environmental context affects outcome and

7/27/2019 Environmental Context Affects Outcome And

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Perceptual & Motor Skills: Motor Skills & Ergonomics

2013, 116, 3, 953-968. © Perceptual & Motor Skills 2013

ENVIRONMENTAL CONTEXT AFFECTS OUTCOME ANDKINEMATIC CHANGES AT DIFFERENT RATES DURING SKILL

LEARNING1

JENNIFER JOHNSON DIDIER

Department of Health and Kinesiology

Sam Houston State University

LI LI

Department of Health and Kinesiology

Georgia Southern University

RICHARD A. MAGILL

Department of Teaching and Learning

New York University

Summary.—Based on Gentile’s learning model, this study used a dart-throwingtask to investigate the influence of environmental context. Novice participants (N =32) were trained in one of four conditions, while measuring outcomes and kinemat-ics. The interaction of regulatory conditions (stationary/in motion) and intertrialvariability (present/absent) created four target conditions: (1) stationary with onelocation, (2) stationary with five locations, (3) moving with one movement pattern,(4) moving with five starting locations. Performance outcome (radial error) andmovement coordination (displacement of shoulder, elbow, and wrist) changes wereinvestigated during three days of practice (480 trials). Radial error scores were ana-lyzed using a 3 x 8 x 4 (Day x Trial Block x Condition) analysis of variance, repeated

measures design. The transformed cross-correlation values of the kinematic trialswere analyzed using a 3 x 3 x 4 (Joint x Day x Condition) analysis of variance,repeated measures design. Reducing the environmental context complexity of theskill (closed regulatory conditions and no inter-trial variability), decreased outcomeerrors and changed kinematics at diff erent times in the learning. The environmentalcontext influence was observed by a day x condition interaction on joint coordina-tion. Inter-trial variability had its greatest influence on coordination. The environ-mental context should be taken into consideration when evaluating and assessingskill performance during learning.

The changes that occur during the learning of a motor skill have beenexemplified in stages of learning models (Fitts & Posner, 1967; Adams,1971), but the eff ect of the environmental context, specifically identifyingregulatory conditions and inter-trial variability distinctions, has only beenaddressed in one model (Gentile, 1972; Gentile, Higgins, Miller, & Rosen,1975). Previous models have addressed the eff ects of the environment andhow learners interact with the environment as they perform skills (New-ell, 1985; Rosengren, Savelsbergh, & van der Kamp, 2003; Davids, Bennett,& Newell, 2006); however, it was Gentile’s model that was the basis of this

study. Although researchers have hypothesized that environment aff

ects1Address correspondence to Dr. Jennifer J. Didier, Department of Health and Kinesiology,Sam Houston State University, Box 2176, Huntsville, Texas, 77341 or e-mail ([email protected]).


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J. J. DIDIER, ET AL.954

both the performance outcomes and the movements used during skillacquisition (Yang & Scholz, 2005; Chow, Davids, Button, & Koh, 2008),

most studies have reported outcome and kinematic data separately.The taxonomy suggested by Gentile, et al. (1975) categorized motor

skills into one of four categories based on regulatory conditions (station-ary or in motion) and inter-trial variability (absent or present; Table 1).Regulatory conditions are defined as features in the environment that con-trol the movement strategies used to perform a skill, while inter-trial vari-ability is defined as the similarity of regulatory conditions from one trialto the next. “Closed” skills are performed when the regulatory conditionsare stationary, while “open” skills are performed when the regulatory con-

ditions in the environmental context are in motion. From the upper left-hand corner to the lower right-hand corner of Table 1, skills become morecomplex and/or more diffi cult to perform. As skill complexity increases,the addition of movement phases and characteristics does not automati-cally make the skill more diffi cult (Magill, 2007), but when the attentionaldemands of the skill increase, the task becomes both more complex andmore diffi cult to learn or to perform (Gentile, 2000). These complex skills become more diffi cult if the skill components also involve specific timingcharacteristics, and/or the external timing of the movement is based on

the action of the object, such as a moving target in the environment (Gen-tile, 2000). Specific timing characteristics occur where timing of movementinitiation is dependent on the timing of an external moving target, and/or the action of the object, such as an object to be caught. Another exam-ple would be to achieve the rhythm of the movement, such as the timingof the step, hop, and jump in the triple jump. In some instances, the exter-nal timing of the movement is driven from the action of the object. Forexample, the movement of the ball determines the timing of movementsto catch the moving object.

Gentile (1972, 2000) proposed the eff ects of environmental contextduring motor skill learning, including closed and open skills, and the

TABLE 1

REPRESENTATION OF ENVIRONMENTAL CONTEXT MANIPULATIONS CREATING FOUR SKILL CONDITIONS BASED ON REGULATORY CONDITIONS (STATIONARY VS IN MOTION), AND ABSENCE OR PRESENCE OF

INTER-TRIAL VARIABILITY (IV)

Environmental ContextInter-trial Variability

Absent (Consistent) Present (Variable)

Regulatory condition

Stationary (closed)

Closed – no IV (Condition 1)

Closed – IV (Condition 2)

In motion (open)

Open – no IV(Condition 3)

Open – IV (Condition 4)



ENVIRONMENTAL CONTEXT, SKILL LEARNING 955

absence or presence of inter-trial variability, including the attentionaldemands, movement organization, and memory representation of the

skill. Less information processing is needed for movement preparation ofskills with no inter-trial variability, because the task is the same each time.Once a learner has practiced a skill to understand the basics, the move-ment is just repeated without having to assess the changing regulatoryconditions of the environment before each trial. Visual search of the envi-ronment provides enough critical visual cues for the learner to be success-ful due to predictability of the environment. On the other hand, increasesin inter-trial variability increase demands on attentional processes andpreparation of movement organization due to the unpredictable environ-

mental context. When the target is in motion, the learner must assess fac-tors related to this movement and their own responses to produce correct behavior. As such, the schema (Schmidt, 1975) or memory representationof the skill must also be flexible enough to adapt to the changing environ-mental context. With practice, the learner is able to attend to critical cuesneeded to perform the skill in various situations, and assess which move-ments result in the best performance outcome (Chiu, Lin, Young, Lin, Hsu,Yang, et al.,). To successfully adapt to the variable action-goals with inter-trial variability, the movement pattern learned must adapt to the chang-

ing task and regulatory conditions (Gentile, 1972). As the environmentchanges, the organism must adapt (Rosengren, et al., 2003; Davids, Button,& Bennett, 2008). This indicates there will be increased variability duringlearning as the adaptable movement pattern is generated.

To evaluate how the movement pattern changes with practice, thepatterns used throughout the skill learning stages must be observed.“Coordination” is defined as the process of mastering redundant degreesof freedom (at the nerve, muscle, or synovial joint level) or as the orga-nization of the control of the motor apparatus (Bernstein, 1967). Coordi-

nation is operationally defined here as the relationship of two or moresynovial joints, body segments, limbs, etc. at any specific time (Jeansonne,2003). Coordination will change over time during diff erent stages of skillacquisition. It is important to evaluate how coordination changes tempo-rally when identifying the coordination patterns of a movement to bet-ter understand motor skill learning. These changes provide informationabout how the movements are adapted as a skill is learned, which canthen be related to the factors in the environmental context aff ecting thesechanges. Bernstein (1967), and others (Gesell, 1929; Gentile 1972, 2000;

Kugler, Kelso, & Turvey, 1980; Newell, 1985; Latash, Danion, Scholz, &Schöner, 2004; Latash, Scholz, & Schöner, 2007; Turvey, 2007) observedchanges in coordination and provided hypotheses about the coordina-tion changes that can be expected during the course of learning a com-




plex motor skill. The coordination changes may include releasing degreesof freedom (Bernstein, 1967; Higuchi, Imanaka, & Hatayama, 2002; Ko,

Challis, & Newell, 2003; Latash, et al., 2007; Chow, et al., 2008) and changesin movement variability (Latash et al., 2004, 2007; Turvey, 2007; Wagner,Buchecker, von Duvillard, & Müller, 2010; Wagner, Pfusterschmied, Klous,von Duvillard, & Müller, 2012) to increase motor control at the joints ascoordination patterns become similar to patterns observed in subjectswith large amounts of experience. Coordination changes have beenobserved previously; however, they were not related to specific changesin outcome measures during learning, rather they only identified diff er-ences in novices and experts (Newell & van Emmerik, 1989; Vereijken,

van Emmerik, Whiting, & Newell, 1992; Schorer, Baker, Fath, & Jaitner,2007; Landlinger, Lindinger, Stoggl, Wagner, & Müller, 2010; Wagner, et

al., 2010; Reinhoff , Baker, Fischer, Strauss, & Schorer, 2012; Wagner, et al.,2012). The existing research provides few examples specifically identify-ing the changes in both the outcomes and kinematics occurring for novicelearners, thus providing little basis to identify changes during initial skilllearning (Anderson & Pitcairn, 1986; Haibach, Daniels, & Newell, 2004;Yang & Scholz, 2005; Chow, et al., 2008). Some studies provide a compari-son of novice performance to expert performance (Beilock & Gray, 2012;

Schorer, Jaitner, Wollny, Fath, & Baker, 2012), and others do not identifythe experience of their participants (Edwards, Waterhouse, Atkinson, &Reilly, 2007; Edwards & Waterhouse, 2009; Lohse, Sherwood, & Healy,2010). A few studies used novice learners only to research diff erent motor behavior manipulations (Anderson & Pitcairn, 1986; Weir, & Leavitt, 1990;Chow, et al., 2008) and many studies had limited practice trials during theacquisition phase (Weir & Leavitt, 1990; Muller & Loosch, 1999; Meira &Tani, 2001; Edwards & Waterhouse, 2009; Lohse, et al., 2010; Schorer, et al.,2012). Anderson and Pitcairn (1986) concluded that wrist angle at release

during the dart throw is the single most important predictor of successand suggests the throw is under open-loop control, indicating throwersmust prepare their movements ahead of their throw. A study measuringthe outcomes of novice dart throwers indicated the participants showedgreater improvement when they were shown knowledge of results, thanfrom a skilled model (Weir & Leavitt, 1990). In the current study, the move-ments and outcomes were measured while providing outcome feedbackafter each trial.

This critical gap in the literature is addressed in this study, looking spe-

cifically at the eff ect of environmental complexity on novice dart throwers.In this study, the authors have investigated the eff ect of the environmentalcontext characteristics on performance outcome, movement patterns, andthe relationship of the two during practice of a dart-throwing skill. The




purpose of this study was to compare learning as it related to the envi-ronmental context, measured by the timing of the outcome and kinematic

changes. Previous research concluded the rate of change in the outcomesand movements occurred at diff ering time scales (Haibach, et al., 2004).Radial error and its standard deviation of dart throwing were used toassess performance outcome, while upper extremity movement patternswere used to evaluate the change of kinematics (Schorer, et al., 2012). Thisdart task was chosen because we were able to manipulate the environ-mental context, while keeping the learner stationary, which allowed com-parisons among the diff erent conditions. It was assumed that the changesin the skill observed in the outcome and in the kinematics would be influ-

enced by the environmental context, which was systematically controlledin the experimental design (van den Tillaar, 2005; Rivilla-Garcia, Grande,Sampedro, & van den Tillaar, 2011; Wagner, Pfusterschmied, van Duvil-lard, & Müller, 2011). Gentile’s model has not been previously tested bymeasuring both outcome scores and movement coordination. Changingthe environmental context features of a skill from one trial to the next ishypothesized to aff ect both the movements used to perform the skill andthe outcome performance of the skill (Yang & Scholz, 2005; Chow, et al.,2008). Based on what was found by Haibach, et al. (2004):

Hypothesis. Changes in outcome and in kinematics of dart throwingwould occur at diff erent rates for the diff erent conditions due tothe influence of the environmental context on motor skill learning.

METHOD

Participants

Thirty-two volunteers (26 women, 6 men; M age = 22.6 yr., SD = 2.6)were recruited from undergraduate classes at Louisiana State University.

The study was approved by the University’s Institutional Review Boardfor the ethical treatment of humans. All participants gave their writteninformed consent prior to participation. Only participants with limiteddart-throwing experience (fewer than three times per year) participatedin the study. All preferred the right hand for throwing and each conditionhad eight participants who were randomly assigned to one of the fourgroups in a counterbalanced distribution. Each participant trained in onlyone of the four conditions for all practice trials.

Measures

The kinematic data were used to measure the changes in the move-ment coordination that occurred with practice. Movement coordinationwas identified as the displacement pattern of the arm during the dartthrow. The changes in the movement patterns during the three days of




practice were used to evaluate how these coordination changes aff ectedthe overall performance of the tasks. Cross-correlations of the angular dis-

placement during the dart throw cycle (from the beginning to the end ofthe throw) were calculated for each joint (elbow, shoulder, and wrist) and joint-linkage (elbow-shoulder, wrist-elbow, and shoulder-wrist) to indi-cate the coordination within and between the joints over the three daysof practice. These cross-correlation calculations allowed for comparisonsof the movement patterns across time. These comparisons also indicatedwhether the participants were changing the movement pattern used acrosstime and becoming more consistent by the end of practice. These mea-sures were used to test Gentile’s (1972, 2000) movement-pattern hypoth-

eses concerning the learning of closed and open skills with and withoutinter-trial variability.

To assess performance outcomes for the four tasks, a radial error scorewas calculated for every trial. Radial error was calculated as the displace-ment from the dart to the intended target for each throw (Hancock, Butler,& Fischman, 1995). Both the rate of performance improvements and thevariability (measured as within-subjects standard deviation) of the perfor-mance were used to test the eff ects of the environmental context character-istics on performance outcomes during three days of practice.

Apparatus

A 1.22 x 1.22 m dartboard was constructed and suspended from theceiling. A Cartesian coordinate grid, printed in cm on 0.91 m x 1.22 mwhite paper, was centered on the board. The horizontal and vertical axeswere labeled as x and y, respectively, with coordinate (0, 0) in the center.The grid was used to calibrate the target location prior to data collectionand to measure the x, y coordinates of the dart location after each throw.The target was a red circle (14.5 cm in diameter) projected to the dart-

board. The target was controlled by a computer program written in Lab-VIEW (National Instruments Corp., Austin, TX) and projected through anInfocus projector onto the target board. Each participant stood 3 m fromthe board and just to the right of the projector (Fig. 1).

Eight high-definition MCam cameras with Vicon’s optical motion capturesystem (Vicon Motion Sytems, Centennial, CO) were placed in a circular pat-tern around the throwing area. Kinematic data were recorded at 120 Hz usingthis eight-camera system, which included a Sony digital video camera to col-lect video data simultaneously with the kinematic data. The Vicon 612 system

was used to collect the kinematic data and videofi

les once every 20 trials (i.e.,the 20th trial, 40th , 60th , etc.). The trials for which kinematic data were collectedare referred to in the following sections as representative kinematic trials.

Dart-throwing tasks were performed in one of four environmentalconditions: (C1) a completely closed environment with no variability; (C2)




closed environment with inter-trial variability; (C3) open environment

with no variability; and (C4) open environment with inter-trial variabil-ity. In Condition 1 (C1; closed with no variability), a target appeared in themiddle of the dartboard and remained stationary as the learner threw thedart. After recording the outcome, the target would disappear and reap-pear before the next trial. This condition was repeated for every trial, cre-ating no inter-trial variability of the regulatory condition. For Condition 2(C2; closed with inter-trial variability), a stationary target appeared in oneof five locations on the dartboard each trial, in a counterbalanced-randomorder2 (Fig. 1B). Each target location was randomly presented 32 times each

2In this condition, there were five possible target locations in which each appeared 32 timesper day in a random order. Radial error scores are reported for trial blocks and are not sorted by target location. Target location was not controlled. Each location was collected at leastonce each day with the kinematic trials; however, the target location was not necessarily thesame for all participants at collection of the kinematic trials.

FIG. 1. A. Diagram of the projector location, toe line, and dartboard. The dartboard showslocation of target for Condition 1 (Closed Task with no inter-trial variability). B. Diagram ofdartboard for the five possible target locations for Condition 2 (Closed with IV). C. Diagramof the starting location and movement path for Condition 3 (Open with no inter-trial vari-ability). D. Represents three of the five possible movement paths used on a given trial forCondition 4 (Open with inter-trial variability).

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day. The target disappeared before each trial and reappeared similar to C1;however, the participant did not know where the target would appear. For

Condition 3 (C3), the dart-throwing task was performed in an open envi-ronment (with the target in motion) and with no inter-trial variability. Thetarget appeared on the left-hand side of the dartboard and oscillated at 0.5Hz horizontally across the entire middle of the dartboard before it disap-peared (Fig 1C). For Condition 4 (C4), the dart-throwing task performedin this condition was in a completely open environment, in which the reg-ulatory conditions were target-in-motion with inter-trial variability. Simi-lar to C3, the target moved across the dartboard in a linear pattern as thelearner threw the dart; however, it appeared in one of five locations on the

dartboard and moved across the board along diff erent paths (Fig. 1D). Thestarting location of the target varied for every trial, which accounted forthe inter-trial variability in the environmental context.

Procedure

After reading the written instructions, the participant was shown thetarget projected on the dartboard, and data collection began after all ques-tions were answered and the 16 reflective markers (14 mm in diameter) wereplaced on their upper body and throwing arm. Spherical reflective mark-

ers were placed on the right wrist, left and right posterior sacro-iliac spines(PSIS), spinous process of the seventh cervical vertebrae (C7), spinous pro-cess of the tenth thoracic vertebrae (T10), the back, and left and right anteriorsuperior iliac spines (ASIS), the sternal notch (clav), and the xiphoid processof the sternum (strn). On the throwing arm, markers were also placed on theshoulder (acromio-clavicular joint), upper arm, elbow (lateral epicondyle),forearm, and hand (third metatarsal). Shoulder off set, elbow width, wristthickness, hand thickness, and body mass of each subject were measuredand recorded for the kinematic calculations. The participant was then given

a standard metal dart (22 g), which had one refl

ective marker attached justpast the tip towards the tail used to identify dart release.For all conditions, participants stood with their throwing arm at a

90o angle prior to the presentation of the target. They were instructed tothrow soon after the target appeared on the dartboard. The x and y coor-dinates of the dart landing locations were recorded each trial and laterused to calculate the outcome measures. After each throw, the participantremoved the dart from the dartboard and returned to the same markedstarting location to prepare for the next trial. The dartboard was cleared of

the projected image after each trial, and the target reappeared for the fol-lowing trial. Each participant performed 160 trials each day for three days(approximately one hour per day).

In the first two conditions, the projected image was stationary. For C3the apparatus was the same as was described above; however, the target




appeared on the far left center of the dartboard and moved along the hori-zontal axis to the far right center of the board and back to its initial starting

point at a rate of 0.5 Hz (see Fig. 1C). The maximum distance traveled bythe target was 96 cm each direction and they were instructed to hit the tar-get between 96 cm and 192 cm. The target disappeared before each trial andreappeared similar to C1 and C2; however, the participant was instructedto hit the moving target each time. For C4, the target would appear in oneof five locations and then move across the board and back to its startinglocation similar to C3 (see Fig. 1D). An accelerometer (Kistler, Amherst,NY) was placed on the back of the dartboard and programmed to stopthe target from moving as soon as the dart made contact with the board.

This allowed the participants to receive the same knowledge of results (dis-tance between the dart and the target) given to the participants in the firsttwo conditions, and allowed for an accurate measurement of the distance between the target and dart.

Analysis

Anthropometric measurements from each participant were used tocalculate the joint centers. Joint displacements were then estimated, com- bined with the static calibration data, which were used to identify anatom-ical position and zero degree angles for each joint. Upper body positiondata were calculated for every kinematic trial. The dart throws for thesetrials were normalized from the beginning of the throw (100 frames beforedart release) to the end of follow through (100 frames before and after dartrelease), a similar method to Yang and Scholz (2005). Pre-trial (first threekinematic trials within the first 60 throws) and post-trial (last three kine-matic trials within the last 60 throws) were selected for each day for dataanalysis.

In addition to the pre- and post-trials, data from the last five kinematictrials of day 3 were averaged to assess the movement pattern used at theend of practice for each participant for each joint. This averaged trial pro-vided us with the movement pattern exhibited after practice and allowedus to compare this pattern with the ones used throughout practice. Thekinematic data from the averaged trial of day 3 and the six pre- and post-trials were used in the cross-correlation calculations. Each of the pre- andpost-trials from each day were correlated with the averaged trial to assesshow similar the movements were at the beginning and end of practice, andto indicate when the changes in the movement pattern occurred. This mea-sure provided a comparison of movement patterns as well as the rate ofchange in the coordination patterns over time. These kinematic trials werealso compared to one another to assess the joint-linkage relationships. Foreach trial the elbow-wrist, wrist-shoulder, and shoulder-elbow patterns




were compared. Because cross-correlation values are not normally distrib-uted (the values ranged between –1 and +1), a Fisher Z log transformation

was performed before statistical analysis so that parametric statistics could be used.

These radial error values were then averaged in blocks of 20 trials toassess both the magnitude of the performance improvements during thethree days of practice, and the rate of these improvements. Radial errorscores and the within-subjects standard deviations in mean blocks of 20 tri-als were analyzed using a 3 (Day) x 8 (Trial Block) x 4 (Condition) analysisof variance (ANOVA), repeated measures design. The transformed cross-correlation values of the kinematic trials were analyzed using a 3 (Joint) x

3 (Day) x 4 (Condition) repeated measures ANOVA. The log transforma-tions of the joint-linkage cross-correlations across the three days were cal-culated to test if a release in the degrees of freedom was observed, andif this occurred in a proximal to distal direction. These joint-linkage data(elbow-wrist, wrist-shoulder, and elbow-shoulder) were analyzed using a 3(Joint-linkage) x 3 (Day) x 4 (Condition) repeated measures ANOVA on thetransformed data. For the kinematic trials there were two trial blocks (pre-and post-) per day. All necessary post hoc analyses were performed usingTukey’s HSD. Diff erences were considered statistically significant at α < .05.

RESULTS

Performance Outcome Scores

Both mean and standard deviation of radial errors decreased withtraining, for day and block respectively, for each condition (Table 2).

TABLE 2

MEAN RADIAL ERROR (CM) AND STANDARD DEVIATION (CM) WITH STANDARD ERRORS ACROSS THREE PRACTICE DAYS , BY CONDITION , SIGNIFICANT DIFFERENCES BETWEEN DAYS 1 AND 2 COMPARED TO DAY

3 MEANS

Condition Measure Day 1Day 1

SEDay 2

Day 2SE

Day 3Day 3

SE

Closed, no IV M 14.87 1.33 14.57 1.19 13.13 1.13

SD 8.64 1.12 8.33 0.98 7.33 0.91

Closed, IV M 14.22 1.41 12.68 1.34 11.40 0.93

SD 11.13 1.81 9.82 2.08 8.90 1.53

Open, no IV M 18.18 1.72 17.78 2.33 15.99 2.24

SD 9.68 0.94 10.15 1.34 9.16 1.27Open, IV M 19.42 3.24 17.50 2.31 14.90 1.02

SD 11.13 1.45 9.88 1.02 9.30 0.99

Note.—A mean score inside the target occurs at less than 7.25 cm. M = mean of radial errors;SD = standard deviation; SE = standard deviation of radial errors.




Kinematics

Kinematic data indicated more complex learning behavior compared tothe simple decreasing trends measured with the performance data. Cross-correlations (R) were then transformed to Fisher’s Z value in preparation

for statistical analysis to avoid the potentially skewed distribution. Thesedata revealed that Fisher Z scores (cross-correlations) changed at a diff erentrate for each of the four conditions across days (Fig. 2), i.e., there was a sta-tistically significant three-way day x joint x condition interaction (Table 3).

FIG. 2. Plots of three-way interaction, Day x Joint x Condition. Cross-correlations compar-ing displacement for each joint across three days. Conditions are C1 (closed with no inter-trialvariability, black bars), C2 (closed with inter-trial variability, light gray bars), C3 (open withno inter-trial variability, white bars), and C4 (open with inter-trial variability, dark gray bars).

TABLE 3

ANALYSIS OF VARIANCE FOR OUTCOMES AND KINEMATICS

Source df MS F p ηp2 Post hoc Comparison

Performance outcome scores

Day (M) 2 441.40 9.54 .0003 .25 Day 1 & 2 > 3

Blocks (M) 7 59.98 5.87 .0001 .17 Block 1 > 2–8

Day (SD) 2 140.08 6.75 .0002 .19 Day 1 (10.14 cm) > Day 3 (8.67 cm)

Blocks (SD) 7 31.83 2.34 .0300.07

Block 1 (12.29 cm) > Block 8 (8.13cm)

Joint cross-correlations

Day 2 17.87 40.93 .0002 .37

Joint 2 25.56 19.80 .0007 .44

Condition X DayX Joint 12 0.48 2.45 .0091 .09

Transformed joint linkage correlations

Joint linkage 2 17.87 46.07 .0001 .43 Elbow-wrist ≠ Elbow-shoulder,Shoulder-wrist





The three-way interactions illustrated in Fig. 2 present the eff ect of theenvironmental context with a unique pattern observed in each of the three bar graphs. On Days 1 and 2, similar patterns were observed for the closed

skills (C1 and C2) and open skills without inter-trial variability (C3), whilethe condition with open skills and inter-trial variability (C4) presented theopposite trend. The eff ect of the stationary target with inter-trial variabil-ity (C2) resulted in a diff erent relationship between the shoulder and wriston Day 3. These results support the link between environmental contextand movement strategies during learning, as suggested by Gentile (2000).

The analysis of the joint-linkages, using the transformed joint link-age correlation values, indicated a significant main eff ect for joint linkage(Table 3 and Fig. 3).

DISCUSSION For all four environmental conditions, outcome performance

improved across days and across trial blocks within each day, similar tothe findings of Lohse, et al. (2010). Kinematic changes were also observedacross days and joints as the movement patterns produced were less vari-able later in practice and became more consistent. Errors decreased andmovement became smoother and more focused during practice as evi-denced from the cross correlations showing diff erences across the three

days (Fig. 2); however, the timing of these two changes varied. Theseresults indicated diff erent patterns of change when comparing the envi-ronmental context to the changes in movement coordination. There was anon-linear relationship between the conditions as the statistically signifi-cant diff erences occurred between diff erent days for each measure. This

FIG. 3. Wrist angle–elbow angle plots from Days 1 and 3, showing the changes withpractice. This joint linkage presented the greatest change across the three days of practice.





suggests in each condition the learners used a diff erent source of infor-mation when learning the motor skill. Figure 3 indicates the diff erences

in movements by day of practice. There are two distinct patterns of move-ments from Day 1 to Day 3.

Learning, as evaluated by improvements in outcome scores andchanges in kinematics, occurred at diff erent times within each of the con-ditions. Statistically significant movement pattern changes were observedfrom Day 1 to 2 and Day 2 to 3 (Fig. 2), while performance outcomechanges were observed only from Day 2 to 3 (Table 2). Environmental con-text also influenced the learning process as hypothesized, evidenced by aday x condition interaction of the movement patterns at the three joints

measured. For example, inter-trial variability lead to diff erent inter-jointpatterns during Days 1 and 2 (C4) and Day 3 (C2), while kinematic diff er-ences were observed for C3 (open task without inter-trial variability) onDay 3, when compared to the other conditions (see Fig. 2).

The main results indicated that the environmental context aff ected boththe performance outcomes and the movements used during skill acquisitionalthough with diff erences in their timing (Table 2 and Fig. 2 & 3). The errormeans and standard deviations for both days and trial blocks decreased withpractice, with statistically significant decreases observed from trial Block 1 to

2, indicating large improvements occurred at the start of each day. In com-paring the joint coordination, there were significant diff erences in the cross-correlations of the movement patterns at the shoulder, elbow, and wrist,across the three days of practice and across the four conditions. The gradualincrease of the cross-correlation scores across days indicates the learners useda diff erent movement pattern later in practice than earlier in practice and thispattern became consistent and less variable, as observed in previous stud-ies (Latash, et al., 2004; Latash, et al., 2007; Wagner, et al., 2012). These obser-vations also support Gentile’s (1972, 2000) hypothesis about early stages of

learning, which posits that learners develop a general movement pattern,which is then refined based on the environmental context.

Based on previous research on motor skill learning, participant’s coor-dination should change as they learn to release their degrees of freedom ordevelop a functional synergy (Higuchi, et al., 2002; Latash, et al., 2007; Tur-vey, 2007; Wagner, et al., 2012). The joint linkage data support the devel-opment of a new functional movement pattern in which the degrees offreedom were controlled based on the coordination patterns exhibited bydata. The movement initially produced from the upper body and shoul-

der was observed to change as the participant became more skilled withpractice and began to throw with increased movement from the wrist. Theparticipants developed a new synergy to control the movement and adaptto the environmental context (Fig. 3).




The results of this study demonstrate that learning, as evaluated byperformance outcomes and kinematics, reflects diff erent aspects of the

learning process due to changes in the movements and outcomes occur-ring at diff erent rates. Furthermore, the relationship between perfor-mance and kinematics are influenced by the environmental context inwhich training occurs. As the regulatory conditions changed, from sta-tionary to in-motion, or as inter-trial variability was added to the environ-mental context of the task, non-linear changes in behavior were observedas the changes did not occur steadily across all trial blocks. These resultssuggest reducing the environmental complexity when first presenting thetask to be learned and systematically increasing this complexity. Results

of performance under diff erent environmental conditions demonstrate animprovement of performance and outcomes at diff erent rates. As we dis-cuss motor learning processes, especially the interaction between task andenvironmental context, we need to be aware that the relationship betweenthe two changes with time. The complexity of this time dependent rela-tionship warrants further investigation.

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Accepted May 22, 2013.



C o p y r i g h t o f P e r c e p t u a l & M o t o r S k i l l s i s t h e p r o p e r t y o f A m m o n s S c i e n t i f i c , L t d . a n d i t s

c o n t e n t m a y n o t b e c o p i e d o r e m a i l e d t o m u l t i p l e s i t e s o r p o s t e d t o a l i s t s e r v w i t h o u t t h e

c o p y r i g h t h o l d e r ' s e x p r e s s w r i t t e n p e r m i s s i o n . H o w e v e r , u s e r s m a y p r i n t , d o w n l o a d , o r e m a i l

a r t i c l e s f o r i n d i v i d u a l u s e .

environmental context affects outcome and

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