Partial visual feedback and spatial end-point accuracy of discrete aiming movements

Five experiments are reported in which the effect of partial visual feedback on the accuracy of discrete target aiming was investigated. Visual feedback was manipulated through a spectacle-mounted liquid-crystal tachistoscope. The length of the visual feedback interval was varied as a percentage of the instructed movement time. In Experiment 1, the length of the vision interval was manipulated symmetrically at the beginning- and end-phase of the movement, whereas in the remaining experiments, the vision time was varied with respect to the end-phase only. The variations at the end were examined for different distances (Experiment 2), different movement speeds at the same distance (Experiment 3), and in small interstep intervals (Experiment 4). A vision time of more than 150 ms at the end-phase of the movement enhanced aiming performance in all experiments. Longer vision times monotonously improved aiming accuracy; the fifth experiment showed that a vision time of about 275 ms was sufficient for near-perfect aiming. Furthermore, the significance of vision during the first phase of a movement was demonstrated again. The results of the five experiments pointed to shorter visuomotor processing times. To explain the beneficial effects of short vision times for aiming accuracy, we propose a model of visuomotor processing that is based on the stochastic optimized submovement model of Meyer, Abrams, Kornblum, Wright, and Smith (1988).     

Rapid visual feedback processing in single-aiming movements

A major line of behavioral support for motor-program theory derives from evidence indicating that feedback does not influence the execution and control of limited duration movements. Since feedback cannot be utilized, the motor-program is assumed to act as the controlling agent. in a classic study, Keele and Posner observed that visual feedback had no effect on the accuracy of 190-msec single-aiming movements. Therefore visual feedback processing time is greater than 190 msec, and, more importantly, limited duration movements are governed by motor programs. In the present paper, we observed that visual feedback can affect the spatial accuracy of movement with durations much less than 190 msec. We hypothesize that visual feedback can aid motor control via processes not associated with intermittent error corrections.     

The utilization of visual feedback information during rapid pointing movements

Three experiments were conducted to determine how variables other than movement time influence the speed of visual feedback utilization in a target-pointing task. In Experiment 1, subjects moved a stylus to a target 20 cm away with movement times of approximately 225 msec. Visual feedback was manipulated by leaving the room lights on over the whole course of the movement or extinguishing the lights upon movement initiation, while prior knowledge about feedback availability was manipulated by blocking or randomizing feedback. Subjects exhibited less radial error in the lights-on/blocked condition than in the other three conditions. In Experiment 2, when subjects were forced to use vision by a laterally displacing prism, it was found that they benefited from the presence of visual feedback regardless of feedback uncertainty even when moving very rapidly (e.g. less than 190 msec). In Experiment 3, subjects pointed with and without a prism over a wide variety of movement times. Subjects benefited from vision much earlier in the prism condition. Subjects seem able to use vision rapidly to modify aiming movements but may do so only when the visual information is predictably available and/or yields an error large enough to detect early enough to correct.     

Attentional strategies and the visual control of discrete movements

The relationship between the availability of visual information and attention demands during the production of a discrete motor act was examined. Subjects were required to move a linear slide a distance of 15 cm in both 150 and 600 msec conditions under three light manipulations, viz., light always on; light always terminated as movement began; or, subject was unsure as to whether light would stay on or terminate. A simple key press by the index finger of the opposite hand to a tone was used as a secondary task and a measure of attention demands. The light manipulation influenced attention demands on the rapid 150 msec movement such that more attention was demanded when the subject knew the light would terminate. No such attentional strategy differences were found with the slow 600 msec movement. These findings suggest that task constraints in the form of kinematic criteria, together with the perceived availability of visual information, contribute to determining attentional strategy in movement production.     

Concurrent visual feedback and spatial accuracy in continuous aiming movements

The effect of concurrent visual feedback (CVF) on continuous aiming movements was investigated in the preferred hand of participants of college age (ns = 12 men, 8 women). Participants made continuous rapid reversal movements with a lightweight lever in the sagittal plane. Participants attempted to reach a short target (20 degrees) and a long target (60 degrees) in separate constant practice conditions, but alternated between the two targets in a variable practice condition. Four blocks of practice trials were provided in each condition, with 40 movements made in each. CVF of the position-time trace was provided for the first 20 movements of each block, but was removed for the remaining 20 movements in each block. Movements were more accurate and consistent during constant practice compared to variable practice where the short target was overshot and the long target was undershot. CVF reduced errors in all conditions, compared to movements without CVF, particularly for the short target during variable practice. The results suggest that the interference generated by alternating targets can be modulated by providing visual feedback, but once the visual feedback was removed, errors increased markedly.     

Contribution of visual information to feedforward and feedback processes in rapid pointing movements

The purpose of this study was to investigate what types of visual cues may contribute to improving movement accuracy in a pointing task, and to determine in what kind of control processes these cues are involved. During the experiment, subjects had to point their finger at visual targets as accurately as possible making rapid movements. Subjects were required to perform a movement with an amplitude of 40 cm within a series of times ranging from 110 to 270 msec. Five visual feedback conditions were applied: no feedback (NF), dynamic ongoing feedback on the complete hand trajectory (CF), static error feedback on the movement end-point (EF), and two partial feedback conditions in which dynamic feedback was available from either the initial (IF) or the terminal (TF) part of the trajectory. The results showed that under the NF and IF conditions accuracy was lowest; constant error was not speed-dependent, whereas dispersion increased with movement speed. Accuracy was highest under the CF and TF conditions and was speed-dependent, as shown by both constant error and dispersion. Under the EF condition, the accuracy level was intermediate, and was also speed-dependent. The time course of performance during the series was analyzed by comparing the mean error of the first and the last five-trial blocks in the series under the three feedback conditions resulting in accuracy improvement and speed-dependence (CF, TF and EF). The block effect was significant overall, with the last block showing greatest accuracy. The block effect was found to be significant for rapid movements only under the CF and TF conditions (with a Block × Speed interaction under the CF condition), and for all movement speeds under the EF condition. But the feedback and speed effects turned out to be significant for each block. The results are discussed in terms of the interchange between ‘corrected’ ongoing responses vs ‘amended’ delayed responses within the motor regulatory processes, the preponderance of one or the other type of response being dependent on feedback availability and movement speed.     

Target location and visual feedback as variables determining accuracy of aiming movements

The accuracy of a long aiming movement was studied as a function of whether it was performed toward or away from the midline of the subject's body in the presence or absence of visual feedback. 30 right-handed, male university students (19-26 yr.) served as subjects. With movement distance and duration controlled, the mean percentage of error was 6.34% less for movements made toward the body's midline than for those performed away from the midline. The mean percentage of error was also 48% less in the presence of visual feedback than in its absence. However, contrary to our expectation, movements executed toward the body's midline were not appreciably less disrupted in the absence of visual feedback than movements performed away from the midline.     

The role of goal orientation following performance feedback

This study examined the relationship of goal orientation and performance over a series of 2 challenging performance events. After providing performance feedback on the 1st event, the authors found that the relationship between a learning goal orientation and performance remained positive for the 2nd event, the relationship between a proving goal orientation and performance diminished from a positive to a nonsignificant level, and the relationship between an avoiding goal orientation and performance remained negative. Data analysis also indicated that the relationships between the 3 goal orientation dimensions and the performance event were differentially mediated by goal setting, self-efficacy, and effort.     

Fitts’ law holds for pointing movements under conditions of restricted visual feedback

Fitts’ law robustly predicts the time required to move rapidly to a target. However, it is unclear whether Fitts’ law holds for visually guided actions under visually restricted conditions. We tested whether Fitts’ law applies under various conditions of visual restriction and compared pointing movements in each condition. Ten healthy participants performed four pointing movement tasks under different visual feedback conditions, including full-vision (FV), no-hand-movement (NM), no-target-location (NT), and no-vision (NV) feedback conditions. The movement times (MTs) for each task exhibited highly linear relationships with the index of difficulty (r² > .96). These findings suggest that pointing movements follow Fitts’ law even when visual feedback is restricted or absent. However, the MTs and accuracy of pointing movements decreased for difficult tasks involving visual restriction.     

The influence of motives and goal orientation on feedback seeking

This study examined the relationships between feedback seeking, goal orientation, performance and four motives which, though generally considered to underlie the feedback seeking process, have not previously been measured comprehensively. Both the likelihood and the number of instances of feedback seeking were measured in two samples (employees and students) in association with perceived or selfassessed above- and below-average performance. Self-assessed performance was a major predictor of feedback seeking; also influential were goal orientation and the goal orientation-performance interaction. Increased feedback seeking was associated with the desire for useful information motive, and reduced feedback seeking with the ego defence and defensive impression management motives. The desire for useful information motive mediated the influence of performance-prove goal orientation for employees, and that of a learning goal orientation for students.     

The role of visual attention in saccadic eye movements

The relationship between saccadic eye movements and covert orienting of visual spatial attention was investigated in two experiments. In the first experiment, subjects were required to make a saccade to a specified location while also detecting a visual target presented just prior to the eye movement. Detection accuracy was highest when the location of the target coincided with the location of the saccade, suggesting that subjects use spatial attention in the programming and/or execution of saccadic eye movements. In the second experiment, subjects were explicitly directed to attend to a particular location and to make a saccade to the same location or to a different one. Superior target detection occurred at the saccade location regardless of attention instructions. This finding shows that subjects cannot move their eyes to one location and attend to a different one. The results of these experiments suggest that visuospatial attention is an important mechanism in generating voluntary saccadic eye movements.     

Positive affect as informational feedback in goal pursuit

Two studies investigated the cognitive activation of a goal following a promise to complete it. Current theorizing about the impact of positive affect as informational feedback in goal pursuit suggests two contradictory conclusions: (1) positive affect can signal that sufficient progress towards a goal has been made, but also (2) positive affect can signal that commitment to a goal should be maintained. When individuals infer that significant progress toward goal achievement has been made, the goal should be deactivated, but when individuals infer that commitment to the goal should be maintained, goal activation should be increased. To determine the conditions in which positive affect leads to increased goal activation as opposed to goal deactivation, we proposed that competing goals serve as a moderator. We found that positive affect led to decreased goal activation when competing goals were present, but to increased goal activation when competing goals were absent.     

Visual control of discrete aiming movements

An experiment is reported which investigated the visual control of discrete rapid arm movements. Subjects were required to move as rapidly as possible to several target width-movement distance combinations under both visual and non-visual conditions. The movement time (MT) data were supportive of Fitts' Law in that MT was linearly related and highly correlated to the Index of Difficulty (ID). MT was also similar for different target width-distance combinations sharing the same ID value. The error rate analysis, which compared visual to non-visual perfromance, indicated that vision was only used, and to varying degrees, when MT exceeded 200 ms (3.58 ID level). There was some evidence that vision was differentially used within target width-distance combinations sharing the same ID. Estimates of endpoint variability generally reflected the results of the error rate analysis. These results do not support the discrete correction model of Fitts' Law proposed by Keele (1968).     

Effect of goal difficulty and feedback seeking on goal attainment and learning1

Abstract: This field study investigated the effect of goal difficulty and feedback seeking on goal attainment and learning in Management by Objectives (MBO) programs. Participants (n = 105) described the degree of their goal difficulty. After 6 months, they answered a questionnaire that inquired about the frequency of the feedback‐seeking and the degree of learning during the 6‐month period. Data about the extent of goal attainment were obtained from the participants’ immediate supervisors. The results indicated that goal difficulty and the frequency of feedback seeking were positively related to the degree of goal attainment and learning.     

The role of feedback, casual attributions, and self-efficacy in goal revision

An important issue in work motivation is how, when, and why individuals revise their goals up or down over time. In the current study, the authors examine feedback, causal attributions, and self-efficacy in this process. Although self-efficacy has frequently been suggested as a key explanatory variable for goal revision, its role has yet to be directly evaluated. Additionally, although attributions have been shown to influence goal revision following failure, the extent to which attributions influence goal revision following success remains unclear. In the current study, the authors address these issues by experimentally manipulating goal progress via performance feedback and tracking the resulting changes in self-efficacy and goal revision over time. In so doing, the authors also address several interpretive ambiguities present in the existing research. Results support the hypothesized model, finding that performance feedback and attributions interactively influenced self-efficacy, which in turn influenced goal revision. These results suggest that interventions targeting attributions, and self-efficacy more directly, may have meaningful influences on goal setting and pursuit, particularly following feedback.     

Information entropy analysis of discrete aiming movements

Information entropy and mutual information were investigated in discrete movement aiming tasks over a wide range of spatial (20-160 mm) and temporal (250-1250 ms) constraints. Information entropy was calculated using two distinct analyses: (1) with no assumption on the nature of the data distribution; and (2) assuming the data have a normal distribution. The two analyses showed different results in the estimate of entropy that also changed as a function of task goals, indicating that the movement trajectory data were not from a normal distribution. It was also found that the information entropy of the discrete aiming movements was lower than the task defined indices of difficulty (ID) that were selected for the congruence with Fitts' law. Mutual information between time points of the trajectory was strongly influenced by the average movement velocity and the acceleration/deceleration segments of the movement. The entropy analysis revealed structure to the variability of the movement trajectory and outcome that has been masked by the traditional distributional analyses of discrete aiming movements.