Research in Developmental Disabilities 37 (2015) 119–126
Contents lists available at ScienceDirect
Research in Developmental Disabilities
Effect of internal versus external focus of attention on implicit motor learning in children with developmental coordination disorder Tal Jarus a,*, Parisa Ghanouni a, Rachel L. Abel a, Shelby L. Fomenoff a, Jocelyn Lundberg a, Stephanie Davidson a, Sarah Caswell a, Laura Bickerton a, Jill G. Zwicker a,b,c,d a
Department of Occupational Science and Occupational Therapy, University of British Columbia, Canada Department of Pediatrics, University of British Columbia, Canada c Child & Family Research Institute, Canada d Sunny Hill Health Centre for Children, Canada b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 20 August 2014 Received in revised form 10 November 2014 Accepted 11 November 2014 Available online
Children with developmental coordination disorder (DCD) struggle to learn new motor skills. It is unknown whether children with DCD learn motor skills more effectively with an external focus of attention (focusing on impact of movement on the environment) or an internal focus of attention (focusing on one’s body movements) during implicit (unconscious) and explicit (conscious) motor learning. Purpose: This paper aims to determine the trends of implicit motor learning in children with DCD, and how focus of attention influences motor learning in children with DCD in comparison with typically developing children. Methods: 25 children, aged 8–12, with (n = 12) and without (n = 13) DCD were randomly assigned to receive instructions that focused attention externally or internally while completing a computer tracking task during acquisition, retention, and transfer phases. The motor task involved tracking both repeated and random patterns, with the repeated pattern indicative of implicit learning. Results: Children with DCD scored lower on the motor task in all three phases of the study, demonstrating poorer implicit learning. Furthermore, graphical data showed that for the children with DCD, there was no apparent difference between internal and external focus of attention during retention and transfer, while there was an advantage to the external focus of attention group for typically developing children. Conclusion: Children with DCD demonstrate less accuracy than typically developing children in learning a motor task. Also, the effect of focus of attention on motor performance is different in children with DCD versus their typically developing counterparts during the three phases of motor learning. Implications: Results may inform clinicians how to facilitate motor learning in children with DCD by incorporating explicit learning with either internal or external focus of attention within interventions. ß 2014 Elsevier Ltd. All rights reserved.
Keywords: Motor learning Developmental coordination disorder Focus of attention Implicit Computer tracking task
* Corresponding author at: Department of Occupational Science and Occupational Therapy, UBC, T-325 2211 Wesbrook Mall, Vancouver, British Columbia V6T 2B5, Canada. Tel.: +1 604 822 7392. E-mail address: [email protected] (T. Jarus). http://dx.doi.org/10.1016/j.ridd.2014.11.009 0891-4222/ß 2014 Elsevier Ltd. All rights reserved.
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T. Jarus et al. / Research in Developmental Disabilities 37 (2015) 119–126
1. Introduction Affecting 5–6% of school-age children, developmental coordination disorder (DCD) is a neuromotor disability in which a child’s motor coordination difficulties significantly interfere with activities of daily living and academic achievement (American Psychiatric Association, 2013). These children typically have difficulty with fine and/or gross motor skills, motor performance, and learning new motor skills. Due to their motor difficulties, children with DCD tend to disengage in activities and play, which can lead to social isolation, depression, and decreasing the quality of life (Candler & Meeuwsen, 2002; Kennedy-Behr, Rodger, & Mickan, 2011; Kirby, Sugden, & Edwards, 2010; Wang, Tseng, Wilson, & Hu, 2009; Zwicker, Harris, & Klassen, 2013). Motor learning is associated with practice or experience that leads to permanent changes in performance, and can be further divided into implicit and explicit learning (Schmidt & Lee, 2005). Gentile describes these two types of learning processes as occurring simultaneously during the acquisition of functional motor skills (Gentile, 1998). Explicit learning is encoded as facts or events which occur when a child consciously attempts to put into place a known movement based on the demands of a task, whereas implicit learning processes are characterized by slow development and are not under conscious control (Gentile, 1998; Zwicker & Harris, 2009). Currently, there is little known about the interaction of implicit and explicit learning during typical and atypical development. When compared to those who are typically developing, children with DCD experience notable differences in motor skill acquisition and retention (Missiuna, Mandich, Polatajko, & Malloy-Miller, 2001). They also have greater difficulties in generalizing a learned motor task (Missiuna, 1994). Previous research by Gheysen, Van Waelvelde, and Fias (2011) demonstrates that children with DCD are unable to recognize repeated sequences; however, the study by Wilson, Maruff, and Lum (2003) shows that children with DCD are capable of learning sequences using an implicit learning process. Candler and Meeuwsen (2002) also compared the implicit learning of children with and without DCD. They found that children with DCD demonstrate the ability to recognize perceptual cues and use them for performance enhancement on a computer game without explicitly expressing knowledge of the cue, which is indicative of implicit learning. Although group differences were not significant, this may be explained by the simplicity of the task that was used. Not with standing these mixed findings, recent meta analysis showed that there is a generalized deficit in motor performance and procedural learning in individuals with DCD (Wilson, Ruddock, Smits-Engelsman, Polatajko, & Blank, 2012); however, there is little information about how implicit learning affects performance during each phase of acquisition, retention, and transfer. Current practices in pediatric rehabilitation suggest that using explicit cognitive approaches are effective intervention strategies for children with DCD (Sugden, 2007). Implicit and explicit learning processes are also consistent with the principles of intrinsic and extrinsic feedback in motor learning theories (Zwicker & Harris, 2009). Some researchers have argued that calling conscious attention to task-relevant features actually impedes performance (Candler & Meeuwsen, 2002). This argument is similar to the one given for the disadvantage of focusing internally during task acquisition (internal focus of attention) (Emanuel, Jarus, & Bart, 2008; Wulf, Shea, & Lewthwaite, 2010). Physical and occupational therapists often try to direct the learners’ focus of attention to different environmental cues or body movements in order to improve motor skill acquisition. Altering the learners’ focus of attention to an external cue (focusing on the impact of the movement on the environment) as opposed to an internal cue (focusing on one’s own body movements) has shown to be more beneficial for motor skill acquisition in adults (Beilock, Carr, MacMahon, & Starkes, 2002; Edwards & Rothwell, 2011; Emanuel et al., 2008; Freedman, Maas, Caligiuri, Wulf, & Robin, 2007; Missiua, Rivard, & Bartlett, 2003; Wulf et al., 2010; Zachry, Wulf, Mercer, & Bezodis, 2005; Zentgraf & Munzert, 2009). This could be because when people consciously try to control their own movements, as with an internal focus of attention, the automatic motor process is suppressed, whereas an external focus allows the automatic process to occur implicitly (Emanuel et al., 2008; Wulf et al., 2010). An external focus of attention may also speed up learning by making the motor skill an unconscious, automatic process, and has been shown to increase accuracy of body movements (Wulf et al., 2010; Zachry et al., 2005). Limited research has been conducted on the effects of focus of attention on motor skill acquisition in typically developing children, and in children with DCD in particular. Current research demonstrates that, contrary to findings with adults, an external focus of attention in children could interfere with learning (Emanuel et al., 2008). As children might be novice learners, an internal focus of attention could be more beneficial because their automatic motor system has not yet developed (Emanuel et al., 2008). Consequently, it can be hypothesized that individuals with developmental disorders such as DCD tend to attend more internally due to their lack of experiences. However, as far as we know, no study examined the effects of focus of attention in children with DCD during each phase of motor learning. In summary, motor learning processes in children with DCD have been studied using various methods; however, further research is warranted in order to close the prominent gaps in the literature that have been identified. The main purpose of this study was to determine if children with DCD demonstrate implicit learning in each phase of motor learning in comparison to typically developing children. The secondary purpose was to determine whether an internal or external focus of attention is more beneficial for motor learning in children with DCD. It was hypothesized that children with DCD would show poorer learning under implicit learning conditions when compared to their typically developing peers. Also, we hypothesized that there would be a difference in the effects of focus of attention on the motor learning of children with and without DCD.
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2. Methods 2.1. Participants Twenty-five children participated in this study, with 12 children with DCD (the ‘‘DCD’’ group) and 13 typically developing children (the ‘‘control’’ group). Participants in this study were between the ages of 8–12 years old. They were recruited from schools and pediatric clinics in the community. 2.1.1. Inclusion criteria Children with DCD met the criteria of Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV). The Movement Assessment Battery for Children-2 (MABC-2) (Henderson, Sugden, & Barnett, 2007) was administered to confirm the presence or absence of DCD. Children at or below the 5th percentile were placed in the ‘‘DCD’’ group, while children who scored above the 25th percentile on the MABC-2 were placed in the ‘‘control’’ group. The Developmental Coordination Disorder Questionnaire (DCD-Q), a parent questionnaire, was also used to assist in confirming DCD, using the cut-off scores falling in the indicative range for the disorder (Wilson et al., 2009). 2.1.2. Exclusion criteria The Kaufman Brief Intelligence Test, 2nd Edition (KBIT-2) was administered to provide an estimate of intelligence (Kaufman & Kaufman, 1997). Children who achieved an IQ score of less than 75 were not included in the sample. In addition, any children who had a co-existing condition that may have affected their motor performance, such as cerebral palsy or autism spectrum disorders, or who did not understand English, were excluded from this study. 2.2. Measurements tools The Movement Assessment Battery for Children-2 (MABC-2) (Henderson et al., 2007) is a comprehensive test that is frequently used to identify children with DCD (Geuze et al., 2001). Standard scores from three motor domains are converted into percentiles and a total motor score, which can be used to place children in one of three categories; normal (at or above the 16th percentile), at risk (6–15th percentile) and impaired (0–5th percentile). The MABC-2 has good reliability (interrater = 0.7–0.89, test–retest = 0.75) and validity (Henderson et al., 2007). The DCD-Q is a parent report measure that has good reliability and validity, high internal consistency (a = 0.94), and high sensitivity (85%) (Wilson et al., 2009). This screening measure for identifying children with DCD was developed in Alberta and norms established for Canadian children ages 8–15 years. Cut-off scores indicate DCD, suspect for DCD, and non-DCD. The Conners ADHD DSM-IV Scale parent questionnaire (CADS-P) (Conners, 1999) is a 26-item parent questionnaire with excellent reliability and validity. It assesses the presence of attentional difficulties that correspond to the official ADD/ADHD criteria described in the DSM-IV (Conners, 1999). Because ADHD and attentional difficulties are very common in children with DCD, and attention may affect motor learning, we wanted to assess attentional skills and potentially control for it in analysis. The Kaufman Brief Intelligence Test-2 (KBIT-2) provides a quick measure of a child’s verbal and nonverbal intelligence through three subtests. This measure has high internal consistency (vocabulary = 0.94 and matrices = 0.88) and good test– retest reliability (vocabulary = 0.86–0.97 and matrices = 0.80–0.92, depending on age) (Kaufman & Kaufman, 1997). 2.3. Computer tracking task A continuous tracking computer task was used to measure the child’s ability to perform a novel motor skill. The computer program displayed a black screen with a white circle and red ball. The program controlled the movement of the white circle, whereas the participant controlled the movement of the red ball via the joystick (Boyd & Winstein, 2004). In the acquisition and retention phases, the white circle (target) moved horizontally across the screen, whereas in the transfer phase, it moved vertically. It went through a pattern of random movement, a repeated sequence, and then random movement again, each time the target crossed the screen (Fig. 1). The patterns of the repeated sequences were not revealed to the participants, thus the accuracy in performing those patterns as practice continues is indicative of implicit motor learning process (Boyd & Winstein, 2004; Siengsukon & Boyd, 2009). The length of each trial was 30 s. All of the participants were unfamiliar with the experimental task, as it was developed solely for research purposes. 2.4. Procedure The children and their parents were provided with introductory information regarding the study along with consent and assent forms upon initial contact. Ethical approval of this study was obtained by the university Behavioral Research Ethic Board (BREB). Informed assent and consent were obtained from the participants and their families, respectively, prior to and during participation in the study. The study was conducted in a private room at the university lab or at the child’s home as per parent convenience. Before beginning the task, the child was given a brief overview of the task and was given the opportunity to ask any clarifying questions. Instructions on how to operate the joystick were also provided.
[(Fig._1)TD$IG]
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Fig. 1. Diagram of tracking task.
Participants were asked to seat in front of a computer monitor, grasp a joystick, and track the moving target on the screen (Fig. 1). All participants were given the same instructions regarding the basic technique of the task; the task was to align the red ball as closely as possible with the movements of the white circle via joystick, while the program continuously assessed the accuracy of the participants’ tracking. Participants from each of the DCD and control groups were randomly assigned to either an internal (n = 5 DCD, n = 7 control) or an external (n = 7 DCD, n = 6 control) focus of attention group. The internal focus of attention group was given instructions directing them to focus their attention on the movements of their hand, wrist and arm while performing the tracking task. Participants in the external focus of attention group were given instructions to focus on the computer screen and movements of the joystick while tracking the target. Instructions were repeated every 5 trials during the acquisition phase. Data collection was conducted on four separate days within a total time period of three weeks, with each session lasting approximately 1 h. Days 1, 2, and 3 were training days (acquisition phase) and required the children to complete five blocks of the computer tracking task. Each block consisted of 10 trials, for a total of 50 trial blocks per day. Across the three days, children completed a total of 15 training blocks. On the fourth day, the children completed one block of the same task practiced during acquisition to test for retention, and one block of the transfer task to test for the ability to transfer learning (Boyd & Winstein, 2004). 2.5. Data analysis To ensure the two diagnosis groups have been assigned correctly, independent t-tests were completed on the MABC-2 and DCD-Q. Independent t-tests were also completed on the CADS and KBIT-2 to ensure that the two diagnosis groups did not differ in attention score and IQ level. The dependent variable in this study was root-mean-square-error (RMSE), which measured the difference between the target path and the path traced by the child (Boyd & Winstein, 2004). Data from the trial blocks were averaged for each day; day 1–day 3 represent the acquisition phase, day 4 represents retention phase and transfer phase. These averages were used in the analysis. Data obtained from the computer-tracking task were converted using MatLab software to a format compatible with the statistical software. Implicit learning was measured by the degree of accuracy demonstrated during the repeated sequence of the task. To investigate the main purpose of this study, the interactions between time (day 1, day 2, day 3, retention, transfer), diagnosis (DCD/control), and pattern (random/repeated) were analyzed with a three-way analysis of variance (ANOVA) with repeated measures for time and pattern. For the secondary purpose of this study, to examine the effect of focus of attention on motor learning, we performed another three-way ANOVA with variables of time (day 1, day 2, day 3, retention, transfer), diagnosis (DCD/control), and focus of attention group (internal/external focus of attention) with repeated measures for time. An intention-to-treat analysis method was used, where the ANOVA results were based on the initial ascribed practice groups. We performed post hoc tests following significant ANOVA tests using the Bonferroni procedure to test for significant differences between the means. Eta square (h2) effect size is reported, where levels are determined as small effect size: 0.01– 0.058, medium effect size: 0.059–0.137, and large effect size >0.137 (Olejnik & Algina, 2003; Stevens, 2002). SPSS Statistics, Version 19 (IBM, NY, USA) was used and statistical significance was set at p < 0.05.
3. Results 3.1. Difference between groups in clinical characteristics As expected, independent t-tests showed that there was a significant difference in the score of MABC-2 and DCD-Q between the DCD and control groups. Intelligence estimates did not differ between groups; all participants scored >75, thus ensuring that intelligence levels did not impact a participant’s ability to complete the tracking task. There was also no
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Table 1 Clinical characteristics of participants. DCD N = 12
Control N = 13
Assessment
Mean
SD
Mean
SD
MABC-2 (%ile) DCDQ KBIT-2 CADS
2.38 30.36 99.66 59.36
2.04 6.78 25.54 19.50
55.92 60.23 113.76 47.69
21.53 12.83 13.43 12.31
t
p Value
8.56 6.93 1.74 -1.78
Contents lists available at ScienceDirect
Research in Developmental Disabilities
Effect of internal versus external focus of attention on implicit motor learning in children with developmental coordination disorder Tal Jarus a,*, Parisa Ghanouni a, Rachel L. Abel a, Shelby L. Fomenoff a, Jocelyn Lundberg a, Stephanie Davidson a, Sarah Caswell a, Laura Bickerton a, Jill G. Zwicker a,b,c,d a
Department of Occupational Science and Occupational Therapy, University of British Columbia, Canada Department of Pediatrics, University of British Columbia, Canada c Child & Family Research Institute, Canada d Sunny Hill Health Centre for Children, Canada b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 20 August 2014 Received in revised form 10 November 2014 Accepted 11 November 2014 Available online
Children with developmental coordination disorder (DCD) struggle to learn new motor skills. It is unknown whether children with DCD learn motor skills more effectively with an external focus of attention (focusing on impact of movement on the environment) or an internal focus of attention (focusing on one’s body movements) during implicit (unconscious) and explicit (conscious) motor learning. Purpose: This paper aims to determine the trends of implicit motor learning in children with DCD, and how focus of attention influences motor learning in children with DCD in comparison with typically developing children. Methods: 25 children, aged 8–12, with (n = 12) and without (n = 13) DCD were randomly assigned to receive instructions that focused attention externally or internally while completing a computer tracking task during acquisition, retention, and transfer phases. The motor task involved tracking both repeated and random patterns, with the repeated pattern indicative of implicit learning. Results: Children with DCD scored lower on the motor task in all three phases of the study, demonstrating poorer implicit learning. Furthermore, graphical data showed that for the children with DCD, there was no apparent difference between internal and external focus of attention during retention and transfer, while there was an advantage to the external focus of attention group for typically developing children. Conclusion: Children with DCD demonstrate less accuracy than typically developing children in learning a motor task. Also, the effect of focus of attention on motor performance is different in children with DCD versus their typically developing counterparts during the three phases of motor learning. Implications: Results may inform clinicians how to facilitate motor learning in children with DCD by incorporating explicit learning with either internal or external focus of attention within interventions. ß 2014 Elsevier Ltd. All rights reserved.
Keywords: Motor learning Developmental coordination disorder Focus of attention Implicit Computer tracking task
* Corresponding author at: Department of Occupational Science and Occupational Therapy, UBC, T-325 2211 Wesbrook Mall, Vancouver, British Columbia V6T 2B5, Canada. Tel.: +1 604 822 7392. E-mail address: [email protected] (T. Jarus). http://dx.doi.org/10.1016/j.ridd.2014.11.009 0891-4222/ß 2014 Elsevier Ltd. All rights reserved.
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T. Jarus et al. / Research in Developmental Disabilities 37 (2015) 119–126
1. Introduction Affecting 5–6% of school-age children, developmental coordination disorder (DCD) is a neuromotor disability in which a child’s motor coordination difficulties significantly interfere with activities of daily living and academic achievement (American Psychiatric Association, 2013). These children typically have difficulty with fine and/or gross motor skills, motor performance, and learning new motor skills. Due to their motor difficulties, children with DCD tend to disengage in activities and play, which can lead to social isolation, depression, and decreasing the quality of life (Candler & Meeuwsen, 2002; Kennedy-Behr, Rodger, & Mickan, 2011; Kirby, Sugden, & Edwards, 2010; Wang, Tseng, Wilson, & Hu, 2009; Zwicker, Harris, & Klassen, 2013). Motor learning is associated with practice or experience that leads to permanent changes in performance, and can be further divided into implicit and explicit learning (Schmidt & Lee, 2005). Gentile describes these two types of learning processes as occurring simultaneously during the acquisition of functional motor skills (Gentile, 1998). Explicit learning is encoded as facts or events which occur when a child consciously attempts to put into place a known movement based on the demands of a task, whereas implicit learning processes are characterized by slow development and are not under conscious control (Gentile, 1998; Zwicker & Harris, 2009). Currently, there is little known about the interaction of implicit and explicit learning during typical and atypical development. When compared to those who are typically developing, children with DCD experience notable differences in motor skill acquisition and retention (Missiuna, Mandich, Polatajko, & Malloy-Miller, 2001). They also have greater difficulties in generalizing a learned motor task (Missiuna, 1994). Previous research by Gheysen, Van Waelvelde, and Fias (2011) demonstrates that children with DCD are unable to recognize repeated sequences; however, the study by Wilson, Maruff, and Lum (2003) shows that children with DCD are capable of learning sequences using an implicit learning process. Candler and Meeuwsen (2002) also compared the implicit learning of children with and without DCD. They found that children with DCD demonstrate the ability to recognize perceptual cues and use them for performance enhancement on a computer game without explicitly expressing knowledge of the cue, which is indicative of implicit learning. Although group differences were not significant, this may be explained by the simplicity of the task that was used. Not with standing these mixed findings, recent meta analysis showed that there is a generalized deficit in motor performance and procedural learning in individuals with DCD (Wilson, Ruddock, Smits-Engelsman, Polatajko, & Blank, 2012); however, there is little information about how implicit learning affects performance during each phase of acquisition, retention, and transfer. Current practices in pediatric rehabilitation suggest that using explicit cognitive approaches are effective intervention strategies for children with DCD (Sugden, 2007). Implicit and explicit learning processes are also consistent with the principles of intrinsic and extrinsic feedback in motor learning theories (Zwicker & Harris, 2009). Some researchers have argued that calling conscious attention to task-relevant features actually impedes performance (Candler & Meeuwsen, 2002). This argument is similar to the one given for the disadvantage of focusing internally during task acquisition (internal focus of attention) (Emanuel, Jarus, & Bart, 2008; Wulf, Shea, & Lewthwaite, 2010). Physical and occupational therapists often try to direct the learners’ focus of attention to different environmental cues or body movements in order to improve motor skill acquisition. Altering the learners’ focus of attention to an external cue (focusing on the impact of the movement on the environment) as opposed to an internal cue (focusing on one’s own body movements) has shown to be more beneficial for motor skill acquisition in adults (Beilock, Carr, MacMahon, & Starkes, 2002; Edwards & Rothwell, 2011; Emanuel et al., 2008; Freedman, Maas, Caligiuri, Wulf, & Robin, 2007; Missiua, Rivard, & Bartlett, 2003; Wulf et al., 2010; Zachry, Wulf, Mercer, & Bezodis, 2005; Zentgraf & Munzert, 2009). This could be because when people consciously try to control their own movements, as with an internal focus of attention, the automatic motor process is suppressed, whereas an external focus allows the automatic process to occur implicitly (Emanuel et al., 2008; Wulf et al., 2010). An external focus of attention may also speed up learning by making the motor skill an unconscious, automatic process, and has been shown to increase accuracy of body movements (Wulf et al., 2010; Zachry et al., 2005). Limited research has been conducted on the effects of focus of attention on motor skill acquisition in typically developing children, and in children with DCD in particular. Current research demonstrates that, contrary to findings with adults, an external focus of attention in children could interfere with learning (Emanuel et al., 2008). As children might be novice learners, an internal focus of attention could be more beneficial because their automatic motor system has not yet developed (Emanuel et al., 2008). Consequently, it can be hypothesized that individuals with developmental disorders such as DCD tend to attend more internally due to their lack of experiences. However, as far as we know, no study examined the effects of focus of attention in children with DCD during each phase of motor learning. In summary, motor learning processes in children with DCD have been studied using various methods; however, further research is warranted in order to close the prominent gaps in the literature that have been identified. The main purpose of this study was to determine if children with DCD demonstrate implicit learning in each phase of motor learning in comparison to typically developing children. The secondary purpose was to determine whether an internal or external focus of attention is more beneficial for motor learning in children with DCD. It was hypothesized that children with DCD would show poorer learning under implicit learning conditions when compared to their typically developing peers. Also, we hypothesized that there would be a difference in the effects of focus of attention on the motor learning of children with and without DCD.
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2. Methods 2.1. Participants Twenty-five children participated in this study, with 12 children with DCD (the ‘‘DCD’’ group) and 13 typically developing children (the ‘‘control’’ group). Participants in this study were between the ages of 8–12 years old. They were recruited from schools and pediatric clinics in the community. 2.1.1. Inclusion criteria Children with DCD met the criteria of Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV). The Movement Assessment Battery for Children-2 (MABC-2) (Henderson, Sugden, & Barnett, 2007) was administered to confirm the presence or absence of DCD. Children at or below the 5th percentile were placed in the ‘‘DCD’’ group, while children who scored above the 25th percentile on the MABC-2 were placed in the ‘‘control’’ group. The Developmental Coordination Disorder Questionnaire (DCD-Q), a parent questionnaire, was also used to assist in confirming DCD, using the cut-off scores falling in the indicative range for the disorder (Wilson et al., 2009). 2.1.2. Exclusion criteria The Kaufman Brief Intelligence Test, 2nd Edition (KBIT-2) was administered to provide an estimate of intelligence (Kaufman & Kaufman, 1997). Children who achieved an IQ score of less than 75 were not included in the sample. In addition, any children who had a co-existing condition that may have affected their motor performance, such as cerebral palsy or autism spectrum disorders, or who did not understand English, were excluded from this study. 2.2. Measurements tools The Movement Assessment Battery for Children-2 (MABC-2) (Henderson et al., 2007) is a comprehensive test that is frequently used to identify children with DCD (Geuze et al., 2001). Standard scores from three motor domains are converted into percentiles and a total motor score, which can be used to place children in one of three categories; normal (at or above the 16th percentile), at risk (6–15th percentile) and impaired (0–5th percentile). The MABC-2 has good reliability (interrater = 0.7–0.89, test–retest = 0.75) and validity (Henderson et al., 2007). The DCD-Q is a parent report measure that has good reliability and validity, high internal consistency (a = 0.94), and high sensitivity (85%) (Wilson et al., 2009). This screening measure for identifying children with DCD was developed in Alberta and norms established for Canadian children ages 8–15 years. Cut-off scores indicate DCD, suspect for DCD, and non-DCD. The Conners ADHD DSM-IV Scale parent questionnaire (CADS-P) (Conners, 1999) is a 26-item parent questionnaire with excellent reliability and validity. It assesses the presence of attentional difficulties that correspond to the official ADD/ADHD criteria described in the DSM-IV (Conners, 1999). Because ADHD and attentional difficulties are very common in children with DCD, and attention may affect motor learning, we wanted to assess attentional skills and potentially control for it in analysis. The Kaufman Brief Intelligence Test-2 (KBIT-2) provides a quick measure of a child’s verbal and nonverbal intelligence through three subtests. This measure has high internal consistency (vocabulary = 0.94 and matrices = 0.88) and good test– retest reliability (vocabulary = 0.86–0.97 and matrices = 0.80–0.92, depending on age) (Kaufman & Kaufman, 1997). 2.3. Computer tracking task A continuous tracking computer task was used to measure the child’s ability to perform a novel motor skill. The computer program displayed a black screen with a white circle and red ball. The program controlled the movement of the white circle, whereas the participant controlled the movement of the red ball via the joystick (Boyd & Winstein, 2004). In the acquisition and retention phases, the white circle (target) moved horizontally across the screen, whereas in the transfer phase, it moved vertically. It went through a pattern of random movement, a repeated sequence, and then random movement again, each time the target crossed the screen (Fig. 1). The patterns of the repeated sequences were not revealed to the participants, thus the accuracy in performing those patterns as practice continues is indicative of implicit motor learning process (Boyd & Winstein, 2004; Siengsukon & Boyd, 2009). The length of each trial was 30 s. All of the participants were unfamiliar with the experimental task, as it was developed solely for research purposes. 2.4. Procedure The children and their parents were provided with introductory information regarding the study along with consent and assent forms upon initial contact. Ethical approval of this study was obtained by the university Behavioral Research Ethic Board (BREB). Informed assent and consent were obtained from the participants and their families, respectively, prior to and during participation in the study. The study was conducted in a private room at the university lab or at the child’s home as per parent convenience. Before beginning the task, the child was given a brief overview of the task and was given the opportunity to ask any clarifying questions. Instructions on how to operate the joystick were also provided.
[(Fig._1)TD$IG]
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T. Jarus et al. / Research in Developmental Disabilities 37 (2015) 119–126
Fig. 1. Diagram of tracking task.
Participants were asked to seat in front of a computer monitor, grasp a joystick, and track the moving target on the screen (Fig. 1). All participants were given the same instructions regarding the basic technique of the task; the task was to align the red ball as closely as possible with the movements of the white circle via joystick, while the program continuously assessed the accuracy of the participants’ tracking. Participants from each of the DCD and control groups were randomly assigned to either an internal (n = 5 DCD, n = 7 control) or an external (n = 7 DCD, n = 6 control) focus of attention group. The internal focus of attention group was given instructions directing them to focus their attention on the movements of their hand, wrist and arm while performing the tracking task. Participants in the external focus of attention group were given instructions to focus on the computer screen and movements of the joystick while tracking the target. Instructions were repeated every 5 trials during the acquisition phase. Data collection was conducted on four separate days within a total time period of three weeks, with each session lasting approximately 1 h. Days 1, 2, and 3 were training days (acquisition phase) and required the children to complete five blocks of the computer tracking task. Each block consisted of 10 trials, for a total of 50 trial blocks per day. Across the three days, children completed a total of 15 training blocks. On the fourth day, the children completed one block of the same task practiced during acquisition to test for retention, and one block of the transfer task to test for the ability to transfer learning (Boyd & Winstein, 2004). 2.5. Data analysis To ensure the two diagnosis groups have been assigned correctly, independent t-tests were completed on the MABC-2 and DCD-Q. Independent t-tests were also completed on the CADS and KBIT-2 to ensure that the two diagnosis groups did not differ in attention score and IQ level. The dependent variable in this study was root-mean-square-error (RMSE), which measured the difference between the target path and the path traced by the child (Boyd & Winstein, 2004). Data from the trial blocks were averaged for each day; day 1–day 3 represent the acquisition phase, day 4 represents retention phase and transfer phase. These averages were used in the analysis. Data obtained from the computer-tracking task were converted using MatLab software to a format compatible with the statistical software. Implicit learning was measured by the degree of accuracy demonstrated during the repeated sequence of the task. To investigate the main purpose of this study, the interactions between time (day 1, day 2, day 3, retention, transfer), diagnosis (DCD/control), and pattern (random/repeated) were analyzed with a three-way analysis of variance (ANOVA) with repeated measures for time and pattern. For the secondary purpose of this study, to examine the effect of focus of attention on motor learning, we performed another three-way ANOVA with variables of time (day 1, day 2, day 3, retention, transfer), diagnosis (DCD/control), and focus of attention group (internal/external focus of attention) with repeated measures for time. An intention-to-treat analysis method was used, where the ANOVA results were based on the initial ascribed practice groups. We performed post hoc tests following significant ANOVA tests using the Bonferroni procedure to test for significant differences between the means. Eta square (h2) effect size is reported, where levels are determined as small effect size: 0.01– 0.058, medium effect size: 0.059–0.137, and large effect size >0.137 (Olejnik & Algina, 2003; Stevens, 2002). SPSS Statistics, Version 19 (IBM, NY, USA) was used and statistical significance was set at p < 0.05.
3. Results 3.1. Difference between groups in clinical characteristics As expected, independent t-tests showed that there was a significant difference in the score of MABC-2 and DCD-Q between the DCD and control groups. Intelligence estimates did not differ between groups; all participants scored >75, thus ensuring that intelligence levels did not impact a participant’s ability to complete the tracking task. There was also no
T. Jarus et al. / Research in Developmental Disabilities 37 (2015) 119–126
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Table 1 Clinical characteristics of participants. DCD N = 12
Control N = 13
Assessment
Mean
SD
Mean
SD
MABC-2 (%ile) DCDQ KBIT-2 CADS
2.38 30.36 99.66 59.36
2.04 6.78 25.54 19.50
55.92 60.23 113.76 47.69
21.53 12.83 13.43 12.31
t
p Value
8.56 6.93 1.74 -1.78
