University of Colorado, Boulder CU Scholar Undergraduate Honors Theses Honors Program Spring 2018 The Effects of Internal and External Focus of Attention on Balance and Dart Throwing: A Dual Task Approach Marisa A. Sobczak University of Colorado Boulder, maso5120@colorado.edu Follow this and additional works at: https://scholar.colorado.edu/honr_theses Part of the Motor Control Commons Recommended Citation Sobczak, Marisa A., "The Effects of Internal and External Focus of Attention on Balance and Dart Throwing: A Dual Task Approach" (2018). Undergraduate Honors Theses. 1551. https://scholar.colorado.edu/honr_theses/1551 This Thesis is brought to you for free and open access by Honors Program at CU Scholar. It has been accepted for inclusion in Undergraduate Honors Theses by an authorized administrator of CU Scholar. For more information, please contact cuscholaradmin@colorado.edu.
The Effects of Internal and External Focus of Attention on Balance and Dart Throwing: A Dual Task Approach By Marisa Ann Sobczak Integrative Physiology, University of Colorado Boulder April 9 th, 2018 Thesis Advisor David Sherwood, Integrative Physiology Defense Committee: David Sherwood, Integrative Physiology, Alena Grabowski, Integrative Physiology, Randolf DiDomenico, Ecology and Evolutionary Biology 1
Abstract This research study was conducted to test the effects of internal and external focus of attention (FOA) on dual motor task performance and attentional load. A balance task and dart throwing task were performed simultaneously under four different focus conditions, where the focus was directed internally or externally to each task. Balance performance was measured by the variation of position in the x-direction and the y- direction in centimeters, collected using a Wii Balance Board. Dart throwing performance was measured in terms of accuracy and consistency. After each throw the location of the dart in the x-direction and y-direction from the origin was measured in centimeters. Fifteen dart throws were made in each condition for a total of 60 trials per subject (n =28). The findings showed that there was a significant effect of FOA on dart performance, regardless of task, an external FOA resulted in superior performance relative to an internal FOA. When balancing under an external FOA an improvement in dart performance was seen, suggesting that an external FOA lowers the attentional load of the task allowing for enhanced secondary task performance. There was a lack of evidence in support of the constrained action hypothesis during the balance task. Examination on the impacts of FOA on dual motor task performance and attentional load is a fairly new area of research; further studies are required before a conclusion can be made. 2
Introduction Focus of Attention Interaction between the nervous and musculoskeletal system allows one to perform complex movements such as running and kicking a soccer ball as well as a simple balance posture. Successful motor control is a vital aspect of one s ability to effectively interact with their surroundings. An attentional focus, either an internal focus of attention (FOA) on the movement itself, or an external FOA on the outcome of the movement, has been shown to effect motor behavior. Both coaches and practitioners want to enable and enhance their athletes or patients performance. Directing an individual to mentally focus externally, towards the movement outcome, has been seen to improve performance when compared to those who were given an internally driven FOA (Wulf, 2013). This difference between an internal or external FOA can be explained by the constrained action hypothesis. This hypothesis proposes that when individuals try to consciously control their movements they inhibit their natural movements leading to decreased accuracy and efficiency. While an external FOA promotes automatic movements by directing ones focus outside of their body leading to smoother and more efficient movements. A study conducted by Wulf, Shea, and Park (2001) assessed the constrained action hypothesis with a balance task under an external and internal FOA. Rather than assigning participants to specific attentional foci groups, the researchers allowed subjects to decide which FOA enhanced their balance performance over the three-day experiment. The majority of the participants chose an external FOA after three days of practice over an internal FOA; in addition those who adopted an external FOA had superior balance 3
performance compared to those who used an internal FOA. During the post experiment interviews the subjects who performed better under an external FOA stated that it felt more natural when comparing the two attentional foci. The results of this study supported the notion that an external FOA promotes more natural movement patterns in contrast to an internal FOA. Dart Throwing Lohse, Sherwood, and Healy (2010) assessed how FOA impacted a combination of surface electromyography (EMG) and motion analyses during a dart throwing task. This study consisted of three test phases with the first phase being a practice phase and the second and third being test phases. This study was conducted with a within-subject design and directed subjects to focus on the movement of their arm (internal FOA) or on the dart board (external FOA). Their results were in line with previous research and found that an external FOA, compared to an internal FOA, resulted in improved movement accuracy and less muscular activity. Their results indicated that an external FOA not only improved accuracy during the task, but also indicated that the movements themselves were more efficient based on EMG measures and improved performance. In addition, they found that the variability of shoulder movement increased with external instructions, implying that an external FOA allows participants to perform with greater functional variability. This suggests that an external FOA allows the body to have compensatory mechanisms, which increases variability in the movement while maintaining the movement outcome rather than an internal FOA, which increases joint stiffness. 4
In another study conducted by Sherwood, Lohse, and Healy (2014) the effects of FOA on performance was studied when vision was eliminated. This experiment consisted of two testing conditions both with subjects blindfolded, the first under an external FOA condition where subjects reported where they believed the dart landed. Then they were instructed with an internal FOA where subjects reported what angle they believed their elbow was at release. The second part of this experiment tested how practice played into the effects FOA has on performance; three days of practice were provided to each subject before the participants were introduced to the experimental conditions. The results supported an external FOA is superior to an internal FOA, regardless of the experimental order. In addition, they found that an external FOA led to less error, both with and without vision, compared to an internal FOA. This research also found that practicing with an external FOA led to better accuracy during the testing phases. It was found that there was no difference between the control conditions and the external FOA group for both the mean radial error (MRE) and the bivariate variable error (BVE). The researchers believed that this was most likely due to subjects in the control condition unintentionally adopting an external FOA due to the nature of the sport, even though no focus instructions were given. A third study conducted by Sherwood, Lohse, and Healy (2016) investigated how relevant and irrelevant foci, in addition to an internal or external FOA, with and without visual feedback impacted accuracy and consistency. A relevant focus is when the focus is related to the actual task, for example, the internal-relevant task was judging one s joint angle while the external-relevant task was judging the dart release angle. While an irrelevant focus is one directed not towards the task, for example, the external-irrelevant 5
task was judging the loudness of a tone while the internal-irrelevant task was on respiration. All instructions were given while subjects participated in a dart throwing task. The results of this study were in line with previous research, that is, an external FOA led to fewer errors when compared to an internal FOA. This was found for both the relevant and irrelevant focus groups. Meaning that, judging the trajectory of the flight of the dart was better for performance when compared to judging the angle of the subject s joint. In addition focusing on the tones decreased error in dart throwing in comparison to being instructed to focus on respiration. When vision was removed, it was found that an external FOA resulted in improved accuracy; it was considered that with a lack of vision one has to recall the dartboard, increasing the demand on working memory. In combination with an internal FOA s ability to disrupt information processing systems an internal FOA resulted in poorer performance. In addition, they found that having subjects focus externally or internally on the dart throw task and removing the visual field was more significant than the relevance of the task. These three experiments examined the effects FOA had on accuracy and consistency while having subjects participate in a dart throw task. All three experiments came to the conclusion that adopting an external FOA proved to be superior when compared to an internal FOA. The researchers found that the external FOA groups were typically similar to their control groups, most likely due to the externally driven nature of the game of darts. Balance Balancing is a skill learned early on in motor behavior development and used continuously throughout adult life. The act of balancing involves a variety of 6
physiological systems including the visual, vestibular and somatosensory system (Kim, 2017). Although this particular skill requires a number of sensorimotor systems, unless there is a cognitive problem or disease present, balance should be an easy task (Wulf et al., 2007). Balance is a crucial movement for both simple and complex musculoskeletal tasks and we must stress and understand how it is impacted in order to improve performance and help practitioners. There are two common forms of balance used in research, dynamic and static balance. Dynamic balance is the act of balancing on something that is unstable, for example a stabilometer or a bosu ball. On the other hand static balance is when a person is standing on a flat non-moving surface. Both forms of balance are important and vital for human activity. Manipulation of a subject s attention has the ability to enhance or hinder this automatic movement. Shea and Wulf (1999) researched learning advantages when comparing an internal FOA and an external FOA. If subjects were instructed internally they were told to focus on their feet and if instructed externally, they were told to focus on markers on a stabilometer. It was found that instructions with an external FOA led to fewer balance errors, smoother movements, and enhanced learning on the stabilometer in comparison to an internal FOA. In another study conducted by McNevin and Wulf (2002) found that an external FOA produced better balance and secondary task performance when compared to an internal FOA. Subjects performed a standing balance task while loosely touching a hanging sheet with their fingers. The researchers did not instruct subjects to focus on the balance task but rather to focus on either trying to minimize the movement of their fingers (internal FOA) or to minimize the movements of the sheet (external FOA). It was 7
found that those who were externally instructed to reduce the movements of the sheet had better balance compared to the group instructed to focus internally by trying to reduce movements of their fingertips. A later study conducted by McNevin, Shea, and Wulf (2003) researched the effects distance had on an external FOA and balance performance. Three groups were used during the experiment, one group was instructed to focus on markers near their feet, the second instructed to focus on markers on the far inside, and the third to focus on markers on the far outside. All three groups showed improved balance and the far-inside and far-outside groups had higher-frequency movement adjustments than the near group, which implies that the farther the external focus the more natural the movements are and the better the performance. Wulf, Tollner, & Shea (2007) investigated the effects FOA had on increasing the difficulty of a balance task in a population of healthy undergraduate students. They predicted that attentional focus effects would only occur if the task were challenging enough for the subject. If the motor task is relatively simple, the subject will use previously learned automatic motor processes and will be less likely to want to diverge and won t need the benefits from an external FOA. In the first part of the experiment Wulf et al. (2007) tested two simple balance tasks. One involved standing on a flat metal surface and the other involved standing on a foam pad. The researchers considered both of these tasks to be simple balance tasks that should be a skill that does not pose a challenge for this particular population. Each subject performed both tasks under an internal FOA, an external FOA, and under no attention instructions. There was no significant interaction between FOA and postural stability while balancing on the flat 8
metal surface or while balancing on the foam pad. However, during the second part of the experiment the difficulty of the balance task was increased and resulted in a significant effect of FOA. Subjects were instructed to balance on an inflated rubber disc, first on two feet and then only on one. It was found that an external FOA significantly enhanced the postural stability for both the two-legged and one-legged task compared to the control and internal FOA. These results support that in order to see an effect of FOA on a balance task, the task must compromise postural stability to a certain degree. In a study conducted by Kim (2017) the author attempted to find how balance, with and without vision, was impacted by altering an individual s FOA while completing an intermediate yoga pose with their non-dominant leg. Balance was measured by the center of pressure (COP) in the x-direction and y-direction, and balance performance was measured by the standard deviation of these two measurements. If the subject was off center, lacking balance, there would be a larger variation in the measurements while on the other hand if the subject had superior balance there would be a smaller variation in measurements. Each subject participated in each condition; control with and without vision, an internal FOA with and without vision, and an external FOA with and without vision. Internal FOA was instructed as focus on exerting consistent muscle force on their non-dominant leg, while an external FOA instructed to focus on exerting consistent force on the Wii Balance Board. The effect of visual input was a significant factor in one s balance abilities but there was no significant effect of FOA on balance. These results do not support the previous research and the constrained action hypothesis but give us insight on what type of balance tasks to use in future studies. The task used in this experiment may have been too difficult and the attentional load required for balancing 9
too great. This didn t allow the participants to fully focus on the instructions given to them. Future experiments should aim to use a balance task that challenges an individual but does not overwhelm them, in order to observe the effects of altering ones FOA. Attentional Load The constrained action hypothesis implies that an internal FOA constrains motor systems while an external FOA allows for more natural and automatic movements. The more automatic a movement, the less attentional demands are needed for that specific task. Research in motor behavior has been interested in an individual s attentional capacity. Attentional capacity can be explained as an individual s ability to multi-task and split their attention among different tasks, before their performance suffers. Studies have investigated how a distracting task, or performing multiple tasks, have impacted motor performance. A distracting or secondary task experiment is designed to overload or stress the attentional abilities of the subject. Researchers are interested in how FOA can increase or decrease the attention needed for specific tasks and how this in turn impacts performance. It is assumed that if the secondary task performance suffers then the primary task required a large amount of attention. On the other hand, if the distractor-task required a lot of attention the performance of the primary task would suffer. According to Wulf, McNevin, and Shea (2001) the performance of a secondary task is related to the attentional demands of the primary task. They believe that poorer performance of the secondary task indicates that the primary task required a greater amount of attention. Furthermore, if according to the constrained action hypothesis an external FOA allows for more automatic movements, secondary task performance is better compared to an internal FOA. In this study, 28 students were split into FOA 10
groups, either internal or external. The primary task was to balance on a stabilometer and the participants were instructed to keep the platform in the horizontal position for as long as possible. The internal FOA group was instructed to focus their attention on their feet and try to keep them horizontal while in the external FOA group they were instructed to focus on the markers attached to the platform. The secondary task involved participants reacting to an auditory stimulus before quickly pressing a button. Results showed that under an external FOA secondary task performance was better and decreased reaction time, when compared to an internal FOA. In addition those in the external FOA group had increased balance performance in comparison to those in the internal FOA group. As discussed earlier, in a study conducted by Sherwood et al.,(2016) performance was impacted when FOA was instructed either externally or internally based on the relevance of the task, with and without visual feedback. All four instructional conditions were given while the subjects participated in a dart throwing task. Instructions for external-relevant directed subjects was to judge the dart release angle, while internalrelevant directed subjects focused on the angle of their elbow at the time of dart release. Instructions for the external-irrelevant groups had subjects rate the loudness of a tone (auditory stimuli) at the time of dart release, while those in the internal-irrelevant condition were asked to judge where they were in a breathing cycle in regards to an image given by the researchers. The results indicated that an external FOA had decreased error compared to an internal FOA, in addition, a greater advantage for the external FOA was seen during the relevant judgment conditions compared to the irrelevant conditions. Focusing on the tone detection task (external-irrelevant FOA) provided better 11
performance than focusing on the cycle of respiration (internal-irrelevant FOA). These findings suggest that focusing externally, whether on relevant or irrelevant tasks, decreased attentional load and, improved performance. In a study conducted by Kal, Kramp, and Houdijk (2013) a secondary cognitive task was added to a cyclic one-leg extension-flexion task with both the dominant and non-dominant leg. FOA was manipulated through verbal instructions. The secondary cognitive task involved a letter fluency task in which the subjects had to name as many words as they could in a certain period of time all starting with the same letter. They found that an external FOA resulted in more fluent and consistent movement execution when compared to an internal FOA. In addition, while performing the cognitive task there was significant deterioration of performance while under the internal FOA directed motor task, especially when done with the non-dominant leg. These results were in line with the constrained action hypothesis in which a motor task under an internal FOA requires more attention leading to decreased performance of the secondary task. The majority of previous studies have aimed their research on the effects FOA has on a dual-task approach when combining one motor task with one cognitive task. These studies suggest that focusing under an external FOA decreases the attention needed for that specific task, allowing attention to be directed towards another task, enhancing overall performance. However, we are interested in how FOA impacts the performance of a combination of motor tasks specifically with one task being balance. In past studies balance performance has been studied alone or with a cognitive task rather than with another motor task, even though balance plays an integral role in the success of many movements. Further understanding of how FOA can impact a combination of two motor 12
tasks, one being balance, can lead to enhancing the performance of a variety of actions. The purpose of this study is to investigate the effects FOA has on both dart throwing and balance performance using a dual task model. In addition, this study is interested in providing information on whether or not the constrained action hypothesis is supported when combining dual motor tasks. We predict that when instructed externally the variation in position in the x- direction and y-direction during the balance task will be decreased if an external FOA allows for more automatic movements requiring less attention. Therefore, there should be an increase in the variation of position in the x-direction and y-direction during the balance task when instructed internally because of an increase in attentional load. Although previous research has indicated that a more difficult task is required to need the benefits of an external FOA during a balance task (Wulf et al., 2007) we believe that the combination of a balance task with a simultaneous motor task will increase the overall task difficulty. In addition, when instructed externally on the balance task, dart throwing performance should be both more consistent and accurate due to a decrease in attentional demands in the balance task in comparison to an internal FOA. Furthermore, dart throwing performance is expected, due to previous research, to be more consistent and accurate under an external FOA compared to an internal FOA. Method Subjects Data were collected from 28 subjects (20 female, 7 male, 1 undisclosed). No dart throwing experience was required, but was self-reported through a questionnaire given the day of the experiment. Subjects were recruited from the Introduction to Statistics 13
class in the Department of Integrative Physiology at the University of Colorado Boulder. The age, gender, and ethnicity of subjects reflected the overall undergraduate student population at the University of Colorado Boulder. Subjects needed to be at least 18 years old, with no upper age limit in order to participate. Apparatus and Measurements A standard competition bristle dartboard was used and was placed 1.73 meters off the ground and 2.37 meters away from the Wii board. Participants threw regulation steel tip 21-gram darts. Performance was measured in terms of accuracy (radial error, RE), and consistency (bivariate variable error, BVE) (see Appendix Figures 9-10). The center of the dartboard was treated as the origin (point 0,0). A Wii Balance Board was used to collect balance data using software, Brainblox, developed by the Neuromechanics Laboratory in the Department of Integrative Physiology. The software provides a mode to capture, record and visualize the data provided by the Wii Balance Board. The software is compatible with Windows XP and requires a Bluetooth transceiver to connect the software to the Wii Balance Board. Four sensors in the Wii Balance Board recorded time in milliseconds once the start button was pushed. Force from sensor 1 (top left) in kilograms, force from sensor 2 (top right) in kilograms, sensor 3 (bottom left) in kilograms, and sensor 4 (bottom right) in kilograms was recorded while the program was running. Variation of position in the x-direction in centimeters and variation of position in the y-direction in centimeters and total force (the sum of the forces from all four sensors in kilograms) were obtained. Standard deviation of position in the x-direction and y-direction was calculated. 14
Procedure Upon arrival to the Motor Behavior Lab, Room 101 in Temporary Building #1 at the University of Colorado Boulder, verbal consent was obtained from each subject. Participants were asked to fill out a short survey for their height, weight, and previous dart throwing experience. Each subject participated in one practice round consisting of 6 practice throws while balancing on the Wii Balance Board with their dominant leg. Subjects were randomly assigned for which testing condition they began with. Using a Latin Square design to control for practice order, an equal number of subjects participated in each of the four practice orders. Four testing conditions were involved in this experiment; external-dart, internal-dart, external-balance, and internal-balance. Under an external-dart condition participants were instructed to mentally focus on the flight of the dart while under an internal-dart condition they were instructed to mentally focus on the angle of your elbow at the time of release. Under an external-balance condition participants were instructed to mentally focus on how even the pressure of the Wii Board is on your feet while under an internal-balance condition they were instructed to mentally focus on how stable your body sway is. At the end of every trial under every focus condition, participants were asked to give a rating of their focus on a scale of 1 to 6 using images to describe the flight of the dart, angle of elbow, pressure of the Wii board, and body sway (see Appendix Figures 11-14). Each subject participated in every testing condition and all trials were done standing on their dominant leg on the Wii Balance Board. Subjects were allowed minute rests in between trials. Fifteen throws were performed per condition, ending in a total of 60 trials per subject. 15
Experimental Design The study used a within-subject design. Each subject threw 15 darts in all four testing conditions, external-dart, internal-dart, external-balance, and internal-balance. A Wii Balance Board was used to collect data. The four sensors in the Wii Balance Board were used to measure the changes in stance in the x-direction and y-direction. The four sensors in the Wii Balance Board collected force in kilograms, and the change in stance in the x- direction and y-direction was calculated from the four sensors at a sampling rate of 1000 Hz. The variation of position indicated how balanced the subject was throughout the data collection period. If subjects were off centered during the data collection period, a larger variation of position was shown. The standard deviation in the position data in both the x- direction and y-direction were calculated. Data Analysis From the Brainblox output we obtained the variation of position in the x-direction and y- direction in centimeters over time. Each data file was trimmed for each trial, within each condition, for each subject, by using the order of the testing conditions and the previous data file as an endpoint. This was found by finding the minimum value and going back 50 timepoints (ms) from the minimum value, if the data file for that particular trial was shorter than 50 timepoints from the minimum we used the entire file. This technique minimized the size of the data file but was able to grab the dart throw snapshot for each unique subjects throwing patterns (Figure 1). A timepoint 50 ms before the minimum value to the end of the trial was used to calculate standard deviation in the y- 16
direction. The same lines were used for the x-direction corresponding to that particular trial. All standard deviations were compiled into two documents, both in the x-direction and in the y-direction. A repeated measures three-way ANOVA, 2(Task) x 2(FOA) x 15(Trial), was used to determine the effects of FOA, task, and trial on variation in position in both the x-direction and y-direction. Dart throwing performance was measured both for consistency (bivariate variable error, BVE) and accuracy (radial error, RE). The center of the board was treated as the origin (0,0) and x and y distance of where the dart landed from the center in centimeters was recorded. A repeated measures twoway ANOVA, 2(FOA) x 2(Task), was used to determine the effect of FOA and task on consistency (BVE) and accuracy (RE) of dart throws. Distance from the center y- direction (cm) 0-1 - 2-3 - 4-5 - 6-7 0 20 40 60 80 100 120 140 Time (ms) Figure 1: Microsoft Excel trace of a dart throw from Brainblox output. Results Dart Throwing Performance Figure 2 shows the mean bivariate variable error in dart throwing among all testing conditions; external FOA on the dart throw, internal FOA on the dart throw, 17
external FOA on balance, and internal FOA on balance. From Figure 2 one can see that an external FOA, regardless of task, produced less variability when compared to an internal FOA. There was a significant main effect of FOA, F(1, 27)=6.197, p=0.019, η 2 p =0.187. There was no significant main effect of task F(1, 27)=0.191, p=0.665, η 2 p =0.007. In addition there was no significant interaction between task and FOA, F(1, 27)=0.022, p=0.884, η 2 p =0.001. The statistically significant effect of an external FOA having decreased variability compared to an internal FOA allows us to reject our null hypothesis, supporting the constrained action hypothesis. Figure 3 shows the radial error in dart throwing among all testing conditions; external FOA on the dart throw, internal FOA on the dart throw, external FOA on balance, and internal FOA on balance. Figure 3 indicates that when asked to focus externally when performing a dart throw task numerically less error is apparent when compared to an internal FOA in both tasks. However, there was no significant main effect of FOA, F(1, 27)=1.043, p=0.316, η 2 p =0.037. In addition there was no significant main effect of task F(1, 27)=0.277, p=0.603, η 2 p =0.010. There was also no significant interaction between task and FOA, F(1, 27)=0.345, p=0.562, η 2 p =0.001. Due to the lack of significance we are unable to reject our null hypothesis. 18
Bivariate Variable Error 12 10 Mean (cm) 8 6 4 2 0 External FOA Dart Internal FOA Dart Condition External FOA Internal FOA Balance Balance External FOA Dart Internal FOA Dart External FOA Balance Internal FOA Balance Figure 2: Bivariate variable error for all four conditions (n=28) 12 11.5 Radial Error Mean (cm) 11 10.5 10 9.5 9 External FOA Dart Internal FOA Dart External FOA Balance Condition Internal FOA Balance External FOA Dart Internal FOA Dart External FOA Balance Internal FOA Balance Figure 3: Radial error for all four conditions (n=28) 19
Balance Performance Figure 4 depicts the average standard deviation in the x-direction for both focus conditions, external and internal FOA, and illustrates that there was little difference between the focus conditions. There was no significant effect of FOA on the variation in stance in the x-direction, F(1, 18)=0.001, p=0.771, η 2 p =0.005. Figure 5 shows the average standard deviation in the x-direction while performing both the dart throwing and balance tasks. There was slightly better balance performance when focusing on the balance task compared to the dart throwing task. However, there was no significant effect of task on variation of position in the x-direction, F(1, 18)=0.088, p=0.771, η 2 p =0.005. There was also no significant interaction between task and FOA, F(1, 18)=0.366, p=0.553, η 2 p =0.020. Figure 6 portrays the average standard deviation of position in the y-direction for both focus conditions. There was a tendency for balance performance to be better under internal focus conditions compared to external focus conditions. However, there was no significant effect of FOA on variation of position in the y-direction, F(1, 23)=0.126, p=0.726, η 2 p =0.130. Figure 7 shows average standard deviation of position in the y- direction for the two tasks that participants were asked to perform with both focus conditions. There was a tendency for balance performance to be better when focusing on the balance task compared to a focus on the dart throw task. There was a nearly significant effect of task on variation of position in the y-direction, F(1, 23)=3.439, p=0.070, η 2 p =0.008. In addition there was no significant interaction between task and FOA, F(1, 23)=0.192, p=0.666, η 2 p =0.008. However there was another nearly significant interaction between trials, task and FOA, F(8.771, 201.739)=1.500, p=0.152, η 2 p =0.061. 20
Figure 8 shows that there was a lack of change in balance performance across all trials. The lack of significance of FOA among variation of position in both the x-direction and y-direction indicates that the manipulation of focus of attention had no significant effect on the variation in balance. From this we fail to reject our null hypothesis of no effect, suggesting that the constrained action hypothesis was not supported by these data. Average Standard Deviation X Direction 0.8 0.78 0.76 0.74 0.72 0.7 0.68 0.66 0.64 Focus of Attention on Variation of Position in the X- Direction External FOA Condition Internal FOA External FOA Internal FOA Figure 4: Average Standard Deviation in the x-direction for FOA conditions regardless of task (n=28) 21
Average Standard Deviation X Direction Task on Variation of Position in the X- Direction 0.8 0.78 0.76 0.74 0.72 0.7 0.68 0.66 0.64 Balance Performance Task Dart Throwing Performance Balance Performance Dart Throwing Performance Figure 5: Average Standard Deviation of position in the x-direction for task regardless of focus condition (n=28) Average Standard Deviation Y Direction 1.95 1.9 1.85 1.8 1.75 1.7 1.65 1.6 1.55 1.5 Focus of Attention on Variation of Position in the Y- Direction External FOA Condition Internal FOA External FOA Internal FOA Figure 6: Average Standard Deviation of position in the y-direction for FOA conditions regardless of task (n=28) 22
Average Standard Deviation Y Direction 2.5 2 1.5 1 0.5 Task on Variation of Position in the Y- Direction 0 Balance Performance Task Dart Throwing Performance Balance Performance Dart Throwing Performance Figure 7: Average Standard Deviation of position in the y-direction for task regardless of focus condition (n=28) Average Standard Deviation Y Direction 2.4 2.2 2 1.8 1.6 1.4 1.2 1 Interaction between FOA, Task, and Trial: Variation of Position in the Y- Direction 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Trials External Dart Internal Dart External Balance Internal Balance Figure 8: Average Standard Deviation of position in the y-direction for three way interaction between FOA, task, and trial for all four conditions (n=28) 23
Ratings on FOA Instructions Subjects reported ratings on the flight of the dart, angle of elbow, pressure of the Wii board, and body sway at the end of each trial. The average ratings for the four conditions, external-dart, internal-dart, external-balance, and internal-balance; were 3.56, 4.16, 3.95, and 4.44 respectively. Discussion The purpose of this experiment was to investigate the effects FOA had on both dart throwing and balance performance using a dual task model. We were interested in how FOA impacts the performance and the attentional load of a combination of motor tasks specifically with one task being balance. In addition, this study was designed to determine whether or not the constrained action hypothesis was supported when combining dual motor tasks. Prior research had indicated that both dart throwing performance and balance performance should improve when instructed with an external FOA rather than an internal FOA. Similarly, previous studies have found that when performing dual tasks, when instructed with an external FOA, secondary task performance improves due to a decrease in the attentional demands of the task. The interaction between two motor tasks and the effects of FOA have not yet been clearly identified. Dart Throwing The most prominent result of the current experiment was that an external FOA, regardless of task, resulted in more consistent dart throws, which replicates what has been shown in the past. Focusing on the flight of the dart rather than on the angle of the 24
subjects elbow produced significantly less errors. As shown in previous studies (Lohse et al., 2010; Sherwood et al., 2014; Sherwood et al., 2016), they consistently found that an external FOA led to increased consistency and accuracy of dart throws compared to an internal FOA. The results of this study were similar to their findings. These results support the constrained action hypothesis (Wulf, 2013), which states that an external FOA allows for more natural movements rather than an internal FOA, which can constrain automatic movement pathways and cause greater levels of muscular cocontraction (Lohse, et al., 2010). Balance A study conducted by McNevin and Wulf (2002) found an external FOA increased postural stability compared to an internal FOA, however, unlike their study, there was no significant effect of FOA on variation of position during the balance task in this experiment. This study was unable to provide evidence in support of the constrained action hypothesis during a balance task. The lack of significance of an effect of FOA could be attributed to the simplicity of the balance task. An experiment conducted by Wulf, et al., (2007) investigated the effects FOA had on increasing the difficulty of a balance task. A balance task that was considered easy to the subjects did not produce a significant effect of FOA, conversely, as task difficulty increased an external FOA significantly enhanced postural stability. These results support that in order to see an effect of FOA during a balance task, the task should compromise postural stability. Our study did not utilize an unstable surface, which may have created too easy of a balance task for our subjects, which could have contributed to the lack of significance. However, 25
the variability scores were very consistent across trials and conditions indicating there was no evidence of fatigue and signifying the ease of the task (Figure 8). However, in the study conducted by Kim (2017) it was noted that the lack of significant effect of FOA might have been due to the extreme difficulty of the balance task. Subjects were instructed to perform and hold an intermediate yoga pose with and without vision. It was noted that participants had difficulty keeping their balance for ten seconds. Due to the difficulty of the task, subjects attentional capacity was stressed and may have compromised their ability to split their attention between task and focus instructions. Our results and the results from Wulf et al., (2007) and Kim (2017) stress the importance of the task difficulty. If the task is considered by the subjects to be easy, an individual can rely on previously learned automatic motor processes and not need the focus instructions, or if the task is too difficult the attention cannot be directed elsewhere and there will be no effect of FOA seen. From previous research and this study we can say that future experiments should use a balance task that compromises postural stability in order to see an effect of FOA. Attentional Load We aimed to test the attentional capacity of our subjects by having them perform dual motor tasks. Specifically, we were interested in how the attentional load of a balance task in combination with a motor task was impacted by an external and internal FOA. When focus was directed towards the balance task, balance performance was nearly significantly enhanced compared to when focus was directed towards the dart throw task. This suggests that balance performance may be improved when the focus is directed towards the balance task rather than the dart throw task. Yet, we did not find a significant 26
difference between balance performance while under an external FOA or an internal FOA unlike previous experiments. In the study conducted by Wulf et al., (2007) it was noted that a balance task should be challenging to the subject in order to see an impact of FOA. Our original thinking believed that the addition of a secondary motor task (dart throws) would increase the difficulty of the balance task. However, this seemed to not be the case, future studies should increase the difficulty of the balance task with a secondary task in order to see more significant results. In addition we found that dart performance was superior when under an external FOA regardless of task. When subjects were instructed with an external FOA while balancing, dart throwing was more consistent. Similar to past studies these results suggest that an external FOA lowered the attentional load of the balance task allowing for improved secondary task performance compared to an internal FOA. An external FOA is believed to lessen the attentional load of the task by allowing for more automatic movements, according to the constrained action hypothesis, leading to less attention needed for the primary task (Wulf et al., 2001). With less attention needed for performance of the primary task, a larger portion of the subjects attention can be directed towards the secondary task. Unlike an internal FOA, which constrains motor processes and requires a greater amount of attention leading to diminished performance of the secondary task. A recent study conducted by Sherwood (2018, unpublished data) investigated the effects of FOA when combining a dart throwing and a force production task. They found that the benefits of an external FOA were seen in the performance of both tasks. When instructed externally on the force production task, dart throwing performance improved 27
relative to when attention was focused internally on the force production task. On the other hand, when focused externally on the dart throwing task, performance improved compared to the internal focus condition. Similar to previous research, an external FOA was able to enhance both primary and secondary task performance compared to an internal FOA due to a decrease in the attentional load from the external FOA. Future research should continue to study dual motor task experiments in order to further understand the effects of FOA on attentional load. Conclusion Examining the predictions of the constrained action hypothesis and the effects of internal and external FOA on dual motor tasks is an unstudied area of research. Comparable to previous research an external FOA resulted in significantly fewer errors compared to an internal FOA during a dart throw task. In addition, we found that when under an external FOA, while performing a balance task, the performance of the dart task improved. Nonetheless we failed to provide enough statistically significant evidence for the constrained action hypothesis when performing dual motor tasks, further research in this area is needed before conclusions can be made. 28
References Kal, E.C., Kramp, J., & Houdijk, H. (2013). External attentional focus enhances movement automatization: A comprehensive test of the constrained action hypothesis. Human Movement Science, 32, 527-539. Kim, Eun, "The Effects of Vision and Internal and External Focus of Attention on Balance in a Yoga Pose" (2017). Undergraduate Honors Theses. 1376. Lohse, K.R., Sherwood, D.E., & Healy, A.F. (2010). How changing the focus of attention affects performance, kinematics, and electromyography in dart-throwing. Human Movement Science, 29(4), 542-555. McNevin, N.H., Shea, C.H., & Wulf, G. (2003). Increasing the distance of an external focus of attention enhances learning. Psychological Research, 67(1), 22-29. McNevin, N.H & Wulf, G. (2002). Attentional focus on supra-postural tasks affects postural control. Human Movement Science, 21(2), 187-202. Shea, C & Wulf, G. (1999). Enhancing motor learning through external-focus instructions and feedback. Human Movement Science, 18(4), 553-571. Sherwood, D.E., Lohse, K.R., & Healy, A.F. (2014). Judging Joint Angles and Movement Outcome: Shifting the Focus of Attention in Dart-Throwing. Journal of Experimental Psychology: Human Perception and Performance, 40(5), 1903-1914. Sherwood, D.E., Lohse, K.R., & Healy, A.F. (2016). Direction and Relevance of the Focus of Attention in Dart Throwing with and without Concurrent Visual Feedback. Journal of Motor Learning and Development, 4(2), 248-261. Sherwood, D.E. (2018). Unpublished Data. 29
Wulf, G. (2013). Attentional focus and motor learning: A review of 15 years. International Review of Sport and Exercise Psychology, 6(1), 77-104. Wulf, G., McNevin, N., & Shea, C.H. (2001). The automaticity of complex motor skill learning as a function of attentional focus. Quarterly Journal of Experimental Psychology, 54A, 1143-1154. Wulf, G., Shea, C.H., Park, J.H. (2001). Attention and Motor Performance: Preferences and Advantages of an External Focus. Research Quarterly for Exercise and Sport, 72(4), 335-344. Wulf, G., Tollner, T., & Shea, C.H. (2007). Attentional Focus Effects as a Function of Task Difficulty. Research Quarterly for Exercise and Sport, 78(3), 257-264. 30
Appendix RE i X i 2 Y i 2 Figure 9: radial error equation, with i the trial number. BVE 1 k i 1 k (X i X C ) 2 (Y i Y C ) 2 Figure 10: bivariate variable equation with X c and Y c the mean errors in the X and Y planes, respectively. The trial number is i, and the number of trials in block, k. Figure 11: Internaldart rating diagram Figure 12: Externaldart rating diagram 31
Figure 13: Internal-balance rating diagram Figure 14: External-balance rating diagram 32