Motivational control of motor performance by goal setting in a dual-task situation

Summary The goal-setting approach to task motivation is applied to examine the way in which subjects control their performance on two concurrently performed tasks under the guidance of different goals in a dual-task situation. The tasks were a simple auditory-manual reaction time (RT) task and a visual-manual pursuit-tracking task. The goal conditions assigned alternatively to the tasks differed with respect to goal specificity and feedback information (KR) given after the trials. It is shown that the improvement of performance in the task with hard, specific goals is achieved in both cases at the cost of the concurrently performed other task which, on the basis of a lack of feedback and a rather unspecific goal instruction, should have a lower priority. The data reveal some strategies hidden behind these overall changes of the average performance at both tasks. For the RT task, the adjustment to the different goals is mainly achieved by changes in the temporal control or preparatory processes as can be inferred from the RT distributions as well as from the analysis of some typical errors. For the tracking task, changes in the tracking accuracy within the overlapping RT intervals are the best indicators for the performance control under the different goal conditions.This research was supported by a grant from the Deutsche Forschungsgemeinschaft (Kl 408/4-2)     

Two distinct pathways for developmental coordination disorder: persistence and resolution

This article describes the perceptual motor, educational and social outcome of early motor delay in a group of 17-18 year old Finnish adolescents who were originally evaluated at age 5. The study group consisted of 65 adolescents: 22 with significant motor problems (or developmental coordination disorder, DCD), 23 with minor motor problems (intermediate group) and 20 controls. The goal of this study was to reassess the results obtained when they were age 15 and to determine whether the variables used earlier could still discriminate the adolescents at age 17. The results showed that at age 17 all perceptual motor tasks differentiated the three groups. The DCD group performed less well than the control group on all tasks, with the intermediate group situated between these two. Discriminant function analyses showed that more classification errors occurred between the control and intermediate groups at age 17 than at age 15, suggesting that the distinction between these groups becomes more difficult with age. In the educational domain, similar to the findings at age 15, the adolescents with DCD had the lowest WAIS scores and shortest school careers of the three groups. In the social domain, as found two years earlier, the DCD group had the lowest perceptions of athletic and scholastic competence while the intermediate and control groups did not differ. In addition, the interview results indicated that the three groups were in different stages of identity development. In sum, the outcome at age 17 was a replication of the results obtained at age 15 and suggests two developmental paths for those with early perceptual motor problems: 'persistence' and 'catching up'.     

Selective disruption of hypermnesia for pictures and words

In this study, we investigated the effects of various interpolated tasks on hypermnesia (improved recall across repeated tests) for pictures and words. In five experiments, subjects studied either pictures or words and then completed two free-recall tests, with varying activities interpolated between the tests. The tasks performed between tests were varied to test several hypotheses concerning the possible factor(s) responsible for disruption of the hypermnesic effect. In each experiment, hypermnesia was obtained in a control condition in which there was no interpolated task between tests. The remaining conditions showed that the effect of the interpolated tasks was related to the overlap of the cognitive processes involved in encoding the target items and performing the interpolated tasks. When pictures were used as the target items, no hypermnesia was obtained when subjects engaged in imaginal processing interpolated tasks, even when these tasks involved materials that were very distinct from the target items. When words were used as the target items, no hypermnesia was obtained when the interpolated tasks required verbal/linguistic processing, even when the items used in these tasks were auditorily presented. The results are discussed in terms of a strength-based model of associative memory.     

An automated system for administering continuous workload and for measuring sustained continuous performance

Sustained continuous performance for up to 42 h was studied with 60 male volunteers in two separate protocols. The recuperative value of six 1-h nap breaks and a single 6-h nap break were contrasted in 20 subjects, 10 in each nap group. Forty other subjects attempted to work continuously with no breaks for 42 h. Twenty of these subjects worked simultaneously on separate parallel computer-based tasks, but worked in the same room in pairs. All subjects in the two nap groups (N=10 and N=10), as well as 20 who had no scheduled breaks, worked alone, almost isolated, with minimal interaction with the experimenters. During each 10 min, subjects performed a tracking task, a pattern-memory task, and an addition task and provided subjective ratings on sleepiness and attention/fantasy. Results showed that computerized tasks demanding sustained continuous performance without naps cause more rapid performance deterioration than previously tested intermittent-work paradigms.     

Involuntary strategy-dependent dual task performance

Previous studies showed that some dual tasks can be performed simultaneously without costs. Yet, a variable SOA between the inputs to such tasks leads to strategic, often involuntary, prioritization of one of the two tasks. Here we explore the boundary conditions for this involuntary or exogenous strategy. In Experiment 1, subjects were initially trained on dual task performance where the input to the two tasks is presented simultaneously (0 SOA). We used two tasks that under such conditions can be performed without costs and indeed subjects displayed perfect sharing of the tasks. Subjects then performed the same two tasks but with a variable SOA (0, 50, 150, 800?ms). This manipulation led to a serial-like performance of the two tasks even in trials with 0 SOA. In Experiment 2, subjects participated in eight sessions. Within each session, they performed in alternation blocks with a fixed 0 SOA and blocks with a variable SOA. Subjects displayed perfect sharing in the pure 0 SOA blocks but performed the two tasks serially in the mixed SOA blocks despite receiving identical instructions. These findings demonstrate that task context is a powerful factor in dual task performance and may lead subjects to involuntarily exhibit dual task costs even in conditions where they can perform the tasks without any costs. Moreover, these findings strongly suggest that costs observed in PRP studies reflect the use of such exogenous strategies rather than a general structural dual task limitation.     

Mediating factors in the arousal-performance relationship

The arousal-performance relationship was investigated within a social facilitation experiment, in which two major task dimensions (cognitive-motor and difficulty) were manipulated and two arousal measures (palmar sweat and self-reports) were taken. Subjects (75 male and 75 female introductory psychology students) were randomly assigned to one of five audience conditions and one of three task difficulty levels. Each subject performed three tasks, which varied as to cognitive and motor requirements, under a uniform difficulty level. No significant differences were found on any arousal or performance measure due to the audience manipulation. Females were found to be more aroused by the audiences than males, on both arousal measures. When self-reported arousal scores were quintiled to create five post hoc arousal conditions, significant interactions between these conditions and task difficulty level were obtained for both the cognitive and motor tasks. (No significant differences were found using quintiled palmar sweat scores.) On the basis of the similar pattern of these interactions, it was concluded that the inverted-U function was obtained only on high-difficulty tasks.     

Symbolic comparisons with and without perceptual referents: Is interval information used?

In an attempt to investigate the range effect obtained by Moyer and Bayer (1976), two groups of subjects were taught to associate colors with circles that differed in size by larger or smaller intervals and then participated in a symbolic comparison task, in which they determined which of two simultaneously presented symbols (the first letters of two colors) represented the larger magnitude. A third group of subjects, who merely learned an arbitrary ordering of the colors along the dimension of size, also participated in the symbolic comparison task. Despite the fact that no practice trials were given, there was no effect of interval size in either early or late blocks, and the circle-learning groups did not differ in performance from the group who only learned an arbitrary ordering of colors, even when pairs containing end terms were removed from the analysis. It is concluded that subjects do not use analogue codes in symbolic comparison tasks involving small, repeated sets of arbitrarily defined symbols.     

Dementia and working memory

This study explored the hypothesis that patients suffering from dementia of the Alzheimer type (DAT) are particularly impaired in the functioning of the Central Executive component of working memory, and that this will be reflected in the capacity of patients to perform simultaneously two concurrent tasks. DAT patients, age-matched controls and young controls were required to combine performance on a tracking task with each of three concurrent tasks, articulatory suppression, simple reaction time to a tone and auditory digit span. The difficulty of the tracking task and length of digit sequence were both adjusted so as to equate performance across the three groups when the tasks were performed alone. When digit span or concurrent RT were combined with tracking, the deterioration in performance shown by the DAT patients was particularly marked.     

Cognition and mood in relation to the performance of squash tasks

The purpose of this investigation was to determine the role of cognition and mood in the performance of squash tasks, with particular reference to attention and self-reported arousal and stress. Volunteer male subjects (n = 40), divided into three ability groups, 'skilled', 'average' and 'novice', were required to perform two squash tasks with different degrees of difficulty. Order of presentation of the tasks was controlled. Results indicated that subjects completing the easier squash task first performed better on the subsequent difficult task than those subjects who completed the more difficult task first. No differences in scores across tasks were found for subjects completing the tasks in reverse order. Performance was related to level of skill. Furthermore, significant differences in attentional style were revealed when average subjects were compared with skilled and novice players. Skilled players were also found to exhibit significantly different personality characteristics from novice players. Specifically, skilled players exhibited higher levels of extraversion and appeared less neurotic. For the average and novice groups, reports of high levels of stress accompanied those of high levels of arousal and these remained constant throughout the experiment. By contrast, for the skilled group low levels of stress accompanied high levels of arousal. The results are discussed in terms of the effects of these cognitive and mood factors on performance and a suggested direction for future research is offered.     

Age trends in children's time-sharing performance

To investigate developmental differences in time-sharing performance, 60 boys, 20 in each of three age groups (7-, 10-, and 13-year-olds) performed an auditory matching task and a tracking task alone and concurrently, the latter under two sets of instructions. Decrements produced by concurrent performance were compared for the three age groups. When the time-shared tasks were presented as equally important, time-sharing produced significantly greater proportional decrements in the tracking performance of the younger children and for all age groups tracking task decrements were directly related to matching task difficulty. Subsequently, the children were instructed that one or the other of the tasks was more important and that they were to improve their performance on that task. All three age groups showed a significant improvement on the task emphasized by instructions. The relationship of the results to two models of information processing is discussed.     

On Separability of and Interference Between Tracking Dimensions in Dual-Axis Tracking

Time-shared tasks may conceivably be separable or integral. A case in which the question of separability seems quite relevant is dual-axis tracking. To test the interaction between tracking dimensions, we first studied whether they interfere with each other. Practiced subjects performed tracking on one or two axes, with or without feedback indicators and with or without a requirement to allocate resources unevenly between axes. They also performed with or without a concurrent binary classification of visually presented digits which were presented within a moving square that served as the target for tracking. Small deficits were found in the performance of both tracking and digit classification when performed together. However, the conditions of tracking did not have a discernible effect on either tracking or digit classification. Hence, the introduction of a second tracking axis probably does not have harmful consequences either on tracking itself or on any other task time-shared with tracking.

Further studies were conducted to examine whether the absence of an effect of number of tracking axes is due to their integrality. Ordinary position tracking was paired either with another similar task on the other axis or with a novel sort of tracking in which subjects had to continually match sizes of moving rectangles. Tasks were paired under both divided-attention and focused-attention instructions. No interference on position tracking was observed even when the types of task on the two axes differed, and no other evidence for integrality of the homogeneous task pairs was found.     

On separability of and interference between tracking dimensions in dual-axis tracking

Time-shared tasks may conceivably be separable or integral. A case in which the question of separability seems quite relevant is dual-axis tracking. To test the interaction between tracking dimensions, we first studied whether they interfere with each other. Practiced subjects performed tracking on one or two axes, with or without feedback indicators and with or without a requirement to allocate resources unevenly between axes. They also performed with or without a concurrent binary classification of visually presented digits which were presented within a moving square that served as the target for tracking. Small deficits were found in the performance of both tracking and digit classification when performed together. However, the conditions of tracking did not have a discernible effect on either tracking or digit classification. Hence, the introduction of a second tracking axis probably does not have harmful consequences either on tracking itself or on any other task time-shared with tracking. Further studies were conducted to examine whether the absence of an effect of number of tracking axes is dues to their integrality. Ordinary position tracking was paired either with another similar task on the other axis or with a novel sort of tracking in which subjects had to continually match sizes of moving rectangles. Tasks were paired under both divided-attention and focused-attention instructions. No interference on position tracking was observed even when the types of task on the two axes differed, and no other evidence for integrality of the homogeneous task pairs was found.     

Resources, confusions, and compatibility in dual-axis tracking: displays, controls, and dynamics

Why do people often find that performing two tasks at once is harder than performing one task at a time? Three mechanisms of task interference that might answer that question were investigated: resource competition, confusions, and incompatible task proximity between processing stages. The subjects performed dual-axis compensatory tracking with error displays that were either integrated or separated, with axis controls that either were integrated into one stick or remained separate, and with control dynamics on the two axes that were either the same or different. Tracking error increased and control activity decreased as a function of the combined difficulty of the two control dynamics. Integrated displays and integrated controls both led to increased confusions between tracking axes although error was not reliably affected. Significantly, performance was also affected by whether the integrality of displays matched that of controls. These results suggest that resource competition, confusions, and compatibility of proximity play distinct roles in dual-axis tracking performance.     

Effects of two tasks and two levels of difficulty upon surface electrogastrograms

The effects of differentiation, novelty, and difficulty of ability tasks upon electrogastrographic activity of healthy subjects during digestion were investigated. Electrical recording of activity of the stomach by means of surface electrodes was performed in 40 healthy volunteers before and after easy or hard tasks. 20 subjects had to complete puzzles; the others had mental arithmetic. Both groups were matched in terms of scores on easy and difficult tasks. Baseline recordings were performed before each trial. The number of waves with peak amplitude greater than 100 mu v on electrogastrographic recording during each time span was measured, using a visual analysis. There was a significant decrease in number of waves/min, during task performance. A more pronounced decrease was produced by subjects working on puzzles than those working on mental calculation and by subjects working on easy tasks than those working on difficult tasks when the easy preceded the difficult ones. A larger decrease was obtained when the tasks of comparable difficulty were performed first. Emotional correlates such as anger and irritability were suggested to play a role in the interpretation of results.     

Insight without awareness: On the interaction of verbalization, instruction and practice in a simulated process control task

Four experiments in which subjects learned to control two versions of a complex simulated process control task show that verbalizable knowledge of procedures used to perform these tasks is very limited and is acquired late in learning. Individual learning curves associated with these tasks showed sudden improvements in performance, which were not accompanied by a similar increase in verbalizable knowledge. It was also found that verbal instructions consisting of exemplar memorization, strategies for rule induction, simple heuristics, and experts' instructions were all effective in enhancing novice subjects' performance. A theoretical framework is proposed in which subjects draw on two separate but interacting knowledge structures to perform these tasks. One knowledge structure is based on memory for past experiences (close analogies), and the other is based on one's current mental model of the task. Implicit sets of competing rules that control response selection are derived from both sources of knowledge. It is suggested that dissociations between task performance and verbalizing occur because memory-based processing tends to have more control over response selection because of its greater specificity, whereas a mental model tends to be the preferred mode for verbal reporting because of its greater accessibility.     

EEG alpha asymmetry: task difficulty and hypnotizability

Parieto-occipital EEG alpha was recorded bilaterally, while 20 high- and 20 low-hypnotizable women performed one left-hemisphere and one right-hemisphere task of low difficulty and two other comparable tasks of high difficulty. Every task was performed twice, once with eyes open and once with eyes closed. All subjects were right-handed. The tasks were originally selected to be of high and low difficulty. The subjective rating of task-difficulty was also evaluated. The integrated amplitude alpha and the alpha ratio (R-L/R + L) were the dependent variables. The highly hypnotizable women showed significantly higher alpha amplitude in eyes-closed condition than the low scorers; this difference disappeared during task performance and in the eyes-open condition. The left-tasks showed lower alpha amplitude in both hemispheres than right-tasks and baseline. The right-hemisphere alpha amplitude was lower than left in all experimental conditions. On tasks of high and low difficulty there was different hemispheric behavior on right and left tasks. Performance reflecting the right and left hemispheres in the low-difficulty condition showed no changes between baseline, right- and left-tasks, while under high difficulty there was a decrease in alpha amplitude in the right and even more marked decrease in the left hemisphere during left-tasks. The pattern of task effects for ratio scores was the same as for alpha amplitude, however, despite the analysis of alpha scores, an interaction of hypnotizability X task-difficulty was detected. The highly hypnotizable women showed less negative alpha ratio during a task of low difficulty than during tasks of high difficulty; the reverse was true for the low-hypnotizable women. Finally, the highly hypnotizable subjects showed less subjective difficulty during performance than the low scorers.     

The Assessment of Limb Apraxia: An Investigation of Task Effects and Their Cause

To test the effects of variations in the structure of tasks used to assess limb apraxia, eight tasks—differing in their modes of elicitation (tactile, verbal, visual, imitation) and/or types of movement elicited (transitive, intransitive, meaningless)—were administered to 25 carefully selected subjects with idiomotor limb apraxia. When standardized scores (based on the performance of 10 nonneurologically impaired control subjects) were used to measure the differences between tasks, no clinically significant task effects were found. Additional investigation was made of two causal hypotheses regarding the processes underlying limb apractic performance. The results of factor analyses and a search for double dissociations among individual subjects were consistent with the (severity) hypothesis that differences in task performances (raw scores) reflect degrees of task difficulty; and they failed to support the (disconnection) hypothesis that posits separate and independent neural/mental processes underlying task performances.     

Temperament,classmate likability,and social perspective coordination as correlates of children's parent-rated type A behaviors

Parents of 58 boys and 62 girls from grades three through eight completed the Matthews Youth Test for Health (MYTH), a measure of Type A behavior. Normative and reliability data were similar to those obtained from teachers as reported in the literature, but a factor analysis of parents' ratings revealed four factors (Competitiveness, Irritability, Impatience, and Leadership) as opposed to the two factors (Impatience/Aggression and Competitiveness) that have been derived from teacher ratings. Boys had higher total MYTH scores than girls, but correlations with age were not significant. No grade or gender effects were obtained for any of the four MYTH factor scores. Correlates of the MYTH scores were computed separately for boys and for girls. For boys, Irritability was related to Reactivity, a Difficult Temperament, low classmate Likeability, and poor performance on two social cognitive tasks (compromising and friendship understanding). For girls, Leadership was related to Classmate Likeability and good performance on the two social cognitive tasks. For boys only, total MYTH scores were related to low Attention Span, high Reactivity, a Difficult Temperament, and low Friendship Understanding scores. Findings are related to the gender differences found in the study of both ego control and cooperation/ competition.     

The effects of divided attention on information processing in manual tracking.

Six subjects performed a manual tracking task concurrently uith each of two secondary tasks: in input task (auditory signal detection) and an output task (application of a constant force). A feedback-control analysis of tracking performance was utilized to analyze the time-sharing decrements observed in mean squared errer, in terms of components due to processing delay, addition of internal processing noise, and change in response bias (tracking gain). The results indicated that only the parameters measuring noise and gain were sensitive to time-sharing conditions, and these only to concurrent performance of the force application task. It is concluded that limits of attention in dual-task performance are more severe in output than in input stages of processing, but that these limits are not necessarily those of a single-channel bottleneck. Instead, a broader conception of attention is proposed: one that included changes in processing noise and shifts in response bias, as attention-related phenomena.     

Individual and sex differences in reminiscence

Inverted alphabet printing, rotary pursuit, and mirror tracking tasks were administered to 84 subjects in order to ascertain (a) reproducibility of reminiscence scores within and between tasks and (b)sex differences in reminiscence. With prerest performance levels held constant by second-order partial correlation procedures, reproducibility of individual reminiscence differences within tasks was significant but quite low, while predictability of reminiscence from one task to another was negligible. The sexes reminisced essentially alike on inverted alphabet printing, but females reminisced more than males on the other tasks, presumably because they were relatively more depressed by massed practice on these tasks. Thus, individual and sex differences were essentially task specific. Implications of results for reminiscence theories and for the credibility of alleged relationships between reminiscence and other organismic variables were discussed.