Goal-Directed Aiming: Correcting a Force-Specification Error With the Right and Left Hands

In 2 experiments, the authors examined manual aiming asymmetries as well as the ability of participants to adjust their aiming trajectories following an unexpected change to the inertial resistance to movement. In Experiment 1, participants (N = 11) were able to rapidly adjust their movement trajectories to conform to the new movement requirements. They were faster and more consistent when aiming with their right hand than with their left hand, regardless of whether or not the movement was perturbed. In Experiment 2, participants' (N = 11) vision of the hand was manipulated so that the role of visual feedback in the corrective process could be examined. Vision had an impact not only on performance but also on the characteristics of the movement trajectories. Manual asymmetries in aiming were associated with a right hand superiority during the final corrective stages of the movement.     

Heuristic method for label placement in scatterplots

Kuhfeld (1986) has proposed several alternative scatterplot routines with labeled points. To this list is added a heuristic routine that repositions labels to eliminate overlap while attempting to maximize the number of labels presented in a metric plot.I would like to thank the reviewer of a previous version of this paper for several excellent suggestions for future modifications of both the label positioning routine and the overall plotting package.     

The effect of the Müller-Lyer illusion on the planning and control of manual aiming movements

Two experiments used Müller-Lyer stimuli to test the predictions of the planning-control model (S. Glover, 2002) for aiming movements. In Experiment 1, participants aimed to stimuli that either remained the same or changed upon movement initiation. Experiment 2 was identical except that the duration of visual feedback for online control was manipulated. The authors found that the figures visible during movement planning and online control had additive effects on endpoint bias, even when participants had ample time to use visual feedback to modify their movements (Experiment 2). These findings are problematic not only for the planning-control model but also for A. D. Milner and M. A. Goodale's (1995) two visual system explanation of illusory bias. Although our results are consistent with the idea that a single representation is used for perception, movement planning, and online control (e.g., V. H. Franz, 2001), other work from our laboratory and elsewhere suggests that the manner in which space is coded depends on constraints associated with the specific task, such as the visual cues available to the performer.     

The social-cognitive model of achievement motivation and the 2 x 2 achievement goal framework

Two studies examined hypotheses drawn from a proposed modification of the social-cognitive model of achievement motivation that centered on the 2 x 2 achievement goal framework. Implicit theories of ability were shown to be direct predictors of performance attainment and intrinsic motivation, and the goals of the 2 x 2 framework were shown to account for these direct relations. Perceived competence was shown to be a direct predictor of achievement goals, not a moderator of relations implicit theory or achievement goal effects. The results highlight the utility of attending to the approach-avoidance distinction in conceptual models of achievement motivation and are fully in line with the hierarchical model of achievement motivation.     

The effects of interval duration on temporal tracking and alternation learning

On cyclic-interval reinforcement schedules, animals typically show a postreinforcement pause that is a function of the immediately preceding time interval (temporal tracking). Animals, however, do not track single-alternation schedules-when two different intervals are presented in strict alternation on successive trials. In this experiment, pigeons were first trained with a cyclic schedule consisting of alternating blocks of 12 short intervals (5 s or 30 s) and 12 long intervals (180 s), followed by three different single-alternation interval schedules: (a) 30 s and 180 s, (b) 5 s and 180 s, and (c) 5 s and 30 s. Pigeons tracked both schedules with alternating blocks of 12 intervals. With the single-alternation schedules, when the short interval duration was 5 s, regardless of the duration of the longer interval, pigeons learned the alternation pattern, and their pause anticipated the upcoming interval. When the shorter interval was 30 s, even when the ratio of short to long intervals was kept at 6:1, pigeons did not initially show anticipatory pausing-a violation of the principle of timescale invariance.     

Nomadic inhibition of attention and motor responses

Klein and MacInnes [Klein, R. M., & MacInnes, W. J. (1999). Inhibition of return is a foraging facilitator in visual search. Psychological Science, 10, 346-352] posited that the function of a phenomenon known as the inhibition of return (IOR) [Posner, M. I., & Cohen, Y. (1984). Components of visual orienting. In H. Bouma, & D. G. Bouwhuis (Eds.), Attention and performance X: Control of language processes (pp. 531-554). Hillsdale, NJ: Erlbaum] is to facilitate the foraging of food and objects in the environment. Once a target object has been identified either the location of that target in space or a movement to that target is inhibited in order to allow the performer to shift his/her attention to something new. Interestingly, in the majority of IOR studies, participants begin their search from a central home position. This research examined IOR in a nomadic target-target paradigm in which the home position randomly appeared at one of three target locations and attentional shifts/movements progressed to other locations. In Experiment 1, participants executed simple manual button presses in response to the sequential presentation of a home position and then two target stimuli. In Experiment 2, participants made manual-aiming movements in response to the same type of presentation. Results obtained from both experiments implicate perceptual-motor mechanisms over and above the inhibition of a specific target location or response. Inhibitory effects appear to be associated with both perceptual and motor processes, and depend not only on the temporal and spatial relations between potential targets, but also on the actions required to detect or engage the targets.     

Sampling frequency and the study of eye-hand coordination in aiming

This study synchronized sampling of point of gaze (PG) and hand movements in a fast aiming task, using a 60- and a 120-Hz sampling frequency. The subjects moved eyes, head, hand, and trunk freely. For limb kinematics, a significant difference between sampling conditions was only found for the number of accelerations in the profile following peak velocity of the hand. For PG movements, no differences were found for initiation time, saccade angle, fixation duration, and overall number of saccades. However, significant differences were observed for saccade duration. Previously, an invariant feature was found for the ratio of PG and hand response times (50%). For both sampling frequencies, a significant correlation and, thus, temporal coupling was found between PG response time and time to peak acceleration for the hand. Depending on the measures required, a 60-Hz sampling of PG and hand movements may provide as meaningful results as a 120-Hz sampling.     

The role of target information on manual-aiming bias

Three experiments were conducted to examine the role of target information in manual aiming. The key manipulations in this experiment were the use of two target contexts (the two forms of the Müller-Lyer illusion) and the visual conditions under which subjects moved. In Experiment 1, we demonstrated that the inward- and outward-pointing arrows biased manual-aiming movements in a manner consistent with their well-known influence on perceptual judgements. The elimination of visual feedback during the aiming movement (Experiment 2), and visual information about the target-aiming layout prior to the movement (Experiment 3) increased the magnitude of the bias. Together, these results demonstrate the strong effect of target information on manual aiming, and specifically, on the movement-planning processes that precede movement.