Age-related differences and similarities in dual-task interference.

Differences between younger adults (mean age, 20.7 years) and older adults (mean age, 72.7 years) in dual-task performance were examined in 7 experiments in which the overlap between 2 simple tasks was systematically varied. The results were better fit by a task-switching model in which age was assumed to produce generalized slowing than by a shared-capacity model in which age was assumed to reduce processing resources. The functional architecture of task processing appears the same in younger and older adults. There was no evidence for a specific impairment in the ability of older adults to manage simultaneous tasks. There was evidence for both input and output interference, which may be greater in older adults. (PsycINFO Database Record (c) 2010 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)     

Role of outcome conflict in dual-task interference.

The traditional explanation for dual-task interference is that tasks compete for scarce processing resources. Another possible explanation is that the outcome of the processing required for one task conflicts with the processing required for the other task (e.g., cross talk). To explore the contribution of outcome conflict to task interference, we manipulated the relatedness of the tasks. In Experiment 1, subjects searched concurrently for names of boys in one channel and names of cities in another channel. Responses were significantly delayed when nontarget on one channel belonged to, or was even just related to, the category designated as the target for the other channel. No comparable effects were found when the tasks were performed in isolation. Thus, the difficulty of the individual tasks is not the only determinant of how much they will interfere when combined, and there must be substantial interactions between processes carrying out the two tasks. In Experiment 2 subjects searched one channel for specific target letters and another channel for specific target digits. The nontargets in a channel were either from the same alphanumeric category as the targets for that channel or from the opposite category (i.e., the category of the targets for the other channel). It was found that although between-category search was more efficient than within-category search in single tasks, it was less efficient in dual tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A demonstration of dual-task performance without interference in some older adults.

Highly efficient dual-task processing is demonstrated when reaction time to each of two tasks does not differ between the dual-task situation and the single-task situation. This has been demonstrated reliably in younger adults; nevertheless, the two extant studies of extensive dual-task training did not find evidence for it in any elderly adult. The origins of age-related differences after training were explored in a study in which the stimuli for the two tasks were perfectly redundant although two distinct responses were required. The dual-task situation thus greatly reduced the demands of stimulus categorization while still requiring two response selections and two response executions. After only limited training 8 of 8 younger adults and 5 of 8 older adults showed performance consistent with highly efficient processing. Three older adults failed to show this even after 12 training sessions. The results implicate stimulus categorization more than response selection as an important locus of inefficient dual-task processing, particularly for older adults. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Locus of the single-channel bottleneck in dual-task interference.

Two experiments used the locus-of-cognitive-slack method to determine whether dual-task interference occurs before or after the response selection stage. The experiments used the overlapping tasks paradigm, in which 2 signals, each requiring a different speeded choice response, are presented in rapid succession. In Exp 1, stimulus–response (S–R) compatibility was manipulated by varying whether Task 2 stimuli were mapped onto their responses by a rule or arbitrarily. Compatibility effects were additive with the effects of degree of task overlap, manipulated by varying the stimulus onset asynchrony between the signals. Exp 2 examined 2 additional forms of S–R compatibility: symbolic compatibility (arrows vs letters) and spatial compatibility (the "Simon" effect). Effects of symbolic compatibility were additive with effects of degree of task overlap, whereas the effects of spatial compatibility and degree of task overlap were underadditive. It is argued that only a central-bottleneck model provides a consistent account of these results. The nature of the central bottleneck is considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

French immersion and hemispheric language processing: A dual-task study.

32 right-handed high school boys in early or late French immersion programs and 16 nonimmersion, unilingual high school boys performed verbal tasks (reading aloud and identifying pictures) in English and French while finger-tapping with the index finger of their left or right hand. Disruption scores were calculated and used to infer contralateral hemispheric involvement. All Ss showed significantly greater disruption with right-hand tapping, indicating high levels of left hemisphere involvement. Results confirm that early and late bilinguals do not differ from each other or from unilinguals in the hemispheric processing of language. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Network interference and mental multiplication.

Investigated predictions of the network-interference theory in the retrieval of multiplication facts in 2 experiments involving 27 undergraduates (aged 19–30 yrs). Ss were tested with 36 interference or practice multiplication problems. Results indicate that retrieval of a product via one problem increased the probability that this product will be retrieved in error to another problem later. The effect of retrieval priming on error patterns was problem-specific, occurring when there were relatively strong associations between a problem and the false answers that were primed. Correct retrieval times for specific problems were increased or decreased by manipulating the activation levels of strong false associates through correct retrievals via other problems. It is argued that single-digit multiplication problems access a network structure of candidate answers and that different problems can overlap in the network substructures they activate. A model of network interference is proposed in which activation is distributed among candidate answers as a multiplicative function of associative and node strengths. Predictions derived from the hypothesis that adults' production of simple number combinations is governed substantially by procedural operations were not confirmed. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Executive control of visual attention in dual-task situations.

A theory of executive control is presented that proposes that executive processes control subordinate processes by manipulating their parameters, reconfiguring them to respond in accord with the current task set. It adopts C. Bundesen's (1990) theory of visual attention (TVA) and R. M. Nosofsky and T. J. Palmeri's (1997) exemplar-based random walk (EBRW) as the theory of subordinate processes. It assumes that a task set is a set of TVA and EBRW parameters sufficient to perform a task and that set switching involves changing those parameters. The theory solves 2 computational problems that emerge in dual-task situations. the binding problem and the serial order problem. It can perform dual tasks in series or in parallel but prefers the serial strategy because it is faster and it solves the binding problem naturally. The theory accounts for concurrence cost, set-switching cost, crosstalk between tasks, and the modulation of crosstalk by task set. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The locus of dual-task interference: Psychological refractory effects on movement-related brain potentials.

Sought to measure the motor potentials for each of 2 concurrent tasks and to use these measurements to identify the locus of dual-task interference. Lateralized readiness potentials (LRPs) were measured in the psychological refractory period paradigm, in which a separate response is required to each of 2 successive signals. As the interval between the signals decreased, the 2 reaction time (RT) tasks increasingly overlapped and the 2nd RT was prolonged. The LRP for the 2nd task was also delayed but maintained a constant temporal relation with the 2nd RT and sometimes preceded the 1st-task RT. The results indicate that (1) independent measures of the LRP can be obtained for each of 2 concurrent tasks, (2) slowing of the 2nd task was caused by a delay in processes that precede LRP onset, and (3) the 1st task may cease to interfere with the 2nd considerably before producing an overt response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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. (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)     

Attention, gaze shifting, and dual-task interference from phonological encoding in spoken word planning.

Controversy exists about whether dual-task interference from word planning reflects structural bottleneck or attentional control factors. Here, participants named pictures whose names could or could not be phonologically prepared, and they manually responded to arrows presented away from (Experiment 1), or superimposed onto, the pictures (Experiments 2 and 3); or they responded to tones (Experiment 4). Pictures and arrows/tones were presented at stimulus onset asynchronies of 0, 300, and 1,000 ms. Earlier research showed that vocal responding hampers auditory perception, which predicts earlier shifts of attention to the tones than to the arrows. Word planning yielded dual-task interference. Phonological preparation reduced the latencies of picture naming and gaze shifting. The preparation benefit was propagated into the latencies of the manual responses to the arrows but not to the tones. The malleability of the interference supports the attentional control account. This conclusion was corroborated by computer simulations showing that an extension of WEAVER++ (A. Roelofs, 2003) with assumptions about the attentional control of tasks quantitatively accounts for the latencies of vocal responding, gaze shifting, and manual responding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A dual-task analysis of resource allocation in dysthymia and anhedonia.

Research has shown dysthymic individuals to be hyporesponsive at various stages of information processing, yet it is not clear whether dysthymics are deficient in the amount of available attentional resources for information processing or, instead, in the allocation of those resources. To distinguish between these possibilities, dysthymics were compared to anhedonic and normal control Ss during the performance of memory tasks, under conditions of varying task priority and difficulty. Although there were no performance differences, dysthymics and anhedonics exhibited a consistently smaller P300 component of the event-related potential. Furthermore, P300 results indicated that dysthymics and anhedonics responded differently from controls to variations in task demands. Thus, although evidence was obtained for group differences in both resource capacity and resource allocation strategy, the overall pattern of results is interpreted as favoring the latter. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A central capacity sharing model of dual-task performance.

The authors present the central capacity sharing (CCS) model and derive equations describing its behaviors to explain results from dual-task situations. The predictions of the CCS model are contrasted with those of the central bottleneck model. The CCS model predicts all of the hallmark effects of the psychological refractory period (PRP) paradigm: -1 slope of the PRP effect at short stimulus onset asynchronies (SOAs), underadditivity of precentral Task 2 manipulations, additivity of central or postcentral Task 2 manipulations with SOA, and carry forward to Task 2 of Task 1 precentral or central manipulations at short SOAs. The CCS model also predicts that Task 1 response times increase with decreasing SOA. The model is a viable alternative to the central bottleneck model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relationship of client abuse with locus of control and gender: A longitudinal study in mental retardation facilities.

Direct-care workers (158 women and 154 men) participated in a study of aggressive work behavior. Employees completed J. B. Rotter's (1966) Locus of Control Scale. Client abuse data were collected over a 2-yr period. Individuals reporting higher levels of external locus of control and men were more likely to emit aggressive behavior than were people reporting lower levels of external locus of control and women. Results supported the hypotheses and suggested that individual and group differences may be useful in understanding maladaptive, aggressive work behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A study of the clinical test of sensory interaction and balance

BACKGROUND AND PURPOSE: The ability to maintain an upright position during quiet standing is a useful motor skill. The Clinical Test of Sensory Interaction and Balance is an inexpensive, easily administered test that provides information about the ability to stand upright under several sensory conditions. SUBJECTS: Three groups of neurologically asymptomatic (AS) adults, divided by age into younger, middle-aged, and older groups, participated in the study. A fourth group comprised subjects diagnosed with vestibular disorders. METHODS: Timed performances under six different conditions were compared across groups. RESULTS: Subjects with vestibular disorders were significantly impaired on performance when compared with age-matched AS subjects. Older AS and vestibularly impaired subjects had greater variation in their scores than did younger AS subjects. CONCLUSION AND DISCUSSION: This test is a useful screening tool for examining static standing balance.     

Neural mechanisms of interference control underlie the relationship between fluid intelligence and working memory span.

Fluid intelligence (gF) and working memory (WM) span predict success in demanding cognitive situations. Recent studies show that much of the variance in gF and WM span is shared, suggesting common neural mechanisms. This study provides a direct investigation of the degree to which shared variance in gF and WM span can be explained by neural mechanisms of interference control. The authors measured performance and functional magnetic resonance imaging activity in 102 participants during the n-back WM task, focusing on the selective activation effects associated with high-interference lure trials. Brain activity on these trials was correlated with gF, WM span, and task performance in core brain regions linked to WM and executive control, including bilateral dorsolateral prefrontal cortex (middle frontal gyrus; BA9) and parietal cortex (inferior parietal cortex; BA 40/7). Interference-related performance and interference-related activity accounted for a significant proportion of the shared variance in gF and WM span. Path analyses indicate that interference control activity may affect gF through a common set of processes that also influence WM span. These results suggest that individual differences in interference-control mechanisms are important for understanding the relationship between gF and WM span. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

A mental practice superiority effect: Less retroactive interference and more transfer than physical practice.

Two experiments explored the benefits to retention and transfer conferred by mental practice. During familiarization, participants typed 4-digit numbers and took an immediate typing test on both old and new numbers. Participants then typed old 4-digit numbers, either physically or mentally, with either a different response configuration or the opposite hand from that used during familiarization. On a delayed test, participants physically typed both old and new numbers with the same response configuration and hand used during familiarization. Mental practice led to less retroactive interference and more transfer than did physical practice, supporting the hypothesis that mental practice strengthens an abstract representation that does not involve specific effectors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thyroid hormone control of thermogenesis and energy balance

An extensive analysis was made of receptor specificity and gene usage in the neutralising antibody (mAb) and Class II-restricted T cell responses to influenza haemagglutinin (HA) following natural infection of MHC (H-2(k) or H-2(d)) congenic mice with X31 virus (H3N2 subtype). Despite the diversity of available antigenic sites on the HA1 subunit, there was striking immunodominance in the mAb response as deduced by sequencing the HA genes of escape mutants and the corresponding antibody H and L chain gene rearrangements. Similarly, Class II restricted T cell responses of individual donors focused on a single antigenic site, or immunodominant peptide; and PCR sequence analysis of T cell receptor (alpha beta) gene usage indicated that T cell memory was derived from a single progenitor cell. Focusing of the immune repertoire to limited regions of the HA molecule during a primary viral infection may be a significant factor in immune pressure for antigenic variation.