Scoping review of dual-task interference in individuals with intellectual disability

Dual-task paradigms can provide insights on the structures and mechanisms underlying information processing and hold diagnostic, prognostic, and rehabilitative value for populations with cognitive deficits such as in individuals with intellectual disability (ID). In this paradigm, two tasks are performed separately (single-task context) and concurrently (dual-task context). The change in performance from single- to dual-task context represents dual-task interference. Findings from dual-task studies have been largely inconsistent on whether individuals with ID present with dual-task-specific deficits. The current review aimed to map the published literature on dual-task methods and pattern of dual-task interference in individuals with ID. A scoping review based on Arksey and O'Malley's five-stage methodological framework was performed. Seventeen electronic databases and registries were searched to identify relevant studies, including gray literature. Charted data from included studies were analyzed quantitatively and qualitatively. PRISMA guidelines informed the reporting of this review. Twenty-two studies involving 1,102 participants (656 with ID and 446 without ID) met the review's inclusion criteria. Participants in the included studies were heterogeneous in sex, age (range 3-59 years), etiology and ID severity. Included studies characterized their ID-sample in different ways, most commonly using intelligence quotient (IQ) scores. Other measures of intellectual function (e.g., mental age, ID severity, verbal and/or visuospatial ability scores) were also used, either solely or in combination with IQ. Methods of dual-task testing varied across studies, particularly in relation to dual-task combinations, equation of single-task performance between groups, measurement and reporting of dual-task performance for each single-task, and task priority instructions. Thematic content of the included studies were: (1) structural interference to dual-tasking; (2) etiology-based differences in dual-tasking; (3) gait and balance dual-task performance; (4) testing executive function using dual-task paradigms; and (5) training effect on dual-task performance. Although the evidence consistently supported the intact dual-tasking ability of individuals with ID, the pattern of dual-task interference was inconsistent. Likewise, the evidence was inconclusive regarding dual-task deficit specific to individuals with ID because of heterogeneity in dual-task study designs among included studies.

Athletes with intellectual disability: The effects of cognitive deficits and sports practice on bipedal standing balance

BACKGROUND

Athletes with intellectual disability represent a unique population who experiences the contrasting effects of cognitive deficits and benefits of sports on balance. This study investigated the combined impact of intellectual disability and sport practice on balance.

METHOD

Center-of-pressure excursion in bipedal stance of 2 disability (with and without intellectual disability) × 2 sport practice (athlete and novice) participant groups was measured in several balance conditions.

RESULTS

Sport practice exerted no significant effect on any of the center-of-pressure measures used. In contrast, intellectual disability's effects on balance, which were most apparent in challenging balance conditions, were significant (p < .05) and had large effect sizes (η_p ²  > 0.13).

CONCLUSION

The negative effects of cognitive deficits on the balance of young adults with intellectual disability underscore the need for effective interventions. Although findings did not support sports' balance-remediating potential, the value of sport participation for individuals with intellectual disability cannot be fully dismissed just yet.

Cognitive-motor multitasking in athletes with and without intellectual impairment

PURPOSE

We investigated cognitive-motor multitasking in 29 top athletes with intellectual impairment (II) recruited during the European Championship Games organized by Virtus (World Intellectual Impairment Sports) and 29 control (CT) athletes matched for age, sex, sports practiced, and lifetime accumulated practice hours.

METHODS

Participants performed a cognitive task that required recognizing previously displayed visual objects among distractors. The motor task required maintaining a stable upright posture balancing on a rocking board placed atop a force plate which assessed center-of-pressure (COP) movement. Both tasks were performed separately (with participants seated for the cognitive single task) and concurrently under dual-task conditions, wherein participants memorized objects while balancing. We analyzed recognition accuracy, COP path length, and sample entropy of the COP trajectory as a measure for automaticity of postural control.

RESULTS

As expected, CT-athletes outperformed II-athletes in the cognitive task but the two groups have comparable performance in the postural task under single- and dual-task conditions. When multitasking, CT-athletes switched to more automatic postural control and maintained their postural sway at single-task levels. II-athletes prioritized balance thereby successfully keeping COP excursion comparable to single-task conditions. However, this came with pronounced costs for memory performance, which was unaffected by multitasking in CT-athletes.

CONCLUSION

The adaptive capacity observed in control athletes was not at the disposal of II-athletes who revealed pronounced sensitivities to multitasking interference. This sensitivity obviously was not compensated for by either athletic competence or potential transfer of athletic skill to domain-general cognitive functions.

Reliability of center of pressure excursion as a measure of postural control in bipedal stance of individuals with intellectual disability: A pilot study

The high prevalence of postural instability in individuals with intellectual disability (ID) warrants the need for reliable and practical postural control assessments. Stabilometry is a postural control assessment that has been widely used for clinical populations. However, the scant systematic knowledge about the reliability of stabilometric protocols for adults with ID renders results questionable and limits its value for clinicians and researchers. The study's purpose was to develop a stabilometric protocol for adults with and without ID based on optimal combinations of shortest necessary trial durations and the least number of trial repetitions that guarantee sufficient reliability. Participants performed six trials of bipedal standing in 2 vision (eyes open vs eyes closed) x 2 surface (solid vs compliant) conditions on a force platform. Several parameters were calculated from the first 10-, 20-, and 30-s interval of every center-of-pressure (COP) trial data. For different trial durations, we identified the number of trials that yielded acceptable relative (intraclass correlation coefficient ≥ 0.70) and absolute (standard error of measurement < 20%) reliability using the Spearman-Brown prophecy formula. To determine the optimal combination of trial duration and number of repetition for each COP parameter, we implemented a two-step process: 1) identify the largest number of repetition for each of the three trial durations and then 2) select the trial duration with the lowest number of repetition. For both ID- and non-ID groups, we observed a trend whereby shorter trial durations required more repetitions and vice versa. The phase plane and ellipse area were the most and least reliable center-of-pressure parameter, respectively. To achieve acceptable reliability, four 30-s trials of each experimental condition appeared to be optimal for testing participants with and without ID alike. The results of this research can inform stabilometric test protocols of future postural control studies of adults with ID.

Grouping by proximity in haptic contour detection

We investigated the applicability of the Gestalt principle of perceptual grouping by proximity in the haptic modality. To do so, we investigated the influence of element proximity on haptic contour detection. In the course of four sessions ten participants performed a haptic contour detection task in which they freely explored a haptic random dot display that contained a contour in 50% of the trials. A contour was defined by a higher density of elements (raised dots), relative to the background surface. Proximity of the contour elements as well as the average proximity of background elements was systematically varied. We hypothesized that if proximity of contour elements influences haptic contour detection, detection will be more likely when contour elements are in closer proximity. This should be irrespective of the ratio with the proximity of the background elements. Results showed indeed that the closer the contour elements were, the higher the detection rates. Moreover, this was the case independent of the contour/background ratio. We conclude that the Gestalt law of proximity applies to haptic contour detection.

Lifespan changes in multi-tasking: concurrent walking and memory search in children, young, and older adults

We investigated dual-task performance of cognitive (semantic fluency) and sensorimotor tasks (walking) in 120 children and adults from four age groups (9-year olds, M=9.52 years; 11-year olds, M=11.51 years; young adults, M=25.34 years; older adults, M=64.28 years; N=30 per group). Distances walked during 90 s and numbers of category exemplars generated in the semantic fluency task showed an inverted U-shape function with age. In line with general resource models proportional dual-task costs in walking also showed a U-shaped relation as a function of age with pronounced decrements in the youngest and oldest groups. Only 9-year olds showed significant costs in the cognitive task. Individual differences in single-task performance accounted for more than half of the variance in dual-task performance. Reliable age-related residual variance implicated additional factors particularly in children's developing multi-tasking performances.

Adaptation and reintegration of proprioceptive information in young and older adults' postural control

We investigated age-related changes in adaptation and sensory reintegration in postural control without vision. In two sessions, participants adapted their posture to sway reference and to reverse sway reference conditions, the former reducing (near eliminating) and the latter enhancing (near doubling) proprioceptive information for posture by means of support-surface rotations in proportion to body sway. Participants stood on a stable platform for 3 min (baseline) followed by 18 min of sway reference or reverse sway reference (adaptation) and finally again on a stable platform for 3 min (reintegration). Results showed that when inaccurate proprioception was introduced, anterior-posterior (AP) sway path length increased in comparable levels in the two age groups. During adaptation, young and older adults reduced postural sway at the same rate. On restoration of the stable platform in the reintegration phase, a sizeable aftereffect of increased AP path length was observed in both groups, which was greater in magnitude and duration for older adults. In line with linear feedback models of postural control, spectral analyses showed that this aftereffect differed between the two platform conditions. In the sway-referenced condition, a switch from low- to high-frequency COP sway marked the transition from reduced to normal proprioceptive information. The opposite switch was observed in the reverse sway referenced condition. Our findings illustrate age-related slowing in participants' postural control adjustments to sudden changes in environmental conditions. Over and above differences in postural control, our results implicate sensory reweighting as a specific mechanism highly sensitive to age-related decline.

Working memory and postural control: adult age differences in potential for improvement, task priority, and dual tasking

We investigate dynamic posture control and working memory (NBack) retest practice in young and older adults, focusing on older adults' potential for improvement in the component tasks but more importantly in dual-task performance. Participants performed the 2 tasks in 11 sessions under single- and dual-task conditions. Posture improvement was observed with retest practice for both groups. Increase in cognitive load after initial practice led to greater dual-task costs in both tasks in older adults and higher costs in memory in young adults. With continued practice, costs were reduced by both groups; however, the 2 groups focused improvement on different tasks: Older adults focused on posture but young adults on cognition. These results emphasize older adults' potential for improvement in dual-task performance and their flexibility to utilize the practice gains in posture to optimize cognitive performance.

Age differences between children and young adults in the dynamics of dual-task prioritization: body (balance) versus mind (memory)

Task prioritization can lead to trade-off patterns in dual-task situations. The authors compared dual-task performances in 9- and 11-year-old children and young adults performing a cognitive task and a motor task concurrently. The motor task required balancing on an ankle-disc board. Two cognitive tasks measured working memory and episodic memory at difficulty levels individually adjusted during the course of extensive training. Adults showed performance decrements in both task domains under dual-task conditions. In contrast, children showed decrements only in the cognitive tasks but actually swayed less under dual-task than under single-task conditions and continued to reduce their body sway even when instructed to focus on the cognitive task. The authors argue that children perform closer to their stability boundaries in the balance task and therefore prioritize protection of their balance under dual-task conditions.

Can we create gifted people?

Only in the light of specific theoretical frameworks for the development of superior performance can we productively ask to what extent that performance is due to controllable external factors and thus could potentially be engineered or 'created'. The popular view of talent acknowledges that instruction and practice are necessary but not sufficient for the attainment of élite performance. With extensive practice individuals are assumed to achieve all possible modification through learning, so that the ultimate level of performance is a function of the components that cannot be modified and are thus presumably innate. However, recent research shows that improvements in performance are possible even after extensive experience in a domain, and that performance at an international level requires over ten years of intense preparation. Furthermore, research has failed to specify and measure talent factors that predict performance. An alternative framework has been proposed on the basis of the amount of deliberate activities aimed at improving performance. The amount of deliberate practice accumulated during many years of preparation is found to be related closely to performance, even at the highest levels. This framework accounts for expert performance in terms of acquired characteristics and identifies new and different constraints on its attainment.

Adaptive task prioritization in aging: selective resource allocation to postural control is preserved in Alzheimer disease

OBJECTIVE

With age, the performance of multiple tasks decreases, a pattern exaggerated in Alzheimer disease (AD). At the same time, recent research, based on adaptive theories of healthy aging, indicates a preference of older adults to allocate resources toward tasks of higher immediate value (e.g., postural control). This study investigated whether such models also hold for pathologic cognitive aging.

METHOD

Using a dual-task paradigm, the authors combined a working memory with a postural control task under easy and difficult conditions in patients with AD, older adults, older adults low on performance on a cognitive marker test, and young adults (N = 40). Participants repeatedly performed a cognitive and a postural control task both simultaneously and in isolation over the course of eight sessions.

RESULTS

Consistent with earlier studies on divided attention in age and AD, the authors found large dual-task performance decrements with age and more so in AD. When not challenged, patients with AD showed large performance decrements under dual-task conditions in both postural control and working memory. With increasing difficulty in the postural control task, however, older adults, and more so patients with AD, maintained a high level of functioning in postural control, as compared with working memory.

CONCLUSION

The findings indicate that the theory of selective optimization with compensation extends to pathologic aging and have broad implications for models of dual-task performance and executive control in aging and AD.

Timing, sequencing, and executive control in repetitive movement production

The authors demonstrate that the timing and sequencing of target durations require low-level timing and executive control. Sixteen young (M-sub(age) = 19 years) and 16 older (M-sub(age) = 70 years) adults participated in 2 experiments. In Experiment 1, individual mean-variance functions for low-level timing (isochronous tapping) and the sequencing of multiple targets (rhythm production) revealed (a) a dissociation of low-level timing and sequencing in both age groups, (b) negligible age differences for low-level timing, and (c) large age differences for sequencing. Experiment 2 supported the distinction between low-level timing and executive functions: Selection against a dominant rhythm and switching between rhythms impaired performances in both age groups and induced pronounced perseveration of the dominant pattern in older adults.

[Allocation of cognitive resources during the simultaneous performance of cognitive and sensorimotor tasks]

We review research on the allocation of cognitive resources during the simultaneous performance of cognitive and sensorimotor tasks. From the developmental and clinical perspectives,we emphasize: (1) the distinction between the availability and the allocation of resources, (2) lifespan changes in relation to the environmental validity of sensorimotor functions, and (3) the potentials and limitations for an individuals' adaptations to multi-task constraints. These aspects can be operationalized within the framework of selection, optimization, and compensation (SOC). Related studies focus on older individuals' selective resource allocation and compensatory processes as adaptive means in the context of reduced resources and decreased sensorimotor functioning. Results show that older adults must invest increasing amounts of their cognitive resources into the coordination of bodily functions such as balance and gait. SOC research on Alzheimer's patients provides new insights into the increased risks of falling. We argue that adaptive resource allocation in everyday sensorimotor performance is an instance of intelligent behavior that is insufficiently represented in extant psychometric tests.

Aging, expertise and fine motor movement

Age-graded decrements in accuracies and maximum speed of fine motor movements observed in numerous experimental studies have nurtured general factor explanations like the assumption of general age-related slowing of central cognitive processes. This review focuses on two domains of investigation that yielded challenges to general factor models. First, experimental approaches aiming at the decomposition of fine motor skills provide evidence for the dissociability of timing, sequencing, and executive control components that show differential rather than general age-related changes. Second, studies on cognitive-motor expertise demonstrate that age-related changes in critical skill components depend on individuals' time investments into specific practice activities. It is argued that the process dissociations observed at the behavioral level in developmental (i.e. age and expertise) studies reflect individuals' long-term adaptations to internal and external performance constraints. The outcomes of these adaptation processes are stable interindividual differences in component processes.

Synchronizing movements with the metronome: nonlinear error correction and unstable periodic orbits

The control of human hand movements is investigated in a simple synchronization task. We propose and analyze a stochastic model based on nonlinear error correction; a mechanism which implies the existence of unstable periodic orbits. This prediction is tested in an experiment with human subjects. We find that our experimental data are in good agreement with numerical simulations of our theoretical model. These results suggest that feedback control of the human motor systems shows nonlinear behavior.

Age-specific problems in rhythmic timing

The authors investigated performance in 2 rhythm tasks in young (M = 23.8 years) and older (M = 71.4 years) amateur pianists to test whether slowing of a central clock can explain age-related changes in timing variability. Successive keystrokes in the rhythm tasks were separated by either identical (isochronous) time intervals or varying (anisochronous) intervals. Variability was comparable for young and older adults in the isochronous task; pronounced age effects were found for the anisochronous rhythm. Analyses of covariances between intervals rule out slowing of a central clock as an explanation of the findings, which instead support the distinction between target specification, timekeeper execution, and motor implementation proposed by the rhythm program hypothesis (D. Vorberg & A. M. Wing, 1996). Age stability was found at the level of motor implementation, but there were age-related deficits for processes related to target-duration specification.

The fast and the slow of skilled bimanual rhythm production: parallel versus integrated timing

Professional pianists performed 2 bimanual rhythms at a wide range of different tempos. The polyrhythmic task required the combination of 2 isochronous sequences (3 against 4) between the hands; in the syncopated rhythm task successive keystrokes formed intervals of identical (isochronous) durations. At slower tempos, pianists relied on integrated timing control merging successive intervals between the hands into a common reference frame. A timer-motor model is proposed based on the concepts of rate fluctuation and the distinction between target specification and timekeeper execution processes as a quantitative account of performance at slow tempos. At rapid rates expert pianists used hand-independent, parallel timing control. In alternative to a model based on a single central clock, findings support a model of flexible control structures with multiple timekeepers that can work in parallel to accommodate specific task constraints.

The fast and the slow of skilled bimanual rhythm production: parallel versus integrated timing

Professional pianists performed 2 bimanual rhythms at a wide range of different tempos. The polyrhythmic task required the combination of 2 isochronous sequences (3 against 4) between the hands; in the syncopated rhythm task successive keystrokes formed intervals of identical (isochronous) durations. At slower tempos, pianists relied on integrated timing control merging successive intervals between the hands into a common reference frame. A timer-motor model is proposed based on the concepts of rate fluctuation and the distinction between target specification and timekeeper execution processes as a quantitative account of performance at slow tempos. At rapid rates expert pianists used hand-independent, parallel timing control. In alternative to a model based on a single central clock, findings support a model of flexible control structures with multiple timekeepers that can work in parallel to accommodate specific task constraints.

Maintaining excellence: deliberate practice and elite performance in young and older pianists

Two studies investigated the role of deliberate practice in the maintenance of cognitive-motor skills in expert and accomplished amateur pianists. Older expert and amateur pianists showed the normal pattern of large age-related reductions in standard measures of general processing speed. Performance on music-related tasks showed similar age-graded decline for amateur pianists but not for expert pianists, whose average performance level was only slightly below that of young expert pianists. The degree of maintenance of relevant pianistic skills for older expert pianists was predicted by the amount of deliberate practice during later adulthood. The role of deliberate practice in the active maintenance of superior domain-specific performance in spite of general age-related decline is discussed.

Sequential and coordinative processing dynamics in figural transformations across the life span

This work tests the proposition that two distinct factors involved in life span cognitive development are mental speed and coordination efficiency. Dynamics of information processing in a figural transformation task were assessed via time-accuracy functions for children (mean age = 9.5 years), young adults (mean age = 23.7 years), and old adults (mean age = 73.7 years). Corresponding to the two proposed factors, speed and coordination, both sequential and coordinative aspects of complexity were varied. Sequential complexity was manipulated through the number of objects to be checked for transformations; coordinative complexity was manipulated through the number of transformations to be considered simultaneously. Individual time--accuracy operating characteristics were adequately described by exponential functions for all age and complexity levels. Complexity-specific effects confirmed the general expectation of a particularly large age sensitivity of coordinative functions. Proportional adult age effects in the processing time parameter were larger for coordinatively complex than for sequentially complex conditions. For the contrast between children and young adults this was the case only for high coordinative complexity. Results are interpreted in terms of (a) dissociable developmental changes in speed of processing and working memory functioning across the life span and (b) differential effects of coordinative demands in children and old adults.

Time-accuracy functions for determining process and person differences: an application to cognitive aging

A paradigm for the determination of time-accuracy functions (TAFs) for individual participants is introduced for two pairs of tasks differing in cognitive complexity, that is, word scanning vs cued recognition and figural scanning vs figural reasoning. TAFs can be used to test dissociations of cognitive processes beyond scale-related ambiguities of ordinal interactions. The approach is applied to examine the cognitive-aging hypothesis that a single slowing factor can account for interactions between adult age and cognitive task complexity. Twenty young and 20 old adults participated in 17 sessions. Presentation times required for 75, 87.5, and 100% accuracies were determined for each task with a variant of the psychophysical method of limits. Accuracy was fit by negatively accelerated functions of presentation time. State-trace analyses showed that different slowing factors are required for high- and low-complexity tasks. Relations to speed-accuracy and performance-resource functions are discussed.