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Steve Hansen, Spencer J. Hayes, and Simon J. Bennett

The current study examined the effect of interocular delay in a manual aiming task that required accurate end-point placement, but not precise control of a grip aperture. Participants aimed in binocular, monocular, or alternating monocular vision conditions. For the latter, 25ms monocular samples were provided to alternate eyes without delay (0ms), or a delay of 25 or 50ms. The interocular delay resulted in a longer movement time, caused by a longer time-to-peak and time-after-peak velocity, and a reduction in peak velocity. We suggest that the change in kinematics reflect a strategic response to preserve terminal aiming accuracy and variability when faced with an informational perturbation. These findings indicate that the response to the interocular delay between alternating monocular samples depends on the task-specific information used to control that behavior.

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James W. Roberts

-off between speed and accuracy ( Fitts, 1954 ; Fitts & Peterson, 1964 ). Namely, Meyer, Abrams, Kornblum, Wright, and Smith ( 1988 ) suggested primary movement endpoints assume a central tendency on or over the target center so that the majority of aims can subtend the target boundaries. In the event of an

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Shohei Shibata, Yuki Inaba, Shinsuke Yoshioka, and Senshi Fukashiro

, this study aimed to reveal the difference between the conventional and finger models in which the finger segment was considered rigid. To focus on the general function of fingers during ball throwing, this study was not conducted with a specific throwing style but aimed with throwing from a static

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Greg Wood, Samuel J. Vine, Johnny Parr, and Mark R. Wilson

predisposition to focus on the gaze of others can be exploited through the use of deceptive gaze behaviors that aim to disguise the deceiver’s future intentions ( Emery, 2000 ). Such deceptive behaviors are readily observable in sport ( Güldenpenning, Kunde, & Weigelt, 2017 ). In a sporting context, these

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James W. Roberts, Nicholas Gerber, Caroline J. Wakefield, and Philip J. Simmonds

reflected within rapid target-directed aiming, where movement times that are inversely related to physical changes in target size (i.e., longer movement times for smaller target sizes; Fitts, 1954 ; Fitts & Peterson, 1964 ) may be contrastingly immune to the perceived target size induced by the Ebbinghaus

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Samira Moeinirad, Behrouz Abdoli, Alireza Farsi, and Nasour Ahmadi

angle or a minimum of 100 ms before a critical movement in the task ( Vickers, 1996a , 1996b ). Quiet eye is associated with higher levels of skill and performance in a wide range of aiming and perceptual skills and has become a well-established characteristic of expertise and proficiency ( Lebeau et

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Esa M. Rantanen and David A. Rosenbaum

There is anecdotal evidence of drift in various reciprocal motor tasks, but as far as is known, no investigations into this phenomenon have been reported. Yet, systematic drift can potentially explain a significant proportion of the total variability in motor output. Three experiments were conducted to ascertain the nature of drift in reciprocal aiming tasks and to develop methods and measures to isolate and quantify drift for analyses. We also evaluated a computational posture-based model of reaching movements with respect to the findings of the experiments. Drift was observed in all three experiments, generally toward the middle of the joint motility range. Simulations based on the model produced drift to the middle of the task movement range rather than middle of the joint movement range. Adding noise to the model could increase its power for simulating the underlying principles of movement control as reflected in performance features such as drift.

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Michael Bohan, Mitchell G. Longstaff, Arend W.A. Van Gemmert, Miya K. Rand, and George E. Stelmach

This study examined the impact of target geometry on the trajectories of rapid pointing movements. Participants performed a graphic point-to-point task using a pen on a digitizer tablet with targets and real time trajectories displayed on a computer screen. Circular- and elliptical-shaped targets were used in order to systematically vary the accuracy constraints along two dimensions. Consistent with Fitts' Law, movement time increased as target difficulty increased. Analysis of movement kinematics revealed different patterns for targets constrained by height (H) and width (W). When W was the constraining factor, movements of greater precision were characterized by a lower peak velocity and a longer deceleration phase, with trajectories that were aimed relatively farther away from the center of the target and were more variable across trials. This indicates an emphasis on reactive, sensory-based control. When H was the constraining factor, however, movements of greater precision were characterized by a longer acceleration phase, a lower peak velocity, and a longer deceleration phase. The initial trajectory was aimed closer to the center of the target, and the trajectory path across trials was more constrained. This suggests a greater reliance on both predictive and reactive control.

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Gavin P. Lawrence, Michael A. Khan, Stuart Mourton, and Pierre-Michel Bernier

The objective of the current study was to determine whether the reliance on visual feedback that develops with practice is to due utilizing vision to adjust trajectories during movement execution (i.e., online) and/or to enhance the programming of subsequent trials (i.e., offline). Participants performed a directional aiming task with either vision during the movement, dynamic feedback of the trajectory of the movement or the movement endpoint. The full vision condition was more accurate during practice than the other feedback conditions but suffered a greater decrement in performance when feedback was removed. In addition, the reliance on trajectory feedback was greater compared with the endpoint feedback. It appears that the reliance on visual feedback that develops with practice was due to both online and offline processing.

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Patricia S. Pohl and Carolee J. Winstein

The purpose of ihis study was to compare the effects of a single practice session on performance strategies used by young and older adults to decrease movement time (MT) while maintaining accuracy of an aiming task. Five young and 5 older adult males practiced until each accumulated 500 target hits in each of two complexity conditions as defined by Fitts’s law. Participants decreased MT with practice; however, older adults had longer MTs than the young, particularly in the high-complexity condition. With practice in the low-complexity condition, participants decreased absolute acceleration and deceleration times but maintained the relative amount of MT devoted to temporal phases. In contrast, with practice in the high-complexity condition, participants decreased absolute deceleration and dwell time and changed the temporal structure. Results suggest that older adults can decrease MT with practice and that the performance strategies adopted to speed performance are more a function of task complexity than age.