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Results for “Task demands”

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PubMed1993

Difficulty as a determinant of cardiovascular response: moderating effect of instrumentality in an alleviation paradigm.

Female subjects performed 40 trials of an easy or difficult digit-recognition task while being exposed to intermittent presentations of a noxious noise. Half (high instrumentality) were told that, if they performed well, there was a high chance that they would work without noise in a subsequent trial period. The rest (low instrumentality) were told that, if they performed well, there was a low chance that they would work without noise in the subsequent trial period. Thus, a good performance insured either a high or low probability of alleviating the aversive stimulus. Results indicated that systolic responsiveness was proportional to task demand when the instrumentality of alleviative behavior was high, but low under both task conditions when the instrumentality of alleviative behavior was low. Reaction time and performance data were generally consistent with the view that these effects were due to group differences in task engagement, or 'active coping'. The main findings conceptually replicate and extend results from two previous studies that crossed difficulty and instrumentality manipulations. They also call further into question familiar theoretical conceptions that intimate direct effects of incentive value and perceived control on cardiovascular reactivity.

Adaptation, Psychological↗

PubMed2004

Neural correlates of implicit object identification.

The present study sought to assess neural correlates of implicit identification of objects by means of fMRI, using tasks that require matching of the physical properties of objects. Behavioural data suggests that there is automatic access to object identity when observers attend to a physical property of the form of an object (e.g. the object's orientation) and no evidence for semantic processing when subjects attend to colour. We evaluated whether, in addition to neural areas associated with decisions to specific perceptual properties, areas associated with access to semantic information were activated when tasks demanded processing of the global configuration of pictures. We used two perceptual matching tasks based on the global orientation or on the colour of line drawings. Our results confirmed behavioural data. Activations in the inferior occipital cortex, fusiform and inferior temporal gyri in both tasks (orientation and colour) account for perceptual and structural processing involved in each task. In contrast, activations in the posterior and medial parts of the fusiform gyrus, shown to be involved in explicit semantic judgements, were more pronounced in the orientation-matching task, suggesting that semantic information from the pictures is processed in an implicit way even when not required by the task. Thus, this study suggests that cortical regions usually involved in explicit semantic processing are also activated when implicit processing of objects occurs.

Adult↗

PubMed1998

Task constraints in visual working memory.

This paper examines the nature of visual representations that direct ongoing performance in sensorimotor tasks. Performance of such natural tasks requires relating visual information from different gaze positions. To explore this we used the technique of making task relevant display changes during saccadic eye movements. Subjects copied a pattern of colored blocks on a computer monitor, using the mouse to drag the blocks across the screen. Eye position was monitored using a dual-purkinje eye tracker, and the color of blocks in the pattern was changed at different points in task performance. When the target of the saccade changed color during the saccade, the duration of fixations on the model pattern increased, depending on the point in the task that the change was made. Thus different fixations on the same visual stimulus served a different purpose. The results also indicated that the visual information that is retained across successive fixations depends on moment by moment task demands. This is consistent with previous suggestions that visual representations are limited and task dependent. Changes in blocks in addition to the saccade target led to greater increases in fixation duration. This indicated that some global aspect of the pattern was retained across different fixations. Fixation durations revealed effects of the display changes that were not revealed in perceptual report. This can be understood by distinguishing between processes that operate at different levels of description and different time scales. Our conscious experience of the world may reflect events over a longer time scale than those underlying the substructure of the perceptuo-motor machinery.

Color Perception↗

PubMed2003

Sustained and transient activity during an object-naming task: a mixed blocked and event-related fMRI study.

Cognitive tasks often involve at least two types of processes-sustained processes potentially related to ongoing task demands and transient processes related to the processing of individual items within the task. Using functional magnetic resonance imaging, in conjunction with a mixed-blocked and event-related design, we examined sustained and transient patterns of neural activity during an object-naming task. Subjects were imaged during runs that alternated between control blocks and task blocks. During task blocks, primed and unprimed objects were intermixed and jittered in time. Regions of interest based on separate analyses of sustained and transient activities were tested independently for sustained and transient responses. Three general patterns of results were observed. (1) Some regions exhibited transient responses but little or no sustained response. These regions were widely distributed across the brain. (2) Other regions clearly exhibited both transient and sustained responses. These regions were found primarily in lateral and medial frontal lobes. (3) A few regions exhibited a sustained response but little or no transient responses. These regions were found in the basal ganglia, orbitofrontal lobe, and right lateral frontal lobe. Furthermore, two homotopic regional pairs in the right and left inferior frontal lobe (frontal operculum and inferior frontal cortex) showed a crossover of sustained and transient effects, with greater transient activity in the left and greater sustained activity in the right hemisphere. The asymmetric relationship between sustained and transient responses in prefrontal regions may be an example of task-specific biasing at work.

Adult↗

PubMed1998

Event-based prospective memory and executive control of working memory.

In 5 experiments, the character of concurrent cognitive processing was manipulated during an event-based prospective memory task. High- and low-load conditions that differed only in the difficulty of the concurrent task were tested in each experiment. In Experiments 1 and 2, attention-demanding tasks from the literature on executive control produced decrements in prospective memory. In Experiment 3, attention was divided by different loads of articulatory suppression that did not ultimately lead to decrements in prospective memory. A high-load manipulation of a visuospatial task requiring performance monitoring resulted in worse prospective memory in Experiment 4, whereas in Experiment 5 a visuospatial task with little monitoring did not. Results are discussed in terms of executive functions, such as planning and monitoring, that appear to be critical to successful event-based prospective memory.

Adult↗

PubMed1998

Observational learning and the use of retrieval information during the second and third years.

The authors report 2 cross-sectional studies dealing with observationally derived acquisition of serial and sequentially coordinated activities in children between 12 and 30 months. In Study 1, greater improvements in activity occurred at every age beyond 12 months for modeling than for control groups, demonstrating age-related advances in ability to use modeling in connection with these action classes. However, significant gains did not imply complete reconstruction from memory, which resulted most typically for fewer than 50% of children. Moreover, when sequential tasks were subdivided on the basis of task demands, somewhat greater observationally derived change was found for the class of constrained tasks than for free-standing tasks. Study 2 concentrated on serial task performance and the use of massive retrieval cues in the form of assembled stationary displays, to test the efficacy of such cues in helping children reproduce the serial activities they had observed. Again, children who witnessed modeling were better at reproducing serial assemblies than control-group children. The use of retrieval information, however, was noticeably lacking as late as 22 months, whereas substantial gains were made over the next 6 months. The outcome was supported by exploratory processing results for the 2 ages. Increased use of the cues by 28 months appears to reflect important developments in awareness of the uses to be made of retrieval information, as well as success in its utilization.

Attention↗

PubMed2000

Reactivity and recovery from different types of work measured by catecholamines and cortisol: a systematic literature overview.

OBJECTIVES: To review occupational health, laboratory, and sports literature on neuroendocrine reactivity and recovery from mental, combined mental and physical, or physical tasks. METHODS: A systematic literature search was performed in eight databases. Studies with catecholamines or cortisol as effect variables measured in blood, urine, or saliva were included. RESULTS: After application of inclusion and exclusion criteria, 77 studies from the initial 559 identified were taken into account. In occupational settings it was found that relatively few studies were conclusive about recovery, which formed a contrast with sports research. For reactivity and recovery up to 1 hour after performing the task, half of the studies considered physical tasks and more than two thirds showed incomplete recovery compared with baseline excretion of catecholamines and cortisol. Recovery extending to 3 days after the task was performed was often incomplete for cortisol after combined mentally and physically demanding tasks, and less often after solely mental or physical tasks. This type of recovery was more often incomplete for adrenaline (epinephrine) than for noradrenaline (norepinephrine), which was the case after mental as well as combined mental and physical tasks. CONCLUSIONS: The results from laboratory and sports research may be transferable to some occupations, but more research is needed on the course of recovery relative to health effects in occupational settings.

Biomarkers↗

PubMed1994

Physical fatigue in high and very high frequency manual materials handling: perceived exertion and physiological indicators.

This paper presents the results of a preliminary laboratory study undertaken to determine the perceived exertion and physiological responses of highly trained and experienced workers to high (up to 16 repetitions/min) and very high frequency (above 16 repetitions/min) manual lifting, lowering, and carrying/turning tasks. The results indicate that workers engaged in such highly repetitive and physically demanding tasks may operate at psychophysical workloads that may clearly be considered physically fatiguing and unacceptable according to the current physiological design criteria. In this study subjects performing lifting and lowering tasks, on the average, operated at 57% and 52% of their uphill treadmill aerobic capacity, respectively. For carrying and turning tasks, the average metabolic energy expenditure rate corresponded to 43% of subjects' aerobic capacity. The overall heart rates of the study subjects were 155 beats per minute (bpm) for lifting, 144 bpm for lowering, and 142 bpm for carrying and turning. These physiological responses, when compared with recommended physiological design criteria, are excessively high. The ratings of perceived exertion (RPE) for the shoulder, back, and whole body were highest for lifting (range, 10.20-15.50) and least for carrying and turning (range, 10.30-13.40; carrying and turning activities also included RPE of arms). Generally workers perceived the associated physical exertions as acceptable.

Adult↗

PubMed2005

Motor and non-motor sequence learning in children and adolescents with cerebellar damage.

Cerebellar involvement in motor and non-motor sequence learning was examined with serial reaction time tasks (SRT). Our sample consisted of 8 children and adolescents who had undergone surgical removal of a benign posterior fossa tumor (PFT) during childhood. None of them had undergone chemotherapy or cranial radiation therapy (CRT). Ages ranged from 1-11 years at surgery and 9-17 years at testing. The children were tested not earlier than 2.5 years after surgery (M = 5.9 years), enabling brain plasticity and recovery of functions. Their performance was compared with a matched control sample. The PFT group was not impaired in the implicit learning of sequences, as reflected in their performance in blocks with a repeated sequence, both before and after a random block. However, in the perceptual task, their performance deteriorated more than that of the control group when a random block was introduced, suggesting that it was more difficult for the patients to respond flexibly or change their response set when encountering changing task demands. These results are in line with another study by our group on task switching with the same patients.

Adolescent↗

PubMed1996

Movement-related potential measures of different modes of movement selection in Parkinson's disease.

Movement-related potentials were recorded preceding self-paced voluntary movements in patients with Parkinson's disease and in healthy subjects of the same age group. We compared the Readiness Potential preceding joystick movements in a fixed direction and preceding joystick movements in freely selected directions. In normal subjects the Readiness Potential amplitude was higher preceding freely selected movements than preceding movements in a fixed direction. The Readiness Potential in Parkinson patients failed to be modified by the different modes of movement selection. The modulation of the Readiness Potential by different ways of preparing for movement might be due to the supplementary motor area (SMA) being more strongly engaged by tasks requiring internal control of movements than by tasks that are externally structured. The results suggest that this task-dependent variation of SMA activity is reduced in Parkinson's disease. A failing capacity to adapt SMA activity to different task demands has previously been suggested by evidence from positron emission tomography studies using similar tasks.

Adult↗

PubMed1986

Role of task factors in visual field asymmetries.

Any tachistoscopic study of cerebral hemisphere asymmetry imposes a variety of task demands on the participants, ranging from demands imposed by specific viewing conditions to demands imposed by response output requirements. The present article discusses the role of several task factors that influence processing after the initial reception of the stimulus input, suggests a theoretical rationale for some of the effects of these task factors, and considers implications for future studies of visual laterality. The task factors discussed include both those that are relevant for minimizing artifacts that have nothing to do with hemispheric asymmetry and those that are relevant for interpreting hemispheric asymmetry in terms of specific perceptual and cognitive processes.

Attention↗

PubMed2004

Inconsistency in serial choice decision and motor reaction times dissociate in younger and older adults.

Intraindividual variability (inconsistency) in reaction time (RT) latencies was investigated in a group of younger (M=25.46 years) and older (M=69.29 years) men. Both groups performed 300 trials in 2-, 4-, and 8-choice RT conditions where RTs for decision and motor components of the task were recorded separately. A dissociation was evident in that inconsistency was greater in older adults for decision RTs when task demands relating to the number of choices and fatigue arising from time-on-task were high. For younger persons, a weak trend toward greater inconsistency in motor RTs was evident. The results are consistent with accounts suggesting that inconsistency in neurobiological mechanisms increases with age, and that attentional lapses or fluctuations in executive control contribute to RT inconsistency.

Adult↗

PubMed2000

Representation, space and Hollywood Squares: looking at things that aren't there anymore.

It has been argued that the human cognitive system is capable of using spatial indexes or oculomotor coordinates to relieve working memory load (Ballard, D. H., Hayhoe, M. M., Pook, P. K., & Rao, R. P. N. (1997). Behavioral and Brain Sciences, 20(4), 723), track multiple moving items through occlusion (Scholl, D. J., & Pylyshyn, Z. W. (1999). Cognitive Psychology, 38, 259) or link incompatible cognitive and sensorimotor codes (Bridgeman, B., & Huemer, V. (1998). Consciousness and Cognition, 7, 454). Here we examine the use of such spatial information in memory for semantic information. Previous research has often focused on the role of task demands and the level of automaticity in the encoding of spatial location in memory tasks. We present five experiments where location is irrelevant to the task, and participants' encoding of spatial information is measured implicitly by their looking behavior during recall. In a paradigm developed from Spivey and Geng (Spivey, M. J., & Geng, J. (2000). submitted for publication), participants were presented with pieces of auditory, semantic information as part of an event occurring in one of four regions of a computer screen. In front of a blank grid, they were asked a question relating to one of those facts. Under certain conditions it was found that during the question period participants made significantly more saccades to the empty region of space where the semantic information had been previously presented. Our findings are discussed in relation to previous research on memory and spatial location, the dorsal and ventral streams of the visual system, and the notion of a cognitive-perceptual system using spatial indexes to exploit the stability of the external world.

Adult↗

PubMed2002

Individual inconsistency across measures of inhibition: an investigation of the construct validity of inhibition in older adults.

Inhibition is a central construct to the frontal lobe theory of ageing, yet its construct validity remains unproven. Furthermore, age effects on measures of inhibition are often reported without adequate control for the effects of global slowing on performance. We investigated inhibitory function in older adults in two experiments. In Experiment 1, 49 people with ages between 59 and 86 (mean=70 years 9 months S.D.=7.54) completed four analogues of the Stroop interference paradigm. To control for global slowing and to enable comparisons across all measures, we used a random effects model based on log-transformed response times. Age did not contribute significantly to the model and the estimated correlation between tasks was not significant. In Experiment 2, 33 people with ages between 62 and 86 (mean=73 years 4 months, S.D.=6.57) were compared on two measures of Stroop-like interference which were very similar in surface task demands. Age did not contribute significantly to the model but the estimated correlation between tasks was robust (r=0.714). We conclude that age may make little contribution to inhibitory function independently of other factors such as speed and intelligence. Second, that the level of individual consistency in the performance of measures of inhibition will depend on the similarity of the tasks used.

Age Factors↗

PubMed1989

Effects of age and a divided attention task presented during encoding and retrieval on memory.

The present studies were designed to examine age differences in memory when attention was divided during encoding, retrieval, or at both times. In Experiment 1, Ss studied categorized words while performing a number-monitoring task during encoding, retrieval, or at both times. Older Ss' free recall and clustering performance declined more than that of young Ss when attention was divided at encoding, but there was no similar age interaction when divided attention occurred at retrieval. In Experiment 2, the task demands at retrieval were increased by using a fast-paced, cued-recall task. The results remained unchanged from Experiment 1. Again, an age interaction occurred with divided attention at encoding but not at retrieval. These results were unexpected, given the emphasis in the memory-aging literature on increased difficulty of retrieval by older adults. The findings pose difficulties for limited processing resource views of age differences in memory.

Adult↗

PubMed1996

The effects of task type and task requirements on the dissociation of skin conductance responses and secondary task probe reaction time.

Although task-irrelevant events elicit smaller skin conductance responses (SCRs) than do task-relevant events, secondary task probe reaction time (RT) is often slower during the former. Three experiments (N = 48 in each) examined the effects of task demands, instructions, and stimulus discriminability on this dissociation effect. SCRs were larger to task-relevant stimuli in all experiments regardless of experimental manipulation. Subjects in Experiment 1 counted either all tones of one pitch (high/low group) or longer-than-usual tones of one pitch (longer group). There was more RT slowing during task-irrelevant tones at a 250-ms probe position in the high/low group and at a 150-ms probe position in the longer group. Experiment 2 employed differential Pavlovian conditioning in which the offset of task-relevant stimuli (CS+) coincided with the onset of a shock stimulus. Half the subjects were told which stimulus would be followed by shock (information group), whereas the others received no information (no-information group). Increased RT slowing during CS- was restricted to the no-information group. Experiment 3 employed visual conditioned stimuli that were easy or difficult to discriminate. RT slowing at 4,000 ms was greater during CS+, whereas there was a tendency for more RT slowing during CS- at 150 ms. There was no effect for CS discriminability. The results suggest that during both simple discrimination and during Pavlovian conditioning, task-irrelevant stimuli are more actively processed than task-relevant stimuli within the first 250 ms of stimulus presentation.

Adolescent↗

PubMed2001

Hemispheric asymmetry in categorical versus coordinate visuospatial processing revealed by temporary cortical deactivation.

Kosslyn (1987) proposed that the left hemisphere is better than the right hemisphere at categorical visuospatial processing while the right hemisphere is better than the left hemisphere at coordinate visuospatial processing. In 134 patients, one hemisphere (and then usually the other) was temporarily deactivated by intracarotid injection of sodium amobarbital. After a hemisphere was deactivated, a cognitive test battery was conducted, which included categorical and coordinate visuospatial tasks. Using this technique, the processing capabilities of the intact hemisphere could be determined, thus directly testing Kosslyn's hypothesis regarding hemispheric specialization. Specifically, if the left hemisphere does preferentially process categorical visuospatial relationships, then its deactivation should result in more errors during categorical tasks than right hemisphere deactivation and vise versa for the right hemisphere regarding coordinate tasks. The pattern of results obtained in both categorical and coordinate tasks was consistent with Kosslyn's hypothesis when task difficulty was sufficiently high. However, when task difficulty was low, a left hemispheric processing advantage was found for both types of tasks indicating that: (1) the left hemisphere may be better at "easy" tasks regardless of the type of task and (2) the proposed hemispheric processing asymmetry may only become apparent during sufficiently demanding task conditions. These results may explain why some investigators have failed to find a significant hemispheric processing asymmetry in visuospatial categorical and coordinate tasks.

Adult↗

PubMed1993

Chronic demands and responsivity to challenge.

Certain kinds of arousal in response to challenge situations reflect conditioning that makes one adaptive to task demands. A growing literature implicates chronic stress as a factor degenerating this conditioning. This study investigated the relation between objective occupational demands to which workers were classified for at least 2 years and various indicators of adaptive responsivity to challenge situations. There were consistently significant and negative relations between the occupational exposures and cardiovascular and skin temperature responsivity to the acute challenges administered in the laboratory, the corresponding speed of recovery to baseline after removal of the challenge stimulus, and peripheral catecholamine changes during a work shift.

Adaptation, Physiological↗