The effect of an external and internal focus of attention on dual-task performance.

Only a few research studies using reaction time (RT) measures have clearly shown that an external focus of attention requires fewer attentional resources than an internal focus of attention. The present experiments used combinations of auditory and motor tasks to examine the relation between the direction of the focus of attention (external/internal) and attentional demand on accuracy. Participants concurrently performed a dart throwing task and either a tone estimation task (Experiments 1 and 2) or a manual force production task (Experiments 3 and 4). In Experiment 1 with a between-subjects design there was a nonsignificant trend for spatial errors in dart throwing to be reduced when focus was directed externally, as opposed to internally, but only in the dual-task condition. In Experiment 2 with a within-subject design both the internal and external focus conditions showed reduced errors in the dual-task conditions compared with the single-task conditions. The correlations between the actual and estimated tones were strong and positive in both experiments (at least .90). In Experiment 3, focusing externally on either task resulted in better force production accuracy than did focusing internally. In Experiment 4, an external focus on either task resulted in better throwing accuracy than did an internal focus. Overall, the results are consistent with the predictions of the constrained action and conscious processing hypotheses that an external focus of attention lowers attentional demands relative to an internal focus of attention, but focus of attention effects also depend on the overall attentional demands of the tasks involved. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Effects of Changing the Focus of Attention on Accuracy, Acceleration, and Electromyography in Dart Throwing.

Research over the past 15 years or so has shown that an external focus on the effects of one's movements improves performance relative to an internal focus of attention on bodily actions. More recent research has attempted to discover how the focus of attention (FOA) influences underlying motor control processes by using kinematic and EMG measures. Research has shown that an external FOA reduces EMG activity and the co-contraction between agonist and antagonist muscle groups relative to an internal FOA. The primary goal of the current study was to determine how the FOA influences the acceleration pattern during dart throwing, providing a more complete kinematic description relative to earlier work. Twenty-four participants threw 24 darts in both an external focus condition, focusing on the flight of the dart, and an internal focus condition focusing on the elbow angle at dart release. Surface EMGs were recorded from the triceps and biceps muscles and acceleration was recorded in the X, Y, and Z axes. Accuracy was better with an external focus relative to an internal focus. There was greater acceleration in the Y and Z axes in the second half of the movement in the external focus condition relative to the internal focus condition. An external focus generated less co-contraction between muscle groups compared to the internal focus condition. Overall, the results showed that an internal FOA reduces movement efficiency relative to an external FOA.

Aiming accuracy in preferred and non-preferred limbs: implications for programing models of motor control.

Most models of motor programing contend that one can perform learned actions with different muscle groups or limbs demonstrating the concept of motor equivalence. The goal of this review is to determine the generality of this concept within the context of aiming movements performed by both preferred and non-preferred limbs. Theoretical approaches to motor programing are described, followed by a comparison of a variety of kinematic measures taken from preferred and non-preferred limbs from simple and more complex aiming tasks. In general, the support for motor equivalency is strong for one- and two-dimensional aiming tasks and for simultaneous bimanual movements, but mixed for unconstrained throwing tasks and tasks that require feedback-based corrections.

Judging joint angles and movement outcome: Shifting the focus of attention in dart-throwing.

Many research studies have shown the advantage of an external focus of attention (FOA) relative to an internal focus for motor learning and performance when the focus is explicitly instructed. The current experiments varied the FOA by asking the participants to judge either joint angles (internal probes) or spatial accuracy (external probes) following dart throws in which vision was removed. The probes were administered without prior practice (Experiment 1) or following 432 practice trials (Experiment 2). Spatial errors and trial-to-trial variability were reduced in Experiment 2 compared with Experiment 1. In both experiments, spatial errors were greater during internal probes compared with external probes or a no-probe control condition. These data suggest that the advantages of an external FOA relative to an internal FOA are not fully attributable to visual processing and that these advantages can be attained using probing questions between trials, whereas previous research has explicitly instructed the FOA.

On the advantage of an external focus of attention: a benefit to learning or performance?

Although there is general agreement in the sport science community that the focus of attention (FOA) has significant effects on performance, there is some debate about whether or not the FOA adopted during training affects learning. A large number of studies on the focus of attention have shown that subjects who train with an external FOA perform better on subsequent retention and transfer tests. However, the FOA in these studies was not experimentally controlled during testing. Therefore, the current study used a dart-throwing paradigm in which the FOA was experimentally manipulated at both acquisition and testing over very short and long training times. Performance at test, in terms of accuracy and precision, was improved by adopting an external focus at test regardless of the focus instructed during acquisition, in both Experiment 1 and 2. Although an effect of acquisition focus during testing in Experiment 2 provides some evidence that FOA affects learning, the current data demonstrate a much stronger effect for performance than learning, and stronger effects of attention on precision than accuracy. Theoretical implications of these results are discussed, but in general these data provide a more nuanced understanding of how attentional focus instructions influence motor learning and performance.

The role of attention in motor control.

Research on the focus of attention (FOA) in motor control has found a consistent advantage for focusing externally (on the effects of one's actions) compared to focusing internally (on one's body mechanics). However, most of this work has concentrated on movement outcomes, leaving open the question of how external attention changes the movement itself. Somewhat paradoxically, recent research has found that external attention also increases trial-by-trial movement variability. To explain these findings, we propose a theory of attention in motor control, grounded in optimal control theory, wherein variability is minimized along attended aspects of the movement. Internal attention thus reduces variability in individual bodily dimensions (positions and velocities of effectors), whereas external attention minimizes variability in the task outcome. Because the goal of a task defines a dimension in the movement space that is generally oblique to bodily dimensions, external attention should increase correlations among bodily dimensions while allowing their individual variances to grow. The current experiment tests these predictions in a dart-throwing task. External FOA led to more accurate performance and increased variability in the motion of the throwing arm, concomitant with stronger correlations among bodily dimensions (shoulder, elbow, and wrist positions and velocities) in a manner consistent with the task kinematics. These findings indicate a shift in the control policy of the motor system, consistent with the proposed theory. These results suggest an important role of attention as a control parameter in the regulation of the motor system, and more broadly illustrate the importance of cognitive mechanisms in motor behavior.

Blocked and alternating variable practice and unintended spatial variations in continuous aiming movements.

The main goal of the study was to test a prediction of schema theory: a wider range of variable practice would result in better transfer performance compared to a narrower range of variable practice in less-studied, continuous aiming movements. Constant and variable amplitude continuous aiming movements were investigated in the preferred hand of participants of college age (N = 32; 8 men, 24 women). Participants made continuous rapid reversal movements with a lever in the horizontal plane. Groups attempted to reach a short (20 degrees) target and a long target (either 45 degrees or 70 degrees) in separate constant-practice conditions, but alternated between the two targets in a variable practice condition. On the transfer test, participants alternated between unpracticed 10 degrees and 80 degrees targets. Four blocks of practice trials were provided in each condition, with 20 movements made in each. Movements were more accurate and consistent during constant practice compared to variable practice, with the 20 degrees-70 degrees group having greater spatial errors compared to the 20 degrees-45 degrees group. Both groups performed equally well on the novel transfer test suggesting that adequate practice variability had been provided during acquisition.

Thinking about muscles: the neuromuscular effects of attentional focus on accuracy and fatigue.

Although the effects of attention on movement execution are well documented behaviorally, much less research has been done on the neurophysiological changes that underlie attentional focus effects. This study presents two experiments exploring effects of attention during an isometric plantar-flexion task using surface electromyography (sEMG). Participants' attention was directed either externally (towards the force plate they were pushing against) or internally (towards their own leg, specifically the agonist muscle). Experiment 1 tested the effects of attention on accuracy and efficiency of force produced at three target forces (30, 60, and 100% of the maximum voluntary contraction; MVC). An internal focus of attention reduced the accuracy of force being produced and increased cocontraction of the antagonist muscle. Error on a given trial was positively correlated with the magnitude of cocontraction on that trial. Experiment 2 tested the effects of attention on muscular fatigue at 30, 60 and 100%MVC. An internal focus of attention led to less efficient intermuscular coordination, especially early in the contraction. These results suggest that an internal focus of attention disrupts efficient motor control in force production resulting in increased cocontraction, which potentially explains other neuromechanical findings (e.g. reduced functional variability with an internal focus).

Defining the focus of attention: effects of attention on perceived exertion and fatigue.

This manuscript presents two experiments designed to explore the effects of attention on perceived exertion and time to failure in a fatiguing athletic task. There were two major motivating factors for these experiments. First, there are few studies evaluating attentional focus effects in endurance tasks and, second, there is a lack of integration between studies of attentional focus as external/internal (e.g., Wulf, 2007a) compared to associative/dissociative (e.g., Stevinson and Biddle, 1998). In Experiment 1, we used a fatiguing wall-sit posture (essentially a complex, isometric task) to compare two different types of external attention with an internal focus on the position of the legs. An external focus (regardless of type) increased the time taken to failure and reduced perceived exertion. In Experiment 2, we manipulated subjects' expectancy of fatigue to test the interaction of attention and expectancy (both top-down factors) in this highly fatiguing task. Previous theories of attention during endurance tasks have suggested that as fatigue/pain increase, bottom-up factors begin to dominate subjects' attention. While this may be true, Experiment 2 showed that even in a highly fatiguing task, attentional strategies, and expectancies affected the time to failure and perceived exertion.

Neuromuscular effects of shifting the focus of attention in a simple force production task.

Research on the focus of attention has begun exploring the physiological changes that underlie the difference between internal and external foci of attention. However, previous electromyography studies have used dynamic tasks, making it difficult to interpret electrophysiological data. The authors analyzed how the focus of attention affects a subject's ability to perform an isometric force production task (focus was directed either at the force platform or the muscles responsible for force production). Subjects received practice without attentional focus instructions and then completed blocks of trials with an external and internal attentional focus separately. An external focus led to significantly less error overall and reduced surface electromyography activity with lower median power frequencies in the antagonist muscle, but attentional focus had no effects on the agonist muscle. Thus, an external focus of attention led to more efficient motor unit recruitment patterns (reduced cocontraction) and improved performance. Posttest surveys revealed subjects were aware of their improved performance with an external focus.

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.

Detecting and correcting errors in rapid aiming movements: effects of movement time, distance, and velocity.

According to closed-loop accounts of motor control, movement errors are detected by comparing sensory feedback to an acquired reference state. Differences between the reference state and the movement-produced feedback results in an error signal that serves as a basis for a correction. The main question addressed in the current study was how distance, movement time, and velocity influence both spatial or temporal error detection. Forty college-aged participants (30 women and 10 men) performed rapid aiming movements over 30 degrees or 50 degrees in either 210 ms or 350 ms without vision. The participants verbally estimated the distance moved and the movement time during acquisition before knowledge of results was given and during an immediate retention test without knowledge of results. Spatial and temporal objective-subjective correlations were greater in the 210-ms condition compared to the 350-ms condition, but were not related to movement velocity.

How changing the focus of attention affects performance, kinematics, and electromyography in dart throwing.

Research has found an advantage for an external focus of attention in motor control and learning; instructing subjects to focus on the effects of their actions, rather than on body movements, can improve performance during training and retention testing. Previous research has mostly concentrated on movement outcomes, not on the quality of the movement itself. Thus, this study combined surface electromyography (EMG) with motion analysis and outcome measures in a dart throwing task, making this the first study that includes a comprehensive analysis of changes in motor performance as a function of attentional focus. An external focus of attention led to better performance (less absolute error), decreased preparation time between throws, and reduced EMG activity in the triceps brachii. There was also some evidence of increased variability for kinematic measures of the shoulder joint under an external focus relative to an internal focus. These results suggest improved movement economy with an external focus of attention.

Concurrent Visual Feedback, Practice Organization, and Spatial Aiming Accuracy in Rapid Movement Sequences.

While the availability of visual feedback is a well-known factor influencing the accuracy of rapid aiming movements, little is known about how vision might interact with a contextual variable like practice organization. In the current study, the interaction of concurrent visual feedback (CVF) and practice organization on aiming movement accuracy was investigated in the dominant limb of 40 college-aged participants. Participants performed "triplets" of rapid aiming movements with a lightweight lever in the sagittal plane involving short (20°), medium (40°), long (60°) distances and were randomly assigned to one of four groups (n=10) in a 2 (Group: Blocked Practice, Random Practice) × 2 (Vision: CVF, no CVF) factorial design. Participants performed 24 triplets in acquisition and 10 triplets of a novel pattern (15°-45°-15°) on transfer. Movement time was controlled by a metronome set at 1.43 cycles per second resulting in a cycle time of approximately 700 ms per movement. The constant error and overall error in distance were calculated for each distance and analyzed with separate 2 (Group) × 2 (Vision) × 3 (Movement) ANOVAs with repeated measures on the last factor. When CVF was available, contextual interference effects were shown by better accuracy for the blocked practice groups during acquisition compared to the random practice group. Without CVF, participants tended to overshoot the targets and contextual interference effects were minimized during acquisition and on the first transfer trial. Random practice resulted in better transfer performance compared to blocked practice for both vision conditions when all transfer trials were included in the analysis. The findings contributed to the current literature by demonstrating the importance of practice context and visual feedback to aiming accuracy.

Parameter value switching in discrete and continuous aiming movements.

The effect of practice variations on spatial and temporal accuracy was investigated in both discrete and continuous aiming movements in the preferred hand of college-aged participants (N=25). In a completely within-subject design, participants made rapid reversal movements with a lightweight lever in the sagittal plane, practicing 20 degrees and 60 degrees movements in repeated (same distance) and alternating (switching between 20 degrees and 60 degrees) conditions. Movements were also made one at a time (discretely) or in sequences of 20 movements (continuously). Spatial constant error, spatial variable error, spatial overall error, the coefficient of variation, movement time, and the relative timing were calculated for each set of 20 movements and analyzed by within-subject analyses of variance. Movements in the repeated conditions for both discrete and continuous movements were more accurate and consistent compared to the alternating condition where the short movements were overshot and the long movements were undershot. Discrete movements were more spatially and temporally variable than continuous movements. The discrete and continuous movements showed different relative timing patterns, suggesting that the temporal structure of the motor program is affected by task characteristics.

Spatial error detection in rapid unimanual and bimanual aiming movements.

According to closed-loop accounts of motor control, movement errors are detected by comparing sensory feedback to an acquired reference state. Differences between the reference state and the movement-produced feedback results in an error signal which serves as a basis for a correction. The current study assessed whether error detection is less accurate when feedback from both hands must be analyzed compared to one hand and if error detection is more accurate in longer movements compared to shorter movements. 36 college-age participants (26 women and 10 men) performed a rapid aiming movement of varying distances with one hand or both hands simultaneously. Participants verbally estimated the distance moved on all trials before knowledge of results was given. Error detection was measured by the correlation and the mean absolute difference between the actual and estimated distance. Error detection was not more accurate for the longer movements, and participants underestimated errors in all conditions. Strong positive correlations were shown for both unimanual and bimanual aiming tasks, suggesting that two streams of sensory information can be processed concurrently.

Electromyographic control of movement time in a rapid aiming movement.

One of the major issues to emerge from research on human-limb movement is the manner in which the central nervous system regulates electromyographic (EMG) activity to produce movements that differ in duration and distance. Different models of control predict different relations between EMG characteristics and movement kinematics, particularly with regard to the role of EMG burst duration and movement time. However, models have been evaluated with means averaged over individuals and across large numbers of practice trials. The goal of this study was to assess how well individual subjects' data conform to the predictions of the control models. Participants (n = 4) performed an elbow flexion and extension task over 45 degrees in movement times between 90 and 260 msec. EMG amplitude and EMG burst duration from the right elbow flexors were correlated with movement time for each individual. As expected, movement time was positively correlated with EMG burst duration and negatively correlated with EMG amplitude, with wider ranges in the EMG burst duration-movement time correlations across participants. Data from all participants supported predictions of the impulse-timing control model, but the slopes of the studied relations varied across participants.

Generalization of error detection across motor tasks by men and women.

One of the cornerstones of the human motor learning process is the ability to self-detect and self-correct movement errors. However, despite their importance, relatively little research has been done on these topics. One unanswered question is whether error detection is a general ability or one specific to the task to be learned. To investigate this issue, 66 college-age participants (49 women and 17 men) performed four motor learning tasks: an anticipation-timing task, a slow arm-positioning task, a rapid arm-movement task (400-msec. goal), and a tone-duration production task (400-msec. goal). 50 practice trials were provided on each task, 35 with knowledge of results (KR) and 15 without KR. Participants verbally estimated error on all trials before KR was given, except for the slow positioning task on which overall error in performance was the measure of error detection. Error detection was developed for each task but transfer of this ability only occurred when two tasks shared the same movement pattern. Men performed better on anticipation-timing than women, but men and women detected errors equally well on all tasks.

Spatial assimilation effects in sequential movements: effects of parameter value switching and practice organization.

In Experiment 1, the author extended earlier work by investigating spatial assimilations in sequential aiming movements when participants were able to preplan only the 1st movement of a 2-movement sequence. Right-handed participants (N = 20) aged 18-22 years tried unimanual rapid lever reversals of 20 degrees and 60 degrees with an intermovement interval of 2.5 s. Following the 1st movement, participants made a same-distance movement, different-distance movement, or no movement in a randomly determined order. Participants overshot the short-distance target and undershot the long-distance target for both movements in the sequence, but the errors were greater when the 2nd movement differed from the 1st one. In Experiment 2, right-handed participants (N = 20) demonstrated greater assimilation effects after random practice than after blocked practice of both same-distances (20 degrees -20 degrees and 60 degrees -60 degrees ) and different-distances (20 degrees -60 degrees and 60 degrees -20 degrees ) sequences, although spatial errors were greater in different-distances conditions than in same-distances conditions. Overall, the experiments showed that parameter-value switching and practice organization are 2 major sources of spatial inaccuracy in sequential aiming movements.

Do the Principles of Motor Program Editing Apply to Longer Sequences of Rapid Aiming Movements? Part I.

Prior work had shown that performing a shorter distance aiming movement prior to a longer distance aiming movement resulted in overshooting of the short movement and undershooting of the longer movement compared to repetition of the same movement. The main question was whether the same interference effects would be found in a three-movement sequence. Right-handed (N = 24) participants (aged 18-22) produced a sequence of two or three bimanual rapid lever reversals combining short (20°) and long (60°) movements with an intermovement interval of 2.5 s beginning with either the dominant or nondominant hand. Participants overshot the short target and undershot the long target when short and long movements alternated compared to same distance control conditions, but the effects were greater for the nondominant hand. Overall, the experiment demonstrated that parameter value switching was a major source of spatial inaccuracy in sequential aiming movements.