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PubMed1998

Influence of individual differences in temporal sensitivity on timing performance.

This research was designed to examine the consistency of individual differences in timing. Subjects were tested initially on a temporal-signal-detection task. In a series of trials, subjects judged whether a stimulus figure was displayed for either 12 s or greater than 12 s. Task performance was used to classify the subjects into groups with high or low temporal sensitivity (d'). Later, the subjects were tested on two classic time-judgment tasks. In a temporal-interference task, subjects reproduced intervals of 8-16 s during which they had rehearsed 0, 3, or 7 digits. Absolute error in time judgments increased linearly as a function of task demands. However, subjects with low temporal sensitivity made more error under all conditions compared with those with high sensitivity. In an isochronous-tapping task, subjects produced a series of 2-s and 5-s intervals. The low-temporal-sensitivity group produced more variable and inaccurate responses than the high-sensitivity group. The results demonstrate cross-situational consistency in timing performance across different tasks, time-judgment methods, and stimulus durations.

Adult↗

PubMed2005

["Persistence" as possible psychogenetic endophenotype].

For some human traits heritability estimates are well known based on results from twin studies. However, the study of connecting these characteristics to candidate genes in the Human Genome has just been started. The main goal of the recently formulated Human Fenom Project is to define "endophenotypes", characteristics that have considerable heritable component, and can be empirically measured with objective tools, standardized across cultures. Based on our recent findings the VNTR polymorphism in the coding region of the dopamine D4 receptor gene is a candidate gene of the "persistence" trait. Individuals carrying the 7-repeat polymorphism of this allele describe themselves as less persistent. In line with these results the 7-repeat polymorphism was associated to the "persistence" trait as measured by the Junior version of the TCI in a psychiatric sample of children diagnosed with ADHD. Based on these findings our main goal was to define an objective, behavioral measure which could be used as an "endophenotype" in genetic association studies. "Persistence" could be related to responsiveness in a reaction time task demanding sustained attention, for example. This hypothesis was tested using a sample of 35 healthy Caucasian subjects, participating in a extended cognitive reaction time task and filling out the TCI personality questionnaire. Non-invasive DNA sampling was used to determine the candidate polymorphism of the DRD4-VNTR. Results using self-report data replicated our previous findings: the 7-repeat polymorphism was significantly associated to lower "persistence" scores. Individual differences of reaction time were compared using the 7-repeat present/absent grouping as well. Results indicate that responses of individuals with the 7-repeat allele were significantly slower and more variable than of those without this candidate allele. Based on self-report and behavioural measures "persistence" trait is a possible endophenotype of psychogenetic associations.

Character↗

PubMed1997

Back pain in the workplace. What you lift or how you lift matters far less than whether you lift or when.

In spite of more than 50 years of concerted effort to diminish task demand, the incidence of compensable back injuries has not wavered. Before we persist for another 50 years in the quest for the "right way to lift," we should consider recent multivariate clinical investigations that suggest alternative approaches. Because task context is at least as important as task content in this regard, it follows that including regional backache under the rubric of "compensable injury" demands reconsideration. Likewise, rather than pursuing the "right way to lift," the more reasonable and humane quest might be for workplaces that are comfortable when we are well and accommodating when we are ill.

Adolescent↗

PubMed1999

Flexible division of labor mediated by social interactions in an insect colony-a simulation model

The primitively eusocial wasp Ropalidia marginata shows an age-based division of labor in which workers allocate tasks according to their relative ages (age ranks). This age polyethism seems quite flexible because in colonies devoid of old workers, young individuals can perform the tasks normally performed by older workers. Social interactions appear to be a plausible mechanism by which workers can assess their relative ages. To explore possible proximate mechanisms that can potentially generate such a flexible, age-based task allocation, the activator-inhibitor model was adapted to the social biology of R. marginata and tested using computer simulations. The model generated a clear age polyethism including the phenomena of precocious foragers in colonies with only young individuals and reverted nurses in colonies consisting of only old individuals. A simple extension of the model to allow the brood:adult ratio to modulate the rates of social interactions, shows how increasing task demands can be met by a decrease in the ages of first performance of, and an increase in the proportions of individuals engaged in, various tasks. These results show how a pattern of division of labor based on relative age can be generated and modulated by social interactions. Copyright 1999 Academic Press.

Journal Article↗

PubMed1994

Escape behavior in task situations: task versus social antecedents.

We designed an investigation to differentiate two types of challenging behaviors occurring in teaching situations: those evoked by task stimuli (i.e., task avoidance), and those evoked by social stimuli present in teaching situations (i.e., social avoidance). Four students with developmental disabilities who exhibited challenging behaviors in teaching situations were exposed to social interaction in a play situation and task demands in a teaching situation. Results indicated that the students exhibited two distinct behavior patterns. Two of the students exhibited a behavior pattern consistent with task avoidance and the other two students exhibited a behavior pattern consistent with social avoidance. Implications concerning task versus social avoidance and the need for more fine-grained analyses of the stimuli associated with escape behavior are discussed.

Autistic Disorder↗

PubMed2000

Microwaves emitted by cellular telephones affect human slow brain potentials.

The influence of electromagnetic fields (EMF) emitted by cellular telephones on preparatory slow brain potentials (SP) was studied in two experiments, about 6 months apart. In the first experiment, a significant decrease of SP was found during exposure to EMF in a complex visual monitoring task (VMT). This effect was replicated in the second experiment. In addition to the VMT, EMF effects on SP were analysed in two further, less demanding tasks: in a simple finger movement task to elicit a Bereitschaftspotential (BP) and in a two-stimulus task to elicit a contingent negative variation (CNV). In comparison to the VMT, no significant main EMF effects were found in BP and CNV tasks. The results accounted for a selective EMF effect on particular aspects of human information processing, but did not indicate any influence on human performance, well-being and health.

Adult↗

PubMed1990

Manual asymmetries during verbal and spatial block design construction.

To examine the effects of cognitive task demands on manual asymmetry, 40 male and 40 female college students were asked to simultaneously construct two replicas of a verbal or spatial block design task, one with each hand. In addition, a verbal and spatial competition task also was performed concurrently with each of the two primary tasks in a dual task paradigm. The spatial primary task elicited increased left-hand use relative to baseline performance, but only in males. An increase in right-hand use was observed during performance of the verbal primary task, again primarily among males. The effects of concurrent cognitive tasks on hand utilization were observed only in subjects performing the verbal primary task, and only when the concurrent task was verbal in nature. Implications for theories of functional cerebral lateralization are discussed.

Adult↗

PubMed2004

Response selection difficulty and asymmetrical costs of switching between tasks and stimuli: no evidence for an exogenous component of task-set reconfiguration.

Four task-switching experiments examined the notion of an exogenous component of task-set reconfiguration (i.e., a process needed to shift task set that is not initiated in the absence of a task-associated figuration stimulus). The authors varied the complexity and familiarity of stimulus-response (SR) mapping rules to produce differentially time-consuming reconfiguration demands. Tasks with more complex or less familiar rules did not display increased switch costs, given that stimulus repetitions were excluded from the analysis. These results do not support the idea of exogenous reconfiguration. Moreover, stimulus repetitions inflated task-switch costs and did so disproportionately for tasks with increased response selection difficulty, thereby demonstrating that insufficient control of the sequence of stimuli may yield results that mimic those predicted by exogenous reconfiguration accounts.

Adult↗

PubMed2003

Articulatory duration in single-word speech production.

Three different speech production paradigms assessed C. T. Kello, D. C. Plaut, and B. MacWhinney's (2000) claim that the characteristics of speech production flexibly vary between staged and cascaded modes depending on task demand. All experiments measured response latencies and durations of single words without and with a response deadline. Experiment 1 used a picture-word interference task; Experiment 2 blocked pictures either by semantic category or by word-initial overlap; and Experiment 3 used a Stroop paradigm. In all cases, systematic effects of semantic and form relatedness were obtained on latencies but not on response durations. These results support the assumption that articulation, as assessed by response duration, is never influenced by central cognitive processes once a response has been initiated.

Cognition↗

PubMed2003

The costs of doing two things at once for young and older adults: talking while walking, finger tapping, and ignoring speech or noise.

Young and older adults provided language samples in response to questions while walking, finger tapping, and ignoring speech or noise. The language samples were scored on 3 dimensions: fluency, complexity, and content. The hypothesis that working memory limitations affect speech production by older adults was tested by comparing baseline samples with those produced while the participants were performing the concurrent tasks. There were baseline differences: Older adults' speech was less fluent and less complex than young adults' speech. Young adults adopted a different strategy in response to the dual-task demands than older adults: They reduced sentence length and grammatical complexity. In contrast, older adults shifted to a reduced speech rate in the dual-task conditions.

Adolescent↗

PubMed2003

[The examination of attentional load theory by Stroop-like task].

Attentional-load theory (Lavie, 1995) states that task load determines whether task-irrelevant stimuli are processed semantically. In three experiments students were asked to perform a Stroop-like task. They named a centrally fixated target color, while ignoring the task-irrelevant stimulus, which was an incompatible, compatible or non-color word. When perceptual load (the number of target-like stimuli adjacent to the target) was increased, the Stroop-like effect was diminished, providing the evidence for early selection. However, when cognitive load (task demands for identical stimuli) was increased, the evidence for late selection was found. These results were inconsistent with the previous hypothesis that both kinds of task load similarly affect the attentional mechanism.

Adult↗

PubMed1984

Nearpoint visual stress: a physiological model.

The nearpoint visual stress theory holds that a tendency for convergence to localize closer than accommodation is intrinsic to the nearpoint visual demands imposed by our culture. A physiological model is presented, suggesting that this effector system mismatch arises from the activation of autonomic reflexes related to stress, vigilant attention and information-processing. Autonomic arousal exerts a cycloplegic-like effect. Excess accommodative effort, which must be exerted to achieve required accommodation, produces a tendency towards overconvergence. The demand for integration of accommodation and convergence, essential for efficient nearpoint function, is thus incompatible with our own physiology, since autonomic arousal is inherent in task demands for attention and mental effort associated with reading. Additionally, autonomic arousal is generated by the high levels of stress pervasive in our society. Various refractive, binocular and accommodative deviations may arise adaptively in order to resolve this mismatch and facilitate efficient nearpoint visual function. These nearpoint stress-induced visual disorders parallel stress-induced systemic illness in that both result from the activation of physiological processes which are inappropriate for the demands and stresses of our society.

Accommodation, Ocular↗

PubMedDate not supplied

Historical factors in the development of ETOH-conditioned place preference.

Three groups of male Sprague-Dawley rats were conditioned with ethanol (ETOH) and water in a Conditioned Place Preference task. To assess the contribution of prior drug/behavioral history on the relative hedonic valence of ETOH, the three groups differed in the task demands and degree of prior ETOH exposure. One group was trained to self-administer 20% w/v ETOH in a home-cage self-administration task using a "Samson sucrose-fading" procedure prior to place conditioning trials (Group SA/CPP). A second group was initially trained in a two-choice ETOH-Saline drug discrimination (DD) task and subsequently conditioned in the place preference paradigm (Group DD/CPP). The third group of rats had no history of drug exposure and were experimentally naive prior to the place learning task (Group NH/CPP). Group SA/CPP developed a significant conditioned place preference; Group DD/CPP failed to demonstrate either a preference or aversion, whereas the Group NH/CPP demonstrated a significant place aversion. Data suggest that both present and past contingencies contribute to the algebraic summation of ETOH's hedonic valences.

Animals↗

PubMed1984

Holistic and analytic modes of processing: the multiple determinants of perceptual analysis.

With the use of the criterion of privileged axes, a set of experimental studies establishes that analytic processing of saturation and brightness, prototypical integral dimensions, does sometimes occur. Still, it is less frequent and less successful than analytic processing of separable dimensions. The studies identify several factors that influence whether or not analytic processing occurs. Among them are the following: (a) stimulus factors, in addition to the choice of dimensions (e.g., the magnitude of dimensional differences); (b) task factors (e.g., the degree to which analytic processing is encouraged by instructions or by implicit task demands, the amount of time available for processing); and (c) subject factors (e.g., the amount of experience that the perceiver has had with the stimuli in tasks that encourage stimulus analysis).

Adolescent↗

PubMed2004

Response selection deficits in melancholic but not nonmelancholic unipolar major depression.

One consistent functional imaging finding from patients with major depression has been abnormality of the anterior cingulate cortex (ACC). Hypoperfusion has been most commonly reported, but some studies suggest relative hyperperfusion is associated with response to somatic treatments. Despite these indications of the possible importance of the ACC in depression there have been relatively few cognitive studies ACC function in patients with major depression. The present study employed a series of reaction time (RT) tasks involving selection with melancholic and nonmelancholic depressed patients, as well as age-matched controls. Fifteen patients with unipolar major depression (7 melancholic, 8 nonmelancholic) and 8 healthy age-matched controls performed a series of response selection tasks (choice RT, spatial Stroop, spatial stimulus-response compatibility (SRC), and a combined Stroop + SRC condition). Reaction time and error data were collected. Melancholic patients were significantly slower than controls on all tasks but were slower than nonmelancholic patients only on the Stroop and Stroop + SRC conditions. Nonmelancholic patients did not differ from the control group on any task. The Stroop task seems crucial in differentiating the two depressive groups, they did not differ on the choice RT or SRC tasks. This may reflect differential task demands, the SRC involved symbolic manipulation that might engage the dorsal ACC and dorsolateral prefrontal cortex (DLPFC) to a greater extent than the, primarily inhibitory, Stroop task which may engage the ventral ACC and orbitofrontal cortex (OFC). This might suggest the melancholic group showed a greater ventral ACC-OFC deficit than the nonmelancholic group, while both groups showed similar dorsal ACC-DLPFC deficit.

Adult↗

PubMed1992

Cigarette smoking and cognitive performance.

While some investigations into the relationship between smoking and cognitive performance have reported that smoking facilitates performance, other research has come to the opposite conclusion. A review of the literature suggests that this variance in results may be due to differences among studies in design (comparing smokers only with deprived smokers rather than with non-smokers) and also to differences in task demands. Therefore, performance of smokers having just smoked, matched smokers deprived for a brief period, and also non-smokers was contrasted on a series of tasks which ranged from repetitive and perceptually-bound tasks to complex, dynamic tasks dependent upon long-term memory. It was found that while cigarette smoking had no negative effect upon performance for simple perceptual tasks, smoking was found to exert measurable negative effects upon performance for more complex information processing tasks.

Adult↗

PubMed2005

Modality pairing effects and the response selection bottleneck.

The present experiment examined the effects of input/output modality pairings on dual-task performance using the psychological refractory period (PRP) procedure. Four groups of participants performed two tasks composed of the same sets of inputs (visual and auditory) and the same sets of outputs (manual and vocal), but with different input/output modality pairings. Whereas modality pairings had only small effects on single-task reaction times, they had large effects on dual-task reaction times. The modality pairing effect cannot stem from differences in the difficulty of stimulus classification or response execution, because these task demands were the same across groups. The effect also does not appear to result from changes in stimulus-response compatibility. The present findings suggest dual-task interference arises not only from postponement of central operations (due to a central bottleneck), but also from a slowing of central operations whose magnitude is sensitive to the input/output modality pairings.

Adolescent↗

PubMed1994

For young jumpers, differences are in the movement's control, not its coordination.

Previous research on the development of jumping has indicated that the coordination of the jump is stable from its inception, but that individual differences lie in the control of the task. The purpose of this study was to examine control in the vertical jump as performed by novice jumpers. Two groups of children who varied in their ability to regulate the takeoff angle were compared on measures of coordination and control. The children's groups were also compared to a group of skilled adults. Both children's groups demonstrated temporal coordination patterns comparable to the adult pattern, though the children were distinguished from the adults on selected spatial (control) measures. The results indicate that a mature pattern of coordination for the jump exists at the earliest stages of the behavior's appearance in the movement repertoire. The novice, however, lacks the ability to precisely control, or tune, the movement to task demands.

Child, Preschool↗