Bradley Fawver

Too Much of a Good Thing: Random Practice Scheduling and Self-Control of Feedback Lead to Unique but Not Additive Learning Benefits

We examined the impact of self-controlled knowledge of results on the acquisition, retention, and transfer of anticipation timing skill as a function of random and blocked practice schedules. Forty-eight undergraduate students were divided into experimental groups that practiced under varying combinations of random or blocked as well as self-controlled or yoked practice conditions. Anticipation timing performance (5, 13, and 21 mph) was recorded during acquisition and during a short term no-feedback retention test. A transfer test, administered 24 h after the retention test, consisted of two novel anticipation timing speeds (9, 17 mph). Absolute error (AE) and variable error (VE) of timing served as the dependent measures. All participants improved their accuracy and consistency across acquisition blocks; however, those who practiced under blocked rather than random conditions had greater accuracy (lower AE) regardless of feedback delivery. During retention and transfer, those who practiced under random conditions showed greater consistency (lower VE) compared to their blocked counterparts. Finally, participants who controlled their feedback schedule were more accurate (lower AE) and less variable (lower VE) during transfer compared to yoked participants, regardless of practice scheduling. Our findings indicate that practicing under a random schedule improves retention and transfer consistency, while self-control of feedback is advantageous to both the accuracy and consistency with which anticipation timing skill transfers to novel task demands. The combination of these learning manipulations, however, does not improve skill retention or transfer above and beyond their orthogonal effects.

Active Control of Approach-Oriented Posture Is Influenced by Emotional Reactions

Emotions adaptively prepare the body to interact with the environment through execution of motor actions, but the extent to which emotional states modulate force control during directionally targeted movement tasks remains unknown. We sought to determine how emotions influence active control of approach-oriented posture. Participants (N = 43; 25 females) stood on a force plate and displaced their center of pressure (COP) anteriorly to a target at 50% of their maximum voluntary lean. After 7 s of real-time COP feedback, a picture representing 6 discrete categories (attack, mutilation, contamination, erotic couples, happy faces, and neutral objects) replaced the target and remained on the screen. Participants were instructed to maintain the target COP position throughout the trial. Deviation of the COP position relative to the target (root-mean-square error; RMSE) and error direction (constant error; CE) were evaluated during the feedback and picture portions of the trial. RMSE increased for all affective conditions following feedback occlusion. Following picture onset, lean error exhibited when viewing attack pictures was more anterior (i.e., greater CE) compared with the mutilation, contamination, and erotica conditions. Additionally, participants leaned more anteriorly (i.e., greater CE) during the happy faces condition compared with the mutilation and erotica conditions. Collectively, results indicate that the maintenance of an anterior COP position in the anterior direction is primarily modulated by the motivational direction of emotional stimuli.

Regulating emotions uniquely modifies reaction time, rate of force production, and accuracy of a goal-directed motor action

We investigated how emotion regulation (ER) strategies influence the execution of a memory guided, ballistic pinch grip. Participants (N=33) employed ER strategies (expressive suppression, emotional expression, and attentional deployment) while viewing emotional stimuli (IAPS images). Upon stimulus offset, participants produced a targeted pinch force aimed at 10% of their maximum voluntary contraction. Performance measures included reaction time (RT), rate of force production, and performance accuracy. As hypothesized, attentional deployment resulted in the slowest RT, largest rate of force production, and poorest performance accuracy. In contrast, expressive suppression reduced the rate of force production and increased performance accuracy relative to emotional expression and attentional deployment. Findings provide evidence that emotion regulation strategies uniquely influence human movement. Future work should further delineate the interacting role that emotion regulation strategies have in modulating both affective experience and motor performance.

Forward leaning alters gait initiation only at extreme anterior postural positions

We investigated the impact of initial body position on the displacement and velocity of center of pressure adjustments made during gait initiation. Twenty-nine healthy adults (21 ± 1y) initiated forward gait following six seconds of sustained forward posture based on percentage of their forward maximum voluntary lean (0, 5, 10, 20, 50%). Final center of pressure positions for each trial were back-calculated, as a percentage of maximum voluntary lean, using average anteroposterior constant error to the target during the last second of feedback. Scores were aggregated into percentage bands for analysis: Band 1 = -2-4.99%; Band 2 = 5-8.99%; Band 3 = 9-17.99%; Band 4 = 18-29%; Band 5 = 44-54%. Center of pressure displacement and velocity were evaluated during the decoupling, weight shift, and step initiation phases of gait initiation. Subsequent stepping parameters were also compared. During the decoupling phase, greater posterior displacement was observed in band 5 trials compared to 1, 2, and 3, and greater posterior velocity was found for band 5 compared to 1 and 3. During the weight shift phase, greater resultant displacement was found for band 5 compared to 3 and greater resultant velocity for band 5 compared to 2, 3, and 4. During step initiation, participants produced greater anterior displacement and resultant velocity during band 1, 2, and 3 compared to 5. Participants demonstrated greater swing step length and stance step time during band 5 trials compared to 3. These results suggest that only anterior postural positions greater than 44% of a persons maximum voluntary lean systematically alter spatiotemporal and kinematic indices of forward gait initiation in healthy populations. We discuss the conceptual implications of this work with respect to previous behavioral interventions.