Manipulated Task Difficulty Research Articles

The Presence of a Therapy Dog Results in Improved Object Recognition Performance in Preschool Children

ABSTRACTThe purpose of this study was to determine whether the presence of a dog would have an impact on object recognition memory performance of preschool children. This work represents an extension of previous research which found that preschoolers require fewer instructional prompts to complete this type of memory task when in the presence of a dog. If children require fewer instructional prompts it is possible that they are better able to focus on the task itself and as a result, improved memory performance is likely. Because the earlier experiment utilized a very simple version of the task that was readily completed by the preschool children, the overall performance data were at ceiling. The current study, involving 20 preschool children, included a manipulation of task difficulty through varying the number of distracters (one versus four) present at test. Increasing the number of distractors in a simple recognition task is known to make that task more challenging, and thus performance was expected to be slower and less accurate in the four distracter conditions relative to the one-distracter conditions. The collaborators in the study were either a therapy dog or a human. A two-way repeated measures design was used such that each child served as his/her own control and was tested in each of four separate conditions: dog present (one and four distracters) and human present (one and four distracters). The results showed that the preschool children performed the object recognition task faster and more accurately in the presence of the therapy dog relative to a human and also in the one-distracter versus four-distracter condition. The authors conclude that these effects result from increased focus and/or motivation resulting from the presence of the dog.

J15 Dual task performance in Huntington's disease: comparing choice reaction time tasks

Background Huntington9s disease (HD) is associated with difficulty performing concurrent tasks, an ability which is a requirement of everyday activities and of potential functional significance in HD. Aims We compared dual task performance in HD and healthy controls using choice reaction time (CRT) with digit span tasks. We manipulated task difficulty and tested for interactions between difficulty level and group which would indicate differential effects of difficulty on dual tasking in HD. Methods/techniques 14 participants in the early stages of HD and 14 controls performed two series of dual tasks. Series one paired simple CRT with digit span forward; series two paired complex CRT with digit span backward. Each of the tasks within each series had easy and hard conditions. In the simple CRT easy condition participants viewed single letters and had to press a key labelled Yes if the letter was X or Z or No for other letters. For the hard condition, there were four target letters (X, Z, O, Y); participants had to repeat four (easy) or five (hard) digits forward. The complex CRT task comprised 3×3 matrices of Xs and Os. Participants had to respond whether three Xs (easy) or three Xs or three Os (hard) appeared in a row. Complex CRT was paired with three (easy) or four (hard) digit span backward. Task order was counterbalanced for series, but within series it was proceeded from easier to harder pairs. Measures were speed and accuracy. Results/outcome Participants with HD were slower and less accurate, a finding that, surprisingly, was more profound in the simple CRT with digit span forward than in the more difficult conditions. Error rates were higher in HD when the simple CRT tasks were performed with the hard digit span forward, suggesting that task difficulty may affect cognitive load in HD. Conclusion Simple CRT with digit span forward appeared to be more affected in HD than complex CRT with digit span backwards, suggesting that impaired automaticity may underlie attentional deficits in HD.

Movement control in older adults: Does old age mean middle of the road?

Old age is associated with poorer movement skill, as indexed by reduced speed and accuracy. Nevertheless, reductions in speed and accuracy can also reflect compensation as well as deficit. We used a manual tracing and a driving task to identify generalized spatial and temporal compensations and deficits associated with old age. In Experiment 1, participants used a hand-held stylus to trace a path. In Experiment 2, participants steered along paths in a virtual reality driving simulator. In both experiments, participants were required to stay within the boundaries while we manipulated task difficulty by changing path width or movement speed. The older group showed worse performance in the highly constrained conditions. Corner cutting effectively reduces the curvature of bends but yields a greater risk of error (i.e., clipping the path or road edge). Corner cutting is thus less risky on wider paths, and we found that corner cutting increased for both age groups in both tasks when paths were wider. Crucially, we observed a greater degree of corner cutting in the young group compared with the old, suggesting the old group compensated for decreased motor skill with "middle-of-the-road" behavior. Enforcing increased speed caused all participants to increase corner cutting. Thus, older participants showed spatial compensation for decreased skill by biasing their position toward the middle of the path in both a manual and steering task. External constraints (narrow paths and fast speeds) prevented this strategy and revealed age-related declines in skills central to manual control and driving.

Same Modulation but Different Starting Points: Performance Modulates Age Differences in Inferior Frontal Cortex Activity during Word-Retrieval

The neural basis of word-retrieval deficits in normal aging has rarely been assessed and the few previous functional imaging studies found enhanced activity in right prefrontal areas in healthy older compared to younger adults. However, more pronounced right prefrontal recruitment has primarily been observed during challenging task conditions. Moreover, increased task difficulty may result in enhanced activity in the ventral inferior frontal gyrus (vIFG) bilaterally in younger participants as well. Thus, the question arises whether increased activity in older participants represents an age-related phenomenon or reflects task difficulty effects. In the present study, we manipulated task difficulty during overt semantic and phonemic word-generation and used functional magnetic resonance imaging to assess activity patterns in the vIFG in healthy younger and older adults (N = 16/group; mean age: 24 vs. 69 years). Both groups produced fewer correct responses during the more difficult task conditions. Overall, older participants produced fewer correct responses and showed more pronounced task-related activity in the right vIFG. However, increased activity during the more difficult conditions was found in both groups. Absolute degree of activity was correlated with performance across groups, tasks and difficulty levels. Activity modulation (difficult vs. easy conditions) was correlated with the respective drop in performance across groups and tasks. In conclusion, vIFG activity levels and modulation of activity were mediated by performance accuracy in a similar way in both groups. Group differences in the right vIFG activity were explained by performance accuracy which needs to be considered in future functional imaging studies of healthy and pathological aging.

Using Adaptive Difficulty to Optimize Videogame-Based Training Performance: The Moderating Role of Personality

While videogames can easily be tailored to provide “adaptive training,” little research exists examining whether this benefit enhances training outcomes. The current study investigated three task difficulty manipulations and the moderating role of personality. Participants engaged in six 7-minute missions in a videogame-based training task. Openness to experience and neuroticism, but not conscientiousness, interacted with task difficulty condition such that trainees higher in these traits performed better over the course of training in the adaptive condition. These results suggest that adaptive training can result in the greatest performance improvement when the trainee's personality is suited to the instructional environment.

Using functional transcranial Doppler ultrasonography to assess language lateralisation: Influence of task and difficulty level

Language is lateralised to the left hemisphere in most people, but it is unclear whether the same degree and direction of lateralisation is found for all verbal tasks and whether laterality is affected by task difficulty. We used functional transcranial Doppler ultrasonography (fTCD) to assess the lateralisation of language processing in 27 young adults using three tasks: word generation (WG), auditory naming (AN), and picture story (PS). WG and AN are active tasks requiring behavioural responses whereas PS is a passive task that involves listening to an auditory story accompanied by pictures. We also examined the effect of task difficulty by a post hoc behavioural categorisation of trials in the WG task and a word frequency manipulation in the AN task. fTCD was used to measure task-dependent blood flow velocity changes in the left and right middle cerebral arteries. All of these tasks were significantly left lateralised: WG, 77% of individuals left, 5% right; AN, 72% left: 4% right; PS, 56% left: 0% right. There were significant positive relationships between WG and AN (r=0.56) as well as AN and PS (r=.76) but not WG and PS (r = −0.22). The task difficulty manipulation affected accuracy in both WG and AN tasks, as well as reaction time in the AN task, but did not significantly influence laterality indices in either task. It is concluded that verbal tasks are not interchangeable when assessing cerebral lateralisation, but that differences between tasks are not a consequence of task difficulty.

Slowing Down after a Mild Traumatic Brain Injury: A Strategy to Improve Cognitive Task Performance?

Long-term persistent attention and memory difficulties following a mild traumatic brain injury (TBI) often go undetected on standard neuropsychological tests, despite complaints by mild TBI individuals. We conducted a visual Repetition Detection working memory task to digits, in which we manipulated task difficulty by increasing cognitive load, to identify subtle deficits long after a mild TBI. Twenty-six undergraduate students with a self-report of one mild TBI, which occurred at least 6 months prior, and 31 non-head-injured controls took part in the study. Participants were not informed until study completion that the study's purpose was to examine cognitive changes following a mild TBI, to reduce the influence of "diagnosis threat" on performance. Neuropsychological tasks did not differentiate the groups, though mild TBI participants reported higher state anxiety levels. On our working memory task, the mild TBI group took significantly longer to accurately detect repeated targets on our task, suggesting that slowed information processing is a long-term consequence of mild TBI. Accuracy was comparable in the low-load condition and, unexpectedly, mild TBI performance surpassed that of controls in the high-load condition. Temporal analysis of target identification suggested a strategy difference between groups: mild TBI participants made a significantly greater number of accurate responses following the target's offset, and significantly fewer erroneous distracter responses prior to target onset, compared with controls. Results suggest that long after a mild TBI, high-functioning young adults invoke a strategy of delaying their identification of targets in order to maintain, and facilitate, accuracy on cognitively demanding tasks.

Attentional modulation in visual cortex is modified during perceptual learning

Practicing a visual task commonly results in improved performance. Often the improvement does not transfer well to a new retinal location, suggesting that it is mediated by changes occurring in early visual cortex, and indeed neuroimaging and neurophysiological studies both demonstrate that perceptual learning is associated with altered activity in visual cortex. Theoretical treatments tend to invoke neuroplasticity that refines early sensory processing. An alternative possibility is that performance is improved because of an altered attentional strategy and that the changes in early visual areas reflect locally altered top-down attentional modulation. To test this idea, we have used functional MRI to examine changes in attentional modulation in visual cortex while participants learn an orientation discrimination task. By examining activity in visual cortex during the preparatory period when the participant has been cued to attend to an upcoming stimulus, we isolated the top-down modulatory signal received by the visual cortex. We show that this signal changes as learning progresses, possibly reflecting gradual automation of the task. By manipulating task difficulty, we show that the change mirrors performance, occurring most quickly for easier stimuli. The effects were seen only at the retinal locus of the stimulus, ruling out a generalized change in alertness. The results suggest that spatial attention changes during perceptual learning and that this may account for some of the concomitant changes seen in visual cortex.

Controlling the spotlight of attention: Visual span size and flexibility in schizophrenia

The current study investigated the size and flexible control of visual span among patients with schizophrenia during visual search performance. Visual span is the region of the visual field from which one extracts information during a single eye fixation, and a larger visual span size is linked to more efficient search performance. Therefore, a reduced visual span may explain patients’ impaired performance on search tasks. The gaze-contingent moving window paradigm was used to estimate the visual span size of patients and healthy participants while they performed two different search tasks. In addition, changes in visual span size were measured as a function of two manipulations of task difficulty: target–distractor similarity and stimulus familiarity. Patients with schizophrenia searched more slowly across both tasks and conditions. Patients also demonstrated smaller visual span sizes on the easier search condition in each task. Moreover, healthy controls’ visual span size increased as target discriminability or distractor familiarity increased. This modulation of visual span size, however, was reduced or not observed among patients. The implications of the present findings, with regard to previously reported visual search deficits, and other functional and structural abnormalities associated with schizophrenia, are discussed.

The Fitts task reveals impairments in planning and online control of movement in Friedreich ataxia: reduced cerebellar-cortico connectivity?

Friedreich ataxia (FRDA) is the most common of the inherited ataxias. We have suggested that people with FRDA may have impairment in cognitive and/or psychomotor capacity either due to disturbance of projections of the cerebellum to the cortex, direct cortical pathology or perhaps both. To further explore this possibility, we used a movement task incorporating Fitts' Law, a robust description of the relationship between movement time and accuracy in goal-directed aiming movements. By manipulating task difficulty, according to target size and distance, we were able to quantify processes related to motor planning in 10 individuals with FRDA and 10 matched control participants. Compared to control participants, people with FRDA were significantly disadvantaged in terms of movement time to targets with an increasing index of difficulty. Successful completion of this task requires both preplanning of movement and online error detection and correction. The cerebellum and its connections to the frontal cortex via cerebro-ponto-cerebello-thalamo-cerebral loops are fundamental to both processes. These results lend further support to our contention that in FRDA these loops are impaired, reflecting a failure to access prefrontal/anterior regions necessary for effective management of preplanning of movement and online error correction.

Attentional modulation in visual cortex is modified during perceptual learning

Practicing a visual task commonly results in improved performance. Often the improvement does not transfer well to a new retinal location, suggesting that it is mediated by changes occurring in early visual cortex, and indeed neuroimaging and neurophysiological studies both demonstrate that perceptual learning is associated with altered activity in visual cortex. Theoretical treatments tend to invoke neuroplasticity that refines early sensory processing. An alternative possibility is that performance is improved because of an altered attentional strategy and that the changes in early visual areas reflect locally altered top-down attentional modulation. To test this idea, we have used functional MRI to examine changes in attentional modulation in visual cortex while participants learn an orientation discrimination task. By examining activity in visual cortex during the preparatory period when the participant has been cued to attend to an upcoming stimulus, we isolated the top-down modulatory signal received by the visual cortex. We show that this signal changes as learning progresses, possibly reflecting gradual automation of the task. By manipulating task difficulty, we show that the change mirrors performance, occurring most quickly for easier stimuli. The effects were seen only at the retinal locus of the stimulus, ruling out a generalized change in alertness. The results suggest that spatial attention changes during perceptual learning and that this may account for some of the concomitant changes seen in visual cortex.

How affective states, task difficulty, and self-concepts influence the formation and consequences of performance expectancies

Positive versus negative affective states are associated with the use of broad versus specific knowledge structures. We predicted that specific self-concepts and task difficulty would affect performance expectancies only for individuals in a negative mood; for individuals in a positive mood, only the general self-concept, but not task difficulty, would affect performance expectancies. In an experiment, we manipulated task difficulty and mood, and we assessed self-concepts, performance expectancies, and task performance. The expected interactions for the formation of performance expectancies (mood×general self-concept, mood×specific self-concept, mood×difficulty) were found. Concerning the consequences of performance expectancies, we predicted that expectancies would affect actual performance only if the task was difficult and if task difficulty was taken into account when the expectancy is generated. This hypothesis was supported: The relationship between performance expectancies and actual performance was significant only for difficult tasks and given negative mood.

Activations of Human Auditory Cortex During Visual and Auditory Selective Attention Tasks with Varying Difficulty

The present study was designed to directly test the hypothesis that suppression of activations to task-irrelevant sounds contributes to the attention-related modulations of auditory cortex (AC) activations observed in previous fMRI studies. Subjects selectively attended to auditory (broadband noise bursts with pitch) or visual (Gabor gratings) asynchronous fast-rate stimulus streams concurrently presented to left-ear, right-ear, above-fixation, or below-fixation. Auditory and visual task difficulty was parametrically manipulated in three levels. Behavioral data obtained during fMRI indicated that subjects achieved acceptable performance levels in all tasks and that the task-difficulty manipulation was effective. Consistent with previous studies, AC activations strongly depended on the direction of attention. AC activations to sounds were higher during auditory than during visual tasks and AC activations were higher in the hemisphere contralateral to the attended ear. However, the effects of task difficulty on AC activations were weak or non-existent. In particular, increasing task difficulty was not associated with a systematic decrease of AC activations in areas that were modulated by attention. These results suggest that suppression of AC activations to task-irrelevant sounds is likely to be small or negligible as compared with the strong activation enhancements observed in fMRI during active auditory tasks.

Using Video Animation to Assess Mobility in Older Adults

Although the importance of the context of task performance in the assessment of mobility in older adults is generally understood, there is little empirical evidence that demonstrates how sensitive older adults are to subtle changes in task demands. Thus, we developed a novel approach to examine this issue. We collected item response data to 81 animated video clips, where various mobility-related tasks were modified in a systematic fashion to manipulate task difficulty. The participants (N = 234), 166 women and 68 men, had an average age of 81.9 years and a variety of comorbidities. Histograms of item responses revealed dramatic and systematic effects on older adults' self-reported ability when varying walking speed, use of a handrail during ascent and descent of stairs, walking at different speeds outdoors over uneven terrain, and carrying an object. For example, there was almost a threefold increase in reporting the inability to walk at the fast speed compared with the slow speed for a minute or less, and twice as many participants reported the inability to walk at the fast speed outdoors over uneven terrain compared with indoors. The data provide clear evidence that varying the contextual features and demands of a simple task such as stair climbing has a significant impact on older adults' self-reporting of ability related to mobility. More work is needed on the psychometric properties of such assessments and to determine if this methodology has conceptual and clinical relevance in studying mobility disability.

A kinematic analysis of visually-guided movement in Williams syndrome

Previous studies have reported that people with the neurodevelopmental disorder Williams syndrome exhibit difficulties with visuomotor control. In the current study, we examined the extent to which visuomotor deficits were associated with movement planning or feedback-based on-line control. We used a variant of the Fitts' reciprocal aiming task on a computerized touchscreen in adults with WS, IQ-matched individuals with Down syndrome (DS), and typically developing controls. By manipulating task difficulty both as a function of target size and amplitude, we were able to vary the requirements for accuracy to examine processes associated with dorsal visual stream and cerebellar functioning. Although a greater increase in movement time as a function of task difficulty was observed in the two clinical groups with WS and DS, greater magnitude in the late kinematic components of movement—specifically, time after peak velocity—was revealed in the WS group during increased demands for accuracy. In contrast, the DS group showed a greater speed-accuracy trade-off with significantly reduced and more variable endpoint accuracy, which may be associated with cerebellar deficits. In addition, the WS group spent more time stationary in the target when task-related features reflected a higher level of difficulty, suggestive of specific deficits in movement planning. Our results indicate that the visuomotor coordination deficits in WS may reflect known impairments of the dorsal stream, but may also indicate a role for the cerebellum in dynamic feed-forward motor control.

Effort Mobilization when the Self is Involved: Some Lessons from the Cardiovascular System

In this article it is proposed that the principles of motivational intensity theory ( Brehm & Self, 1989 ) apply to effort mobilization for challenges with consequences for performers’ self-esteem and self-definition (i.e., self-involvement). Accordingly, involvement of the self makes success important and thus justifies the mobilization of high resources. However, up to this level of maximally justified resources, actual effort is mobilized in correspondence to subjective task difficulty as long as success is possible. We report a series of experimental studies that have operationalized effort intensity as cardiovascular reactivity during task performance and used multiple manipulations of self-involvement (social evaluation, self-awareness, ego involvement, personal goals) and task difficulty. The empirical evidence clearly supports the idea that the principles of motivational intensity theory apply to performance conditions that have direct consequences for self-definition and self-esteem and challenges a number of other theoretical accounts.

Team Performance as a Function of Task Difficulty in a Computer Game

Specialized military field training can be expensive, time-consuming and dangerous. Computer games provide a safe, cost effective, and controlled method for geographically dispersed military units to develop decision-making skills while rehearsing a specific task. Military units can rehearse building clearing, search and rescue, or navigation using computer games. The purpose of this study was to investigate the relationship between task difficulty and team task performance during a team search task using a modified version of a popular video game. Results showed that task difficulty decreased the speed with which the task was completed. The present research demonstrates successful manipulation of task difficulty in a virtual environment. There were performance differences based on the sex composition of the teams. Same sex teams performed better than opposite sex teams. This research suggests researchers and trainers can modify game characteristics, such as task difficulty, to design and implement training programs within the military.

Magnitude of negative priming varies with conceptual task difficulty: Attentional resources are involved in episodic retrieval processes

In a variant of the negative priming (NP) procedure, the larger of two presented animals is to be named in each trial. Eight animals of different sizes are used, which allows a manipulation of conceptual task difficulty in terms of pair distance (difficult: one step, versus easy: three steps) on the series. Distances are varied for prime pairs and probe pairs orthogonally. NP effects were found for easy (wide) probe distances (Experiments 1 and 2) and, additionally, for easy (wide) prime distances (Experiment 2). This pattern is interpreted in terms of different theories of NP, which emphasize either forward-acting (prime to probe) or backward-acting (probe to prime) processes. The present results are most compatible with a backward-acting mechanism defined by the episodic retrieval perspective; they are less compatible with a forward-acting inhibition perspective. The results have implications for resource requirements of retrieval-based accounts of NP.

Sequential Modification and the Identification of Instructional Components Occasioning Self-Injurious Behavior

The present study describes a case of a 9-year-old girl diagnosed on the autism spectrum who averaged nearly 1200 hand-to-head self-injuries (+attempts) per school day. Given the resources of the school and the significance of the self-injurious behavior (SIB), analog functional analysis is not possible. Moreover, functional assessment results were inconclusive. Subsequent analyses suggested a relationship between SIB and instructional conditions, which we evaluated in an alternating treatments design that manipulated task difficulty, rate, interspersal, novelty, and order of presentation. This sequential modification of instructional components ultimately produced a methodology that is associated with an approximately 90% reduction in SIB. The study illustrates a strategy for treatment decision making in cases of serious problem behavior and when traditional functional behavioral assessment and functional analysis are inconclusive.

Psychological interpretation of the ex-Gaussian and shifted Wald parameters: A diffusion model analysis

A growing number of researchers use descriptive distributions such as the ex-Gaussian and the shifted Wald to summarize response time data for speeded two-choice tasks. Some of these researchers also assume that the parameters of these distributions uniquely correspond to specific cognitive processes. We studied the validity of this cognitive interpretation by relating the parameters of the ex-Gaussian and shifted Wald distributions to those of the Ratcliff diffusion model, a successful model whose parameters have well-established cognitive interpretations. In a simulation study, we fitted the ex-Gaussian and shifted Wald distributions to data generated from the diffusion model by systematically varying its parameters across a wide range of plausible values. In an empirical study, the two descriptive distributions were fitted to published data that featured manipulations of task difficulty, response caution, and a priori bias. The results clearly demonstrate that the ex-Gaussian and shifted Wald parameters do not correspond uniquely to parameters of the diffusion model. We conclude that researchers should resist the temptation to interpret changes in the ex-Gaussian and shifted Wald parameters in terms of cognitive processes. Supporting materials may be downloaded from http://pbr.psychonomic-journals.org/content/supplemental.