Impulse variability in isometric tasks

An isometric elbow flexion task was used in two experiments that examined the influence of force-production characteristics on impulse variability. Impulse size was held constant while peak force, time to peak force, rate of force, and, hence, the shape of the criterion force-time curve were manipulated. The results indicated that changes in the force-time curve under conditions of equal impulse bring about systematic changes in impulse variability, and this effect is more pronounced for larger impulse conditions. The inability of existing functions to account for the peak force variability findings led to the generation of a new predicted force variability function. The proposed function accounts for changes in the standard deviation and coefficient of variation of peak force, impulse, and rate of force over a range of force-time conditions.     

Strategy execution in cognitive skill learning: an item-level test of candidate models

This article investigates the transition to memory-based performance that commonly occurs with practice on tasks that initially require use of a multistep algorithm. In an alphabet arithmetic task, item response times exhibited pronounced step-function decreases after moderate practice that were uniquely predicted by T. C. Rickard's (1997) component power laws model. The results challenge parallel strategy execution models as developed to date and they demonstrate that the shift to retrieval is an item-specific, as opposed to task-general, learning phenomenon. The results also call into question the entire class of smooth speed-up functions as global empirical learning laws. It is shown that overlaying of averaged item fits on averaged data can provide a sensitive test for model sufficiency. Strategy probes agreed with strategy inferences that were based on step-function speed-up patterns, supporting the validity of the probing technique.     

Demonstrating and eliminating the aggregation effect in physical skill tasks

Confidence judgments can be elicited in multiple ways. One of these procedures is to provide confidence judgments regarding each of a number of cases (individual judgments). A second procedure is to provide confidence judgments about a set of items (an aggregate judgment). Much research has demonstrated an aggregation effect—that individual judgments are more confident than aggregate judgments—within the cognitive knowledge domain. However, this effect has not previously been investigated with physical performance skill tasks. In three experiments, participants gave individual and aggregate judgments regarding the number of successful tosses they would make in either a ring toss, ping‐pong toss, or basketball toss task. In keeping with the aggregation effect, individual judgments were more confident than were aggregate judgments of success. Additionally, we eliminated the aggregation effect in Experiments 2 and 3 by employing a case‐specific base rate manipulation. Consistent with previous research with cognitive tasks, these results suggest that individual confidence judgments for physical skill tasks are determined primarily by characteristics associated with the individual case to be judged, whereas aggregate confidence judgments are determined by a more general evaluation of one's ability in the domain. Copyright © 2009 John Wiley & Sons, Ltd.     

Transfer of training and skill assumptions in tracking tasks

Matched groups of subjects were used to test the learning and transfer effects that follow changes in the display, the muscular reactions and the directional relationship between stimulus and response in a tracking task. Two arrangements were compared in the relationship studies: one arrangement of the stimuli and reactions was similar, and the other was opposed to that used in many every-day skills. The familiar arrangement was easier to learn. There was high positive transfer from the unfamiliar to the familiar, and little transfer from the familiar to the unfamiliar.

The physical dimensions of the display were varied to give two tasks with different stimuli. The initial learning times were equal for both tasks, and the transfer between them was high, positive, and equal. Two further tasks varied in the extent, speed and force of the required muscular movements. One task proved more difficult to learn initially, and there was greater transfer from the difficult to the easy task than from the easy to the difficult. A further experiment tested the effects of changing the difficulty of a tracking course, and it was found that learning was more rapid on the more difficult course. A difference in difficulty between two tasks, therefore, determined both the amount of transfer between them and the rate of learning the tasks.

New measures were developed to test the transfer between tasks of unequal content, and the effect of such inequalities upon the rate of learning. The findings are discussed, as are their possible implications for transfer measurement and their bearing upon existing theories of transfer.     

Signal clarity: an account of the variability in infant quantity discrimination tasks

Infants have shown variable success in quantity comparison tasks, with infants of a given age sometimes successfully discriminating numerical differences at a 2:3 ratio but requiring 1:2 and even 1:4 ratios of change at other times. The current explanations for these variable results include the two‐systems proposal – a theoretical framework that suggests that there are multiple systems at play and that these systems do not communicate early in infancy, leading to failure in certain numerical comparisons. An alternative proposal is that infants may be attending to continuous extent dimensions in these tasks rather than number per se. However, neither of these two main proposals is independently capable of accounting for the previously published data. Recently the Signal Clarity Hypothesis was proposed to account for and predict the variability (Cantrell & Smith, 2013). According to this hypothesis, infants’ variable success may be understood from a framework of statistical learning taken together with the signal‐to‐noise ratio generated by control procedures in habituation tasks. Here we test specific predictions made by the Signal Clarity Hypothesis. Across four experiments assessing 9‐month old discriminations of small and large sets (2 vs. 4 and 3 vs. 4), we demonstrate that infant success can be predicted by this novel approach and, further, that infants may discriminate smaller ratios of change than previously believed (3:4 numerical change and 2:3 cumulative area change).     

Soccer player's and closed-skill athletes' execution of a complex motor skill

The main purpose of this study was to investigate possible differences in speed and accuracy of motor execution among female soccer players in an Expert Soccer group, a Novice Soccer group, and a Closed-skill Athlete group. There were two main findings. Firstly, both soccer groups performed better than the Closed-skill Athletes on speed and accuracy of motor execution. Secondly, there were no significant differences between Expert and Novice soccer players in the speed and accuracy of motor execution.     

Attending to the execution of a complex sensorimotor skill: expertise differences, choking, and slumps

A simulated baseball batting task was used to compare the relative effects of attending to extraneous information (tone frequency) and attending to skill execution (direction of bat movement) on performance and swing kinematics and to evaluate how these effects differ as a function of expertise. The extraneous dual task degraded batting performance in novices but had no significant effect on experts. The skill-focused dual task increased batting errors and movement variability for experts but had no significant effect on novices. For expert batters, accuracy in the skill-focused dual task was inversely related to the current level of performance. Expert batters were significantly more accurate in the skill-focused dual task when placed under pressure. These findings indicate that the attentional focus varies substantially across and within performers with different levels of expertise.     

Differential components of the manual and vocal Stroop tasks

In this study, four components of the Stroop effect were examined for manual word and vocal responses. The components were lexical, semantic relatedness, semantic relevance, and response set membership. The results showed that all four components were present in the vocal response task. However, in the manual word response task, the only component that produced significant interference on its own was response set membership. These results do not support predictions made by recent translation models (see W. R. Glaser & M. O. Glaser [1989] and Sugg & McDonald [1994]). A possible solution was suggested that located two sites for Stroop interference. The lexical, semantic relatedness, and semantic relevance effects were located in the lexical system, whereas the response set membership effect was located at a response selection stage.     

The effect of personality variables in the prediction of the execution of different prospective memory tasks in the laboratory

The study of prospective memory (ProM), the remembering of the delayed execution of intentions, has been growing in recent years, and we know quite a bit about the cognitive variables that affect it. But the performance of a task depends on personality variables as well as on cognitive ones, and the role of personality variables in ProM has only been partially studied, the results being less conclusive. We sought to address two main objectives: (1) to quantify the joint influence of cognitive and personality variables on three ProM tasks in the laboratory (two based on events and the other on time), and (2) to identify the personality profiles of those who perform well in these three ProM tasks as opposed to those who do not. The cognitive and personality variables were evaluated with two sessions of 157 participants. The 16 PF-5 was applied (Cattell, Cattell & Cattell, 1993) and other cognitive variables were measured. With the data obtained, we ran several regression analyses to determine how some cognitive variables (sustained attention, verbal fluency, interference, retrospective memory, selective attention) and personality factors (tested using the 16 PF-5) can help to explain the variance in the performance of prospective memory tasks. Our results show that the contribution of personality predictor variables is moderate and smaller than that of the cognitive variables for predicting the execution of ProM tasks in the laboratory. Furthermore the intervention of the personality variables differs depending on the ProM tasks used. Global self-control and rule-consciousness were the personality variables that contributed the most in the prediction of the scores in the ProM tasks that were used.     

Movement variability and skill level of various throwing techniques

In team-handball, skilled athletes are able to adapt to different game situations that may lead to differences in movement variability. Whether movement variability affects the performance of a team-handball throw and is affected by different skill levels or throwing techniques has not yet been demonstrated. Consequently, the aims of the study were to determine differences in performance and movement variability for several throwing techniques in different phases of the throwing movement, and of different skill levels. Twenty-four team-handball players of different skill levels (n=8) performed 30 throws using various throwing techniques. Upper body kinematics was measured via an 8 camera Vicon motion capture system and movement variability was calculated. Results indicated an increase in movement variability in the distal joint movements during the acceleration phase. In addition, there was a decrease in movement variability in highly skilled and skilled players in the standing throw with run-up, which indicated an increase in the ball release speed, which was highest when using this throwing technique. We assert that team-handball players had the ability to compensate an increase in movement variability in the acceleration phase to throw accurately, and skilled players were able to control the movement, although movement variability decreased in the standing throw with run-up.     

Decomposition of repetition priming components in picture naming

Cognitive mechanisms underlying repetition priming in picture naming were decomposed in several experiments. Sets of encoding manipulations meant to selectively prime or reduce priming in object identification or word production components of picture naming were combined factorially to dissociate processes underlying priming in picture naming. Experiments 1, 2, and 3 were conducted with Spanish-English bilingual participants and bilingual materials. Experiments 4, 5A, and 5B were single-language experiments in English or Spanish. A simple process model was used to formalize the theoretical predictions and test them across all experiments simultaneously. Object identification and word production processes were selectively influenced in an additive manner, which suggests that the 2 sets of processes are independent and sequential. The patterns of facilitation support a quantitative model of transfer-appropriate processing in which shared processes from encoding to test are the causal basis and speeded processes are the mechanism of facilitation.     

Modeling parallelization and flexibility improvements in skill acquisition: from dual tasks to complex dynamic skills

Emerging parallel processing and increased flexibility during the acquisition of cognitive skills form a combination that is hard to reconcile with rule-based models that often produce brittle behavior. Rule-based models can exhibit these properties by adhering to 2 principles: that the model gradually learns task-specific rules from instructions and experience, and that bottom-up processing is used whenever possible. In a model of learning perfect time-sharing in dual tasks (Schumacher et al., 2001), speedup learning and bottom-up activation of instructions can explain parallel behavior. In a model of a complex dynamic task (Carnegie Mellon University Aegis Simulation Program [CMU-ASP], Anderson et al., 2004), parallel behavior is explained by the transition from serially organized instructions to rules that are activated by both top-down (goal-driven) and bottom-up (perceptually driven) factors. Parallelism lets the model opportunistically reorder instructions, leading to the gradual emergence of new task strategies.     

Cognitive demands of error processing associated with preparation and execution of a motor skill

Maxwell et al. [Maxwell, J. P., Masters, R. S. W., Kerr, E., & Weedon, E. (2001). The implicit benefit of learning without errors. The Quarterly Journal of Experimental Psychology, 54A, 1049–1068. The implicit benefit of learning without errors. The Quarterly Journal of Experimental Psychology, 54A, 1049–1068] suggested that, following unsuccessful movements, the learner forms hypotheses about the probable causes of the error and the required movement adjustments necessary for its elimination. Hypothesis testing is an explicit process that places demands on cognitive resources. Demands on cognitive resources can be identified by measuring probe reaction times (PRT) and movement times. Lengthened PRT and movement times reflects increased cognitive demands. Thus, PRT and movement times should be longer following errors, relative to successful, movements. This hypothesis was tested using a motor skill (golf putting). Furthermore, the association between error processing and the preparation and execution phases of movement was examined. The data confirmed that cognitive demand is greater for trials following an error, relative to trials without an error. This effect was apparent throughout learning and in both the preparatory and execution phases of the movement. Cognitive effort also appeared to be higher during movement preparation, relative to movement execution.     

Cognitive biases in three prediction tasks: A test of the cognitive model of depression

Cognitive therapy for depression is based on an assumption that depressed individuals have inaccurate, negative biases. Whether this assumption is accurate remains unresolved. Thus, this study sought to examine the relationship between depressive symptoms and bias in three sets of predictions (i.e., predictions of future life events, how one would be rated by a significant other, and performance on a vocabulary test). Following study announcements made to a subset of people pre-screened for depressive symptoms, 85 participants with widely varying depressive symptoms (17 of whom met diagnostic criteria for depression) made predictions on three judgment tasks and the outcomes for these tasks were assessed. Optimistic/pessimistic biases were related to depressive symptoms for each of the three tasks. Participants with high levels of depressive symptoms and depressed participants exhibited substantial pessimistic bias. Those high in depressive symptoms exhibited significant pessimistic bias on all three tasks. Participants meeting diagnostic criteria for depression exhibited pessimistic bias on two of three tasks. There was no evidence that depressive symptoms were associated with greater accuracy in judgments. Results are largely consistent with cognitive models of depression which postulate that depression is associated with pessimistic biases.     

An event-related visual occlusion method for examining anticipatory skill in natural interceptive tasks

This article describes a new automated method for the controlled occlusion of vision during natural tasks. The method permits the time course of the presence or absence of visual information to be linked to identifiable events within the task of interest. An example application is presented in which the method is used to examine the ability of cricket batsmen to pick up useful information from the prerelease movement patterns of the opposing bowler. Two key events, separated by a consistent within-action time lag, were identified in the cricket bowling action sequence—namely, the penultimate foot strike prior to ball release (Event 1), and the subsequent moment of ball release (Event 2). Force-plate registration of Event 1 was then used as a trigger to facilitate automated occlusion of vision using liquid crystal occlusion goggles at time points relative to Event 2. Validation demonstrated that, compared with existing approaches that are based on manual triggering, this method of occlusion permitted considerable gains in temporal precision and a reduction in the number of unusable trials. A more efficient and accurate protocol to examine anticipation is produced, while preserving the important natural coupling between perception and action.     

Evaluation of three sensitivity measures in magnitude estimation tasks

Taking into account the studies about the measure of sensitivity in magnitude estimation tasks, we analyze the three most common measures used in this topic: Pearson's product-moment correlation between the logarithm of the stimulus and the logarithm of the response (R), the exponent of Stevens' power function (K), and the measure "M" proposed by Garriga-Trillo. Using a sample of participants greater than usual in psychophysical studies (180 participants), we designed an experiment with two sets of stimuli with different stimulus ranges. In each of these sets, we used two kinds of stimuli (line segments and squares). Our conclusions were: (1) we rejected the use of K as a sensitivity measure because the results provided by this index were the opposite of those expected when we compared the two stimulus ranges. (2) We also rejected the use of M because this measure is a linear transformation of Kendall's coefficient of concordance. (3) Lastly, we suggest the mathematical transformation proposed by Fisher to achieve a normal distribution, and recommend this transformation as the best sensitivity measure.     

Posture and motion variability in non-repetitive manual materials handling tasks

In developing a motion prediction model it is important to initially consider the sources of variability that a model should reproduce. This initial step is followed by model evaluation, where the variability predicted by the model can be a useful test parameter. An existing lifting-motion dataset collected under controlled laboratory conditions was employed here to evaluate quantitatively some important sources of variability for lift motion modeling. The main source of variability was the segment being analyzed, which accounted for more than 20% of the overall variability. There was substantial left-right symmetry in individual segment variability estimates, which were largest for the upper arm segment and tended to be larger for the upper limbs than the lower limbs. Task-related factors accounted for variability mainly as a function of the segment being considered. Within-participant variability contributions to the dataset were relatively small, whereas the contribution of between-participants variability was dependent on the segment (as large as 50%) and could indicate different lifting strategies across participants. Variability was found to remain relatively constant across the different stages of the lifting movements. Implications of these results for the development and evaluation of motion prediction models are presented. Specifically, while task characteristics may be important modifiers of the mean segment trajectory during a lifting movement, their influence on variability differs based on the segment that is being considered. The relevance of the findings is discussed in terms of their utility in the ergonomic design of tasks and work spaces.