes can operate outside awareness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Training effects on dual-task performance: Are there age-related differences in plasticity of attentional control?

A number of studies have suggested that attentional control skills required to perform 2 tasks concurrently become impaired with age (A. A. Hartley, 1992; J. M. McDowd & R. J. Shaw, 2000). A. A. Hartley (2001) recently observed that the age-related differences in dual-task performance were larger when the 2 tasks required similar motor responses. The present study examined the extent to which age-related deficits in dual-task performance or time sharing--in particular, dual-task performance of 2 discrimination tasks with similar motor requirements--can be moderated by training. The results indicate that, even when the 2 tasks required similar motor responses, both older and younger adults could learn to perform the tasks faster and more accurately. Moreover, the improvement in performance generalized to new task combinations involving new stimuli. Therefore, it appears that training can substantially improve dual-task processing skills in older adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory impairments in multiple sclerosis: Evidence from a dual-task paradigm.

The aim of this study was to investigate working memory in multiple sclerosis (MS) patients. To test the hypothesis that the central executive system (CES) of working memory is impaired, 36 MS patients were administered a dual-task paradigm in which a judgment of line orientation measure was performed concurrently with finger tapping, humming a melody, or reciting the alphabet. MS patients exhibited a significantly greater decrement in performance than controls during the more demanding dual-task conditions (concurrent humming or alphabet recitation) as compared with the single-task condition. Dual-task performance in MS patients correlated with performance on the Paced Auditory Serial Addition Test but not with other cognitive or clinical measures. The authors conclude that MS patients have a working memory deficit reflecting an impaired central executive system. Moreover, impairments in speed of information processing in MS patients are associated with this CES deficit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)