Interaction of Perception and Action in Discrete and Continuous Rapid Aiming Tasks

Previously, we have shown that discrete and continuous rapid aiming tasks are governed by distinct visuomotor control mechanisms by assessing the combined visual illusion effects on the perceived and effective index of difficulty (ID). All participants were perceptually biased by the combined visual illusion before they performed the rapid aiming tasks. In the current study, the authors manipulated the order of performing perceptual and motor tasks to examine whether perceptual or motor experience with the illusory visual target would influence the subsequent perceived and effective ID in discrete and continuous tapping tasks. The results supported our hypothesis showing that perceptual experience with the illusory visual target in the discrete condition reduced the effective ID in the subsequent discrete tapping task, and motor experience with the illusory visual target in the continuous condition reduced the illusion effects on the perceived ID in the subsequent perceptual judgment task. The study demonstrates the coinfluence of perception and action, and suggests that perception and action influence one another with different magnitude depending on the spatial frame of reference used to perform the perceptuomotor task.     

Perceptual and cognitive processes in time-to-contact estimation: Analysis of prediction-motion and relative judgment tasks

Three classes of task appear to involve time-to-contact (TTC) information: coincidence anticipation (CA) tasks, relative judgment (RJ) tasks, and interceptive actions (IAs). An important type of CA task used to study the perception of TTC is the prediction-motion (PM) task. The question of whether it is possible to study the perceptual processes involved in the timing of IAs using PM and RJ tasks is considered. A revised version of the tau hypothesis is proposed as an account of the perceptual information processing involved in the control of fast IAs. This draws on the distinction between “motor” and “cognitive” visual systems. It is argued that task variables affect whether “cognitive” information processing is involved in performance and can determine whether TTC information is used at all. Evidence is reviewed that suggests that PM and RJ tasks involve cognitive processing. It is argued that target viewing time, TTC at response initiation, amount of practice, and whether there is a period between target disappearance and response are task variables that determine whether cognitive processing will influence responding.     

Correlation of eye color on self-paced and reactive motor performance.

Researchers continue to examine the distinctiveness of motor performance by dark- versus light-eyed individuals. Dark-eyed individuals generally perform better at reactive type tasks (boxing, hitting a ball, defensive positions in football, rotary pursuit), while light-eyed individuals perform better at self-paced tasks (bowling, golf, pitching baseballs). Subjects performed two tasks, rotary pursuit and ball tossing (with light and dark background). Eye color (light or dark) and accuracy of performance were recorded for each subject. No significant difference was found between eye color and performance on the pursuit rotor (reactive activity). A significant difference was found between men's and women's performance in throwing a ball (self-paced activity) at a light-colored background.     

Processing two tasks with varying task order: central stage duration influences central processing order

In a recent study, Sigman and Dehaene (2006, PLoS Biology, 4, 1227–1238) reported that perceptual processing duration influences processing order of two tasks in the psychological refractory period paradigm (PRP). The present study examines whether the duration of central processes also influences processing order. For this purpose, we employed letter tasks with different central processing durations and varied task order in the PRP. In one part of the experiment, a tone discrimination task was combined with a similar time-consuming letter discrimination task. In the other part, the tone task was combined with a more time-consuming letter task, which required a mental rotation of the letter thereby prolonging central processing. If the duration of central processes influences processing order, participants should perform the tone task first more often when it is presented with the more time-consuming mental rotation task, than when it is presented with the similar time-consuming letter task. The results clearly confirm this prediction and thus show that not only perceptual processing duration but also central processing duration affects processing order in a dual-task situation. We suggest that the reported effect mirrors a tendency of participants to minimize total reaction time to both tasks by reducing slack time.     

Perceptual learning on inspection time and motion perception

Perceptual learning on simple perceptual tasks is interpreted as plasticity of neuronal populations in the sensory cortex (M. Fahle & T. Poggio, 2002). The authors examined individual differences on perceptual learning for 2 tasks-inspection time (IT) and a motion direction discrimination task that was instantiated as random dot kinematograms. The authors' main questions were whether individual differences in perceptual learning were consistent across the 2 tasks and whether perceptual learning correlated with cognitive abilities test scores. In all, 56 young adults completed 16 threshold estimations on 1 of 2 orthogonal versions of each task. Then, the authors made 2 further threshold estimations for the untrained, orthogonal version. Participants also completed a battery of 6 cognitive abilities tests that measured fluid ability (Gf) and perceptual speed (Gs). Perceptual learning was demonstrated for both tasks, but the degree of learning across tasks was not characteristic of the individual. Learning on IT correlated with Gs (r = .35), but learning on the motion direction discrimination task was unrelated to cognitive ability. Correlations of IT with cognitive measures were stable over the training period. IT was correlated with both the motion direction discrimination task (r = -.39) and an unmasked line length judgment task (r = -.31). The authors concluded that perceptual learning on IT correlates with cognitive abilities test scores, that correlations of IT with cognitive abilities test scores are stable as task performance improves with practice, and that the IT task is psychologically complex.     

Coincidence timing of finger, arm, and whole body movements

Two experiments investigated the effects of different types of movement responses on coincidence timing skill. The view was taken that the sensory-motor integration of the movement responses would be reflected in the accuracy and consistency of anticipation timing. A Bassin anticipation timer provided a light stimulus velocity of 3 mph for both experiments and the movements studied included a simple key press using a finger, an arm movement to a key press, and whole body movements culminating with a kick or step to a target. The experiments were modelled closely on the seminal study by Grose (1967). The results of Exp. 1 supported our prediction by demonstrating superiority of the finger task over the two larger movements for all measures of coincidence timing ability. The purpose of Exp. 2 was to compare the slightly different versions of the whole body task-that used in the first experiment and that used by Grose (1967). The results confirmed the close similarity of the two movement tasks and re-affirmed the results of Exp. 1. Exp. 2 also investigated sex effects on coincidence timing ability and, in contrast to previous evidence indicating that females perform with less accuracy and consistency than do males, no significant differences were found. Analysis of practice effects showed that, although there were no significant improvements over trial blocks in Exp. 1, there were significant improvements in Exp. 2. Comparisons with other research suggests that repeated practice in solving a coincident timing problem using whole body movements can lead to improved performance. In general, the findings are consistent with the constructs of action theory and emphasize the roles perceptual and movement variables have in defining situational constraints. Also, findings indicate that proficiency in coincidence anticipation appears to be influenced by the planning and organisation required for movement execution.     

Effect of speech task on intelligibility in dysarthria: a case study of Parkinson's disease

This study assessed intelligibility in a dysarthric patient with Parkinson's disease (PD) across five speech production tasks: spontaneous speech, repetition, reading, repeated singing, and spontaneous singing, using the same phrases for all but spontaneous singing. The results show that this speaker was significantly less intelligible when speaking spontaneously than in the other tasks. Acoustic analysis suggested that relative intensity and word duration were not independently linked to intelligibility, but dysfluencies (from perceptual analysis) and articulatory/resonance patterns (from acoustic records) were related to intelligibility in predictable ways. These data indicate that speech production task may be an important variable to consider during the evaluation of dysarthria. As speech production efficiency was found to vary with task in a patient with Parkinson's disease, these results can be related to recent models of basal ganglia function in motor performance.     

The coordination of compensatory tracking and anticipatory timing tasks

Two experiments investigated the presence of a coordination factor in a task consisting of compensatory tracking and anticipatory timing components. The task (Intercept task) resembles a computer game in which a rocket must be aimed and fired to shoot an incoming missile. The studies were designed to determine if a coordinating ability exists above and beyond the abilities needed to perform the component tasks alone. We also investigated the nature of coordination abilities through correlations with other types of coordination tasks and measures of intelligence. Is coordination a general cognitive ability that contributes to performance in a wide range of coordination tasks, or is coordination ability task specific? Multiple regression analyses indicated the existence of a coordination ability in the Intercept task. This coordination ability, however, was shown to be unrelated to the coordination of visual and linguistic processing and to psychometric measures of intelligence as assessed by the Armed Services Vocational Aptitude Battery (ASVAB). Coordination of visual and linguistic processing correlated with a component of the ASVAB measuring perceptual speed. We conclude that, although the ability to integrate separate components of a complex task draws on a coordination ability, this ability is domain specific and thus varies depending on the nature of the component tasks.     

Short-term retention during a simultaneous detection task

Subjects were required to perform a short-term memory task and a signal detection task, both individually and simultaneously. Memory performance was impaired only when the signals in the detection task were difficult to detect. The impairment in memory was restricted to items which appeared in the early positions of the list to be remembered. Detection performance was unaffected by the simultaneous task requirement and there was no correlation between performance on the two tasks when both were performed together. The results suggest that the difficulties Ss have when they attempt to perform several tasks at the same time may be due to limitations in the processes responsible for storing and retrieving information rather than those involved in the perceptual analysis of the incoming material.     

Perceptual asymmetries in normal children and children with attention deficit/hyperactivity disorder

Perceptual asymmetries in normal right-handed children (7-12 years of age) and children with attention deficit/hyperactivity disorder (ADHD), combined type, were investigated using various chimeric stimuli in free-viewing conditions. In the face-matching task, participants indicated which of two symmetrical face chimeras more closely resembled the original; in the chimeric faces task, participants indicated which of a pair of faces appeared happier; and in the grey scales task participants indicated which of two shaded rectangles appeared to be darker overall. Leftward biases were found for normal children with no effects of age. Contrary to expectations, normal leftward biases were also found for ADHD children in the face-matching and the chimeric faces tasks; however, a significant leftward bias was not observed in the grey scales task. The absence of anomalous perceptual bias in ADHD children on these purely perceptual tasks, suggests that anomalous perceptual asymmetries observed in other tasks (line bisection and cancellation tasks) may have been confounded by the motor response, and/or the explicit spatial components of those tasks.     

Individual differences in multiple types of shifting attention

Many researchers consider costs in shifting attention and mental set to reflect a basic ability to use top-down goal information to guide action. Although switch costs have been used as measures of individuals' executive function, whether common abilities underlie task set switching across different types of shifting tasks has not been well studied. In 249 participants, we studied whether switch costs in a novel two-choice reaction time task were correlated across variations in two variables: thelocus of representation (stimuli were either perceptually available or stored in working memory [WM]) and which of two judgment tasks was performed. Switch costs were asymmetrical, in that it was easier to switch to the easier judgment, and were related to overall and relative processing speed: Switch costs were higher when the task was more difficult. These factors should be accounted for when one is measuring individual differences in switch costs. After controlling for these effects, we found evidence for a common ability underlying switch costs that involved both task set preparation and response selection; however, residual shift costs, which involve only response selection, were uncorrelated across tasks. Correlations among switch costs were substantially higher within task type (e.g., correlations of WM shifting tasks with other WM shifting tasks and of perceptual tasks with perceptual ones), suggesting that there are also processes unique to switching within WM and switching among visible stimuli.     

Augmented Feedback Presented in a Virtual Environment Accelerates Learning of a Difficult Motor Task

One can use a number of techniques (e.g., from videotaping to computer enhancement of the environment) to augment the feedback that a subject usually receives during training on a motor task. Although some forms of augmented feedback have been shown to enhance performance on isolated isometric tasks during training, when the feedback has been removed subjects have sometimes not been able to perform as well in the "real-world" task as controls. Indeed, for realistic, nonisometric motor tasks, improved skill acquisition because of augmented feedback has not been demonstrated. In the present experiments, subjects (Experiment 1, N = 42; Experiment 2, N = 21) performed with a system that was designed for teaching a difficult multijoint movement in a table tennis environment. The system was a fairly realistic computer animation of the environment and included paddles for the teacher and subject, as well as a virtual ball. Each subject attempted to learn a difficult shot by matching the pattern of movements of the expert teacher. Augmented feedback focused the attention of the subject on a minimum set of movement details that were most relevant to the task; feedback was presented in a form that required the least perceptual processing. Effectiveness of training was determined by measuring their performance in the real task. Subjects who received the virtual environment training performed significantly better than subjects who received a comparable amount of real-task practice or coaching. Kinematic analysis indicated that practice with the expert's trajectory served as a basis for performance on the real-world task and that the movements executed after training were subject-specific modifications of the expert's trajectory. Practice with this trajectory alone was not sufficient for transfer to the real task, however: When a critical component of the virtual environment was removed, subjects showed no transfer to the real task.     

Visual, kinaesthetic and cross-modal development: relationships to motor skill development

The ability of children between the ages of 5 and 10 years to match the length of lines within and between the modalities of vision and kinaesthesis was studied. No evidence was found for specific increases in cross-modal skill which could not be explained in terms of within-modal development. Performance in the perceptual task was related to measures of developing motor skill in the children. Substantial relationships were found between performance on the within-modal tasks and motor skill, but no significant relationships were found between cross-modal measures and motor skill development. It is concluded that the development of cross-modal integration is not a major determinant of motor skill development.     

Stage analysis of the reaction process using brain-evoked potentials and reaction time

Summary Motor processes partly determine reaction time (RT) in both choice reaction time and in binary classification tasks. These latter tasks are popular in cognitive psychology because the experimenter believes that he has kept the motor component simple and constant and therefore can attribute changes in RT to perceptual or cognitive processes. In this paper we used the P3 component of the event-related potential (ERP) as a time marker indicating the duration of perceptual and cognitive processes. The latency of this component is believed to reflect stimulus evaluation time independent of response selection and organization time.Two types of tasks were used: a choice-reaction time task and a binary classification task. Signal similarity and S-R compatibility additively affected RT, but only signal similarity affected P3 latency. The number of items in the positive set and response type affected both P3 latency and RT. Relative response frequency changed the bias in the cognitive evaluation of the stimulus, reflected in the latency of the P3 component, and affected RT only if the subjects preset their motor system (indexed by the late CNV). A model was presented which proposes that motor processes may partially overlap with the perceptual and cognitive evaluation of the stimulus. Both ERPs and RT are necessary tools in the study of the relative timing of these processes.     

Age differences in dual-task interference are localized to response-generation processes

Dual-task differences in younger and older adults were explored by presenting 2 simple tasks, with the onset of the 2nd task relative to the 1st task carefully controlled. The possibility of an age-related reduction in the ability to generate and execute 2 similar motor programs was explored by requiring either a manual response to both tasks or a manual response to the 1st and an oral response to the 2nd and was confirmed by the evidence. The age-related interference was greater than would be expected from a general slowing of processing in older adults. The possibility of an age-related reduction in the capacity to process 2 tasks in the same perceptual input modality was explored by presenting both tasks in the visual modality or the 1st task in the auditory modality and the 2nd task in the visual modality and was not supported by the evidence. There was greater interference when both tasks were in the same modality, but it was equivalent for older and younger adults. Age differences in dual-task interference appear quite localized to response-generation processes.     

Perceptual grouping and distance estimates in typical and atypical development: comparing performance across perception, drawing and construction tasks

Perceptual grouping is a pre-attentive process which serves to group local elements into global wholes, based on shared properties. One effect of perceptual grouping is to distort the ability to estimate the distance between two elements. In this study, biases in distance estimates, caused by four types of perceptual grouping, were measured across three tasks, a perception, a drawing and a construction task in both typical development (TD: Experiment 1) and in individuals with Williams syndrome (WS: Experiment 2). In Experiment 1, perceptual grouping distorted distance estimates across all three tasks. Interestingly, the effect of grouping by luminance was in the opposite direction to the effects of the remaining grouping types. We relate this to differences in the ability to inhibit perceptual grouping effects on distance estimates. Additive distorting influences were also observed in the drawing and the construction task, which are explained in terms of the points of reference employed in each task. Experiment 2 demonstrated that the above distortion effects are also observed in WS. Given the known deficit in the ability to use perceptual grouping in WS, this suggests a dissociation between the pre-attentive influence of and the attentive deployment of perceptual grouping in WS. The typical distortion in relation to drawing and construction points towards the presence of some typical location coding strategies in WS. The performance of the WS group differed from the TD participants on two counts. First, the pattern of overall distance estimates (averaged across interior and exterior distances) across the four perceptual grouping types, differed between groups. Second, the distorting influence of perceptual grouping was strongest for grouping by shape similarity in WS, which contrasts to a strength in grouping by proximity observed in the TD participants.     

Inhibition of return in perception and action

Inhibition of return (IOR) refers to the delay in responses to previously cued locations. Whether IOR influences perceptual and/or motor processes has been controversial. To determine IOR effects on perception and action, this study examined IOR in spatially directed hand reaching (Experiment 1) and spatial localization of targets with a mouse cursor (i.e., an indirect visuomotor mapping/perceptual task; Experiment 2). The reaction times showed delayed responses for targets appearing within the whole cued hemifield for both tasks. However, hypometric spatial biases were consistently found only with directed reaching. Spatial biases in the mouse localization task were indirectly influenced by IOR and distinct from those in the reaching task. The dissociation in spatial characteristics for directed reaching vs. perception suggests that the effects of IOR are task dependent, but may be more directly linked to the dorsal motor system.     

Handedness and Reach-to-Place Kinematics in Adults: Left-Handers Are Not Reversed Right-Handers

The primary goal of this study was to examine the relations between limb control and handedness in adults. Participants were categorized as left or right handed for analyses using the Edinburgh Handedness Inventory. Three-dimensional recordings were made of each arm on two reach-to-place tasks: adults reached to a ball and placed it into the opening of a toy (fitting task), or reached to a Cheerio inside a cup, which they placed on a designated mark after each trial (cup task). We hypothesized that limb control and handedness were related, and we predicted that we would observe side differences favoring the dominant limb based on the dynamic dominance hypothesis of motor lateralization. Specifically, we predicted that the dominant limb would be straighter and smoother on both tasks compared with the nondominant limb (i.e., right arm in right-handers and left arm in left-handers). Our results only partially supported these predictions for right-handers, but not for left-handers. When differences between hands were observed, the right hand was favored regardless of handedness group. Our findings suggest that left-handers are not reversed right-handers when compared on interlimb kinematics for reach-to-place tasks, and reaffirm that task selection is critical when evaluating manual asymmetries.     

Deficits of motor intention following parietal lesions

Patients with lesions to the right parietal lobe were tested on their ability to reach to targets, or to respond verbally to targets. The targets occurred at the same two spatial locations--to the left and right of the patient--with the task being cued by the color of the target. Patients were able to perform both tasks separately rapidly and without error. However, when the two tasks were interleaved, they had difficulty making a response in the left (contralesional) field when this was different to a response that they had just made. These results suggest that lesions to the parietal cortex may cause a deficit in the coding for motor intention, as well as attention in the contralesional field.     

Independence of speed and accuracy in visual search: evidence for separate mechanisms.

Data from two studies that tested children's attention using visual search for a series of targets in a complex display and a sustained-attention task waiting for signals in a similar display were subjected to Factor Analysis to explore previous indications that speed and accuracy (the number of false alarms to nontargets) on this task reflect different mechanisms. The two factors identified confirmed the separation of these two measures and also suggested that the speed factor was related to Mental Age, while the accuracy factor was related to ratings of attentional ability. It is suggested that ratings of attentional ability reflect the efficiency of executive functions, displayed in the ability to inhibit responses to nontargets in these tasks, while speed of search is related to processing speed in the nervous system. Therefore intelligence and attentional ability depend on different underlying features of the nervous system.