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PubMed1997

Allocation of attentional resources during habituation to food cues.

Two experiments were designed to test the hypothesis that habituation to repeated food cues can be inhibited by allocating processing resources to nonfood cues. In two experiments, the salivary response to 10 presentations of lemon yogurt was assessed while subjects engaged in a controlled cognitive search task (demanding attentional resources), an automatic search task (needing fewer attentional resources), or no task. In Experiment 1, the controlled and automatic search tasks differed in the number of memory set items. In Experiment 2, the size of the memory sets was held constant, and individuals were provided practice to stabilize the different search strategies in the task. The automatic search and no task groups habituated to the repeated presentation of food cues in both experiments, but the controlled search group did not. These results support the hypothesis that allocation of attentional resources to external cues can influence the processing of food cues.

Adult↗

PubMed2003

Altering the timing of academic prompts to treat destructive behavior maintained by escape.

Following a functional analysis showing that destructive behavior was reinforced by escape, we altered the aversiveness of task demands by interspersing easy and difficult tasks and by presenting a corrective prompt as an antecedent event the next time a previously failed item was presented; this procedure was compared with one in which the corrective prompt was provided as an immediate consequence. Results of a reversal design showed that the antecedent prompt acted as an establishing operation and reduced destructive behavior to zero.

Adult↗

PubMed2005

The effects of age and task context on Stroop task performance.

In this study, we investigated the impact of age and task context on Stroop task performance, using error scores, response latencies, and process dissociation estimates (e.g., Lindsay & Jacoby, 1994). Across three experiments, the findings showed that although older adults were able to evaluate Stroop task demands and modify their representations of task context in response to this knowledge, they were less able to maintain and update these representations on a trial-by-trial basis in tasks with high stimulus uncertainty or ambiguity. Moreover, although there was no age-related decline in the ability to modulate print color information, older adults were consistently less able to control the activation of conflicting word information. Together, these findings suggest that whereas age differences in the Stroop task may be magnified under conditions that promote transient failures to maintain task context, the primary source of these differences seems to be a more enduring decline in the efficiency of processes that are responsible for suppressing the activation of irrelevant lexical information.

Adolescent↗

PubMed2003

Cigarette smoking and cognitive performance in healthy Swedish adults.

BACKGROUND: The relationship between cigarette smoking and cognitive function was examined in healthy Swedish adults who were participants in the Betula Prospective Cohort Study of Aging, Memory, and Health. SUBJECTS: The data are from those individuals in the Betula study who were self-reported continuous smokers contrasted to those who reported never smoking cigarettes. DESIGN: The dependent variables were cognitive tasks that varied with respect to difficulty and the demand they placed on processing resources. RESULTS: Current smokers performed more poorly than never smokers on the more cognitively demanding tasks; namely, Block Design and free recall. CONCLUSIONS: The findings were interpreted in the light of the assumption that cigarette smoking may exert its greatest deleterious effect on those cognitive tasks that place the heaviest demands on processing resources.

Adult↗

PubMed2005

The effects of local and global processing demands on perception and action.

The line-bisection task, adapted to utilise a wooden rod as the bisection stimulus, has revealed that patients with visuo-spatial neglect may be more accurate at bisection when asked to pick up the rod, compared to pointing to its centre. We recently reported that neurologically intact participants show a similar dissociation on this task-demonstrating a rightward bias when pointing to the centre, which was not present when grasping the rod by the centre. The current paper examined how pointing and grasping responses were affected by adapted rod-bisection tasks that emphasised local or global processing. In Experiment 1, 26 participants completed four rod-bisection tasks. The rods were compound stimuli and the participants directed to focus on either the local or global level. The results demonstrated that when participants focused on the global level, the previous dissociations found for pointing and grasping conditions were evident. However, the perception of centre did change when participants focused on the local level: both the pointing and grasping responses were rightward biased. In Experiment 2, 42 participants completed three bisection tasks which again emphasised either the local or global level, but in different sets of stimuli. The results of this task further support the findings in Experiment 1: the rightward bias in the local-bisection task was again evident and in addition, the global-bisection task resulted in no bias and no difference between the pointing and grasping bisections. These results demonstrate how task demands can similarly affect the pointing and grasping responses, and indicate that local and global processing may be involved in perception/action dissociations on rod bisection.

Adolescent↗

PubMed1999

Aging and selective attention: an issue of complexity or multiple mechanisms?

Previous studies have shown age-associated deficits in selective attention that vary as a function of task demands. The present study was conducted to dissociate the effect of task complexity on age-related performance differences from qualitative differences in cognitive demands. Twenty-four young and 24 older adults were administered two versions of the Stroop Test (Hartley, 1993). The Color-Block version required identifying the color of a box while ignoring the name of a color printed either above or below the box. The Color-Word version required naming the color of a word while ignoring the semantic meaning of the word (a color name). Each version of the task included a two- and four-color choice condition as a manipulation of task complexity. Old and young adults performed comparably on the Color-Block Task, but older adults were significantly impaired on both conditions of the Color-Word Task, particularly in the four-choice condition. Results suggest age-related differences in the distinct attentional processes demanded by each task are not attributable to general slowing.

Adult↗

PubMed1990

Interhemispheric interaction: how do the hemispheres divide and conquer a task?

The present studies investigated how dividing processing between the hemispheres affects task performance. In particular, they examined whether dividing processing between the hemispheres leads to a performance advantage only when task demands exceed a certain threshold. In Experiment 1 processing demands were manipulated by varying the difficulty of the decision process. In the more difficult task, subjects decided as quickly as possible whether two of three letters had the same name (e.g. A a), whereas in the less difficult task they simply decided whether two of the three were physically identical (e.g. A A). As expected, dividing processing between the hemispheres aided performance for the more difficult name-identity task whereas it actually hindered performance for easier physical-identity task. In Experiment 2, subjects made a physical-identity decision about a different stimulus, digits. The pattern of results found in Experiment 1 for the physical-identity task was replicated; interhemispheric processing hindered task performance. These results indicate that the physical characteristics of a stimulus have minimal influence on the extent to which interhemispheric processing aids task performance. In Experiment 3, subjects were required to make more difficult decisions about digits. In one task, they decided whether the sum of two of the three digits was greater than or equal to 10, and in the other they decided if the value of a particular digit was less than either of the other two. Dividing processing between the hemispheres led to faster performance for both tasks, similar to the results for the name-identity condition. In sum, these experiments suggest that when task requirements are demanding, performance is enhanced by distributing processing across the hemispheres.

Adult↗

PubMed1994

The use of pigmentation and shading information in recognising the sex and identities of faces.

An investigation of what can be learned about representational processes in face recognition from the independent and combined effects of inverting and negating facial images is reported. In experiment 1, independent effects of inversion and negation were observed in a task of identifying famous faces. In experiments 2 through 4 the question of whether effects of negation were still obtained when effects due to the reversal of pigmentation in negative images were eliminated was examined. By the use of images of the 3-D surfaces of faces measured by laser, and displays as smooth surfaces devoid of pigmentation, only effects of inversion were obtained reliably, suggesting that the effects observed in experiment 1 arose largely through the inversion of pigmentation values in normal images of faces. The results of experiment 5 suggested that the difference was not due to the different task demands of experiments 2-4 compared with those of experiment 1. When normally pigmented face images were used in a task making similar demands to that of experiment 4, independent effects of inversion and negation were again observed. When a task of sex classification was used in experiments 6 and 7, clear effects of negation as well as inversion were observed on latencies, though not accuracies, of responding. The results are interpreted in terms of the information content of pigmentation relative to shape from shading in different face-classification tasks. The results also reinforce other recent evidence demonstrating the importance of image intensity as well as spatial layout of face 'features'.

Adult↗

PubMed2004

More workload on the central executive of working memory, less attention capture by novel visual distractors: evidence from an fMRI study.

The present study examined the interaction of the central executive in working memory with visual attention. Native Chinese participants were given two versions of a number subtraction task, one of low demand and one of high demand, and were asked to ignore a simultaneously presented peripheral distractor. The distractor could be Chinese or Korean characters, familiar or novel to participants, respectively. Compared with the low-demand subtraction task, brain regions commonly associated with central executive functions, including left middle prefrontal cortex, anterior cingulate cortex, and precentral gyrus/sulcus, were significantly activated in the high-demand task. Critically, there was a significant interaction between distractor type and task demand. Novel distractors captured attention and elicited automatic visual analysis, shown by primary visual cortex activation, only when the subtraction task was of low demand but not when it was of high demand. The results provide confirmatory evidence that the extent to which higher level cognitive resources, specifically, the central executive component of working memory, are absorbed by a cognitive task has an impact upon automatic processing that occurs in response to distracting items.

Adult↗

PubMed2005

Electrophysiological evidence for a natural/artifactual dissociation.

The aim of this work was to test whether the differences usually found between the processing of visual stimuli corresponding to natural and artifactual domains reflect the different ways in which these domains are organized in the brain or are rather due to varying tasks demands. For this purpose, we designed two tasks in which subjects had to classify a series of line drawings. In one task (semantic categorization), the subjects were asked to categorize the stimuli as corresponding either to the natural or the artifactual class, and in the other (gender decision), the subjects had to decide if the names of the stimuli corresponded to either the masculine or the feminine gender. Event-related potentials (ERPs) and reactions times (RTs) were registered during the two tasks. We found both quantitative and topographical differences between ERPs elicited by natural stimuli and those by artifactual stimuli. In the 50- to 200-ms period, ERPs were more positive for the natural stimuli in the categorization task, but more positive for the artifactual stimuli in the gender decision task. In addition, natural stimuli elicited larger P600 and were associated with shorter RTs than artifactual stimuli in the categorization task. These results likely reflect differences concerning the relative difficulty of processing the stimuli of each domain in each task. In the N400 range, in contrast, there were differences between the two domains which were independent of task. In the two tasks, natural and artifactual stimuli elicited ERPs with a different scalp distribution: ERPs were more positive at posterior (parietal and temporal) sites for the natural stimuli and in the frontal areas for the artifactual ones. This finding is consistent with the hypothesis that semantic knowledge associated with natural and artifactual domains is represented in separate subsystems with presumably different anatomical bases.

Adult↗

PubMed2000

Effects of task context and fluctuations of attention on neural activity supporting performance of the stroop task.

The influence of task context and transient fluctuations in attentional control on neural processes supporting performance of the Stroop task was investigated using event-related brain potentials. Task context was manipulated by varying the proportion of congruent and incongruent trials across different blocks of trials, and fluctuations of attentional control were considered by examining differences between trials eliciting faster and slower responses. The amplitudes of the N450, thought to reflect the suppression of a conceptual level processing system, and a temporo-parietal slow wave, thought to index the processing of color information, were greater when trials were mostly congruent in comparison to when trials were mostly incongruent. These findings indicate that the neural systems supporting inhibition and color processing are modulated by task demands. For the N450 the effect of task context interacted with the efficiency of attentional control being present for those trials eliciting faster responses and not for those trials eliciting slower responses. This finding is consistent with those from a growing number of studies indicating that the neural systems supporting attentional control are transient in nature, tending to fluctuate in efficiency over time.

Adult↗

PubMed2001

An experimental study of attention, labelling and memory in people suffering from chronic pain.

Cognitive-behavioural approaches to treatment have become an important part of the clinical management of chronic pain. More recent developments in cognitive-behavioural theory, based on recent developments in the understanding and treatment of health anxiety, have emphasized the importance of catastrophizing appraisals, which drive both attentional processes and behavioural responses, which in turn are believed to be crucial for the maintenance of chronic pain. The experiment conducted here investigated the responses of pain patients (n=39) and controls (n=71) to a behavioural task (prolonged squeezing a dynamometer). Subsequently, the impact of a cognitive task, which fully engaged participants' attention (dichotic listening) was examined. Participants were asked, firstly, to sustain an isometric muscle contraction task (squeezing); secondly, to learn an attentional demanding task (dichotic listening); thirdly, to recall the discomfort experienced in the squeezing task and lastly, to perform both squeezing and dichotic listening at the same time. The squeezing tasks were experimentally manipulated by attaching a more or less negative label ("pain tolerance test" vs. "muscle stamina and strength test"). Patients were found to be less able to sustain prolonged muscle tension than controls, but the effect was not evident once the distracting task was introduced; similar effects were found for discomfort. All participants subsequently recalled the squeezing task as being longer and associated with less discomfort than they had actually recorded it at the time. In the dichotic listening tasks, although patients detected the same number of words overall as controls did, they were less able to focus on the target channel (i.e. they detected more of the words included as distractors on the unattended channel).

Adolescent↗

PubMed1998

Does a photographic cue facilitate false belief performance in subjects with autism?

The posting manipulation, which Mitchell and Lacohée (1991) successfully employed to facilitate false belief (FB) task performance in normally developing 3-year-olds, was employed with subjects with autism. There was no autism-specific impairment on the standard FB task, compared to mental handicap and normal controls: All groups performed poorly, with the autism and normal groups performing significantly worse than chance and the mental handicap group performing at chance. However, a facilitative effect was found on the posting FB task for all subject groups. On the posting task the mental handicap and normal controls groups performed significantly better than chance and the autism group performed at chance. The facilitative effect reached significance for the autism and normal groups. The lack of an autism-specific deficit on the standard task is discussed in relation to the somewhat variable findings of past studies of FB performance in autism. The facilitative effect of the posting manipulation may tell us something about the task demands required to pass a false belief task itself, and suggestions are made for future research to clarify how the facilitative effect operates.

Adolescent↗

PubMed1994

Interpersonal stress and pain behaviors in patients with chronic pain.

This study was designed to empirically evaluate the role of interpersonal stress in eliciting pain behavior. Thirty-four married male patients with chronic back pain (CBP) and their wives participated in a randomized between-groups study examining the effects of 2 interactional conditions (i.e., maritally focused stress interview and neutral talking control task) on subsequent persistence in a physically demanding task and with self-reports of pain. Results indicated that a significantly greater proportion of patients in the stress interview group terminated the physical activity task prematurely, compared with controls. The findings provide some of the first experimental support for the notion that uncomfortable interpersonal interactions may increase the likelihood of subsequent pain behavior in patients with CBP. Clinical implications and directions for future research are addressed.

Adult↗

PubMed2004

Is impaired executive function a single or multidimensional disability?

This study was undertaken to determine if certain logical relations might be found in two pairs of similar executive functioning tasks: (a) Design Fluency and Word Fluency, and (b) the Tinker Toy and Story Telling Tests. Overall, the results were "inconsistent," with there being no meaningful relations found between tests with regard to similarities in task demand, theoretical hierarchical relations, or whether the tasks were verbal or nonverbal (with the exception of a very close relation between Design Fluency and Tinker Toy Test.). Despite the apparent entropy of the findings, they have substantial clinical and theoretical importance given the simultaneously rigid and weak-minded definitions and measures of disexecutive disability in current use.

Adult↗

PubMed2002

Low-back and shoulder complaints among workers with pushing and pulling tasks.

OBJECTIVES: Low-back and shoulder complaints were examined in relation to self-reported and objectively assessed exposure to work-related pushing and pulling. METHODS: Workers from several companies (eg, nursing homes and flower auctions) with pushing and pulling tasks and, as reference, workers without physically demanding tasks were invited to participate. Altogether 829 workers initially received a questionnaire, of whom 459 responded both initially and after 1 year of follow-up. Initially, self-reported exposure to pushing and pulling was assessed by questionnaire. Furthermore, a representative sample of 131 workers was observed at work using TRAC (task recording and analysis on computer) to assess exposure to pushing and pulling objectively. For exposure to pushing and pulling, the workers were classified into a reference group and medium and high exposure groups. Initially and in the follow-up, the 12-month prevalence of low-back and shoulder complaints was assessed. Complaints reported in the follow-up were separately used as dependent variables to calculate prevalence rate ratios (PR) in a Cox's proportional hazard regression analysis. RESULTS: The adjusted PR values were not significant for low-back complaints. For shoulder complaints, both the medium and high exposure groups showed significant adjusted PR values for self-reported exposure and observed duration of pushing and pulling when compared with the reference group (PR range 2.18-4.86). For the observed frequency of pushing and pulling, only the medium exposure group showed a significant PR, of 3.95. CONCLUSIONS: The findings suggest a rather strong relationship between pushing and pulling and shoulder complaints. The evidence for a relationship between pushing and pulling and low-back complaints is limited.

Adult↗

PubMed2003

Distinct neural substrates for visual search amongst spatial versus temporal distractors.

Whether the contribution of the superior parietal cortex (BA7) to attention-demanding tasks is strictly spatial in nature remains unresolved. We used functional magnetic resonance imaging to explore the behavioural and neuroanatomical correlates of non-spatial search for a conjunction of features within a stream of temporally-distracting stimuli. In addition, we compared these data to those from a conventional visuo-spatial search task, performed by the same subjects, in order to determine the specificity of right BA7 activation. Mode of stimulus-distribution (spatial versus temporal) and search type (target defined by a single feature or a conjunction of features) were manipulated in a 2 x 2 factorial design. Behaviourally, the temporal conjunction task was shown to index temporal selective attention. Accuracy of detecting a second target varied with the temporal proximity of two successive targets when subjects searched for a conjunction of features, but not a single feature. The temporal conjunction task activated a network of areas including right superior parietal cortex and bilateral regions of intraparietal sulcus, frontal operculum and putamen. The two latter regions were selectively activated by the attentional demands of the temporal conjunction task when compared directly to the attentional demands of the spatial conjunction task, implicating these regions specifically in selective attention among temporally-distracting stimuli. By comparison, only a very medial region of right BA7 was selectively activated by the spatial conjunction task. The more lateral region of BA7 previously reported by other groups was engaged to a similar degree by both spatial and temporal versions of the conjunction search task.

Adolescent↗

PubMed2000

Cognitive modulation of midbrain function: task-induced reduction of the pupillary light reflex.

The activation of processing resources has widespread effects in the nervous system. A model of pupillary control systems (Steinhauer S.R. , Hakerem G., 1992. The pupillary response in cognitive psychophysiology and schizophrenia. Ann. N.Y. Acad. Sci. 658, 182-204) had predicted that ongoing cognitive activation should result in inhibition of the light reaction at the level of the oculomotor nucleus, n. III, in the midbrain. In this study, modification of parameters of the pupillary reaction to light were examined during varying task demands. The averaged light reaction was recorded from 33 male and female healthy volunteers during the performance of a serial 7 subtraction task and compared to a 'no task' condition. For 13 subjects, an additional verbalization task with little processing demand (add 1) also was presented. Two types of effects were observed. Firstly, the tonic pupil diameter increased from the no task to the easy (add 1) task, and increased further in the more demanding condition (subtract 7). Secondly, the extent of the phasic light reaction was significantly reduced and the latency at the end of the contraction was significantly decreased in the 'subtract 7' condition compared to both the no task and easy conditions (which did not differ from each other). The locus of interference with the light reaction was the Edinger-Westphal complex of the oculomotor nucleus, which is the motor center for the pupillary sphincter muscles. Descending cortical influences inhibited the activity of the Edinger-Westphal complex. Thus, increasing activation had a tonic inhibitory effect on this center, while higher levels of processing complexity produced a separate component of inhibition that interacted with dynamic activation at this midbrain site. It was suggested that the variation in the light reaction is quantitatively responsive to varying processing loads, and may be utilized as a sensitive metric for a wide variety of cognitive operations.

Adolescent↗