Aprendizaje Motor Winstein

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1991; 71:140-149.PHYS THER.Carolee J WinsteinImplications for Physical Therapy

Knowledge of Results and Motor Learning

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Movement Science SeriesKnowledge of Results and MotorImplications for Physical Therapy Learning-

Relevant t o this special series o n mo vem ent science, a brief overview o f research intheJieId of mo tor learning is provided. A distinction between learn ing a n d pe@or-man ce is emphasized with respect to experimental d e s i e a nd the evaluation oflaboratory an d clinical intervention techniques. Intrinsic a nd extrinsic eedbackare de fn ed Basic principles of mo tor learning pertaining t o the use of aug -men tedjee dba ck or kno wledge of results (KR) are reviewed. Particula r emphasis isplaced o n recent research regarding the effects of selected KR variations (HZ rela-tive frequency, bandwidth KR, an d KR delay) on motor p e r fo m n c e an d learningi n healthy yo un g adults. Results a re discussed i n terms of short-lasting tempo rarypet$ormance effects a n d relatively long-lasting lea rnin g effects. Theoretical a n dpractical imp lications r om this research are dkcussed. It is suggested that it is up-propriate to use the principles obtained through laboratory experimentation asguidelines rather than as exact reco mmen dations when applying basic researchw i n g s o clinical practice. /Winstein CJ Knowledge of results an d m otor learn-ing-imp lications for physical therapy. P@s Ther 1991;71:140-149.1KeyWords: Feedback, Lea rning, Motor skills,


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ing of KII relative frequency, band-width KR , and KR delay. Clinicalimplications from this research forthe practice of physical therapy willbe addressed.Before reviewing the KR research, itis necessary to first make a distinctionbetween motor learning and motorcontrol. Second, to better familiarizethe reader with the field of motorlearning, a brief overview is providedof recent and future directions of re-search within this domain. Finally,consideration is given to the potentialrelevance of motor learning researchto physical therapy.Research in Motor LearningSchmidt defines motor control as "anarea of study dealing with the under-standing of the neural, physical, andbehavioral aspects of movement"13@l~and motor learning as "an area ofstudy focusing on the acquisition ofskilled movements as a result ofpractice."13@17) pace does not permita detailed discussion of the history ofmotor learning research, nor wouldsuch an excursion be particularly ger-maine to the main focus of this article.The interested reader should refer tothe work of Schmidtlj and Christina15for more detailed discussions. Tomore fully appreciate the research par-adigms and theoretical perspectivesunderlying research in motor learning,in general, and in KR, in particular,one must consider the important influ-ence of the parent discipline ofpsychology.During what has been referred to asthe "task-approach" period, fromabout 1940 through the late 1950s,research in motor learning was moti-vated primarily by the dominantstimulus-response (S-R) formulationprevalent in behavioral psychology atthat time. Research during that periodused real-world motor tasks, and theemphasis was on performance out-comes. Since the late 1960s, motorlearning research has been dominatedby the information-processing ap-proach prevalent in cognitive psychol-ogy (see article by Light16 in this spe-cial series on movement science for

further discussion of the information-processing view). The focus of thisapproach was more on the cognitiveprocesses underlying skill acquisitionthan on outcomes. To better focus onthe information-processing operationsduring motor skill acquisition, simplemotor tasks, such as those involvingthe linear slide or positioning appara-tus, were generally used. This "pro-cess approach," in contrast to the taskapproach, was strongly advocated bypsychologists such as Pew1' andAdamslHas a necessary step towardthe development of a general theoryof motor learning.In 1971, prompted by the growingbody of research in motor learningand the availability of a relatively largeempirical database from linear posi-tioning tasks, AdamslB ntroduced thefirst theory of motor learning. Invok-ing a cybernetics model, Adams pro-posed the closed-loop theory of mo-tor learning in which the motorresponse is seen primarily as drivenby feedback from the moving limb.Later, allowing for the principles ofopen-loop control in which the re-sponse is controlled primarily by amotor program, Schmidt" proposedthe schema theory of discrete motorlearning. Both Adams's and Schmidt'stheoretical contributions stimulatedsubstantial basic and applied researchactivity.20With regard to future directions formotor learning research, SchmidtZ1has advocated a return to the task ap-proach and has emphasized both thetheoretical and practical (eg, applied)contributions of such an approach.Christina15 similarly advocates inde-pendent, but cooperative, endeavorsat the basic and applied research lev-els. He suggests the need to extendresearch into the applied areas ofhealth with an emphasis on gerontol-ogy and physical rehabilitation.Motor Learning andPhysical TherapyThe shift away from applied motorlearning research during the"process-approach" period has re-cently been a source of debate in the

physical education community. Someargue that motor learning research ismeaningful for physical educationpra~titioners,~~hereas others arguethat motor learning research is notrelevant to the needs and interests ofmotor skill teachers.23A similar argu-ment could be raised with respect tothe relevance of motor learning re-search to physical therapy.Motor learning research has focusedprimarily on healthy individuals learn-ing novel motor skills (see Mulder2"for an exception). Although directapplication of the principles of motorlearning obtained through laboratoryresearch may not be immediately pos-sible, a considerable foundation hasbeen established that may be usefulto physical therapy once the properboundary conditions are established.For example, research from the mo-tor skills literature pertaining to theuse of augmented feedback could beused to provide guidelines for physi-cal therapy rehabilitation protocols.How often should the therapist pro-vide feedback during a treatment ses-sion? What kind of feedback is bestfor motor learning? The knowledgebase in motor learning can be used toprovide at least partial answers tothese and numerous other clinicallyrelevant questions.Certainly, when viewed within thebroader context of movement science,many-if not most-of the practicesof physical therapy involve some formof movement training o r reeducation(eg, back education programs, post-stroke gait training). Likewise, patientsparticipating in these various physicaltherapy programs are involved insome form of movement learning orrelearning. If we assume that the prin-ciples of motor learning gleanedthrough research with healthy sub-jects may be similar to those of motorlearning for our patients with ortho-pedic and neurologic disorders, itcould be argued that knowledge ofthese principles becomes highly rele-vant to the science and practice ofphysical therapy.Several individuals recognized therelevance of motor learning research

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to physical therapy over 20 yearsag0.~53OOne might ask why this valu-able integration was never more fullydeveloped. One explanation may bethat in an attempt to more clearly de-fine its own domain, the physicaltherapy profession turned inward and,in so doing, disassociated itself fromrelated, but nonclinical, fields. Now,there is increasing evidence that thependulum has begun its backswing.Feedback and Knowledgeof ResultsIn general, sensory information asso-ciated with motor behavior can bedivided into two major categories dis-tinguished by their temporal relation-ship with the action. Sensory informa-tion available prior to the action maybe considered asfeedfornard andincludes information related to theenvironment and the performer withrespect to the upcoming action. Incontrast to feedforward,feedback issensory information that is availableduring o r after the action. Feedbackincludes information related to thesensations associated with the move-ment itself (eg, feel, sound) as well asinformation related to the result ofthe action with respect to the environ-mental goal. These two sources offeedback have been referred to asintrinsic and extrinsic, respectively.31Intrinsic feedback is inherent to theaction and includes kinesthetic, visual,cutaneous, vestibular, and auditorysignals collectively termed "response-produced feedback."l3 These normalsources of intrinsic feedback may beabsent or damaged in the patient withcertain peripheral or central lesions.In contrast to intrinsic feedback, ex-trinsic feedback is information pro-vided from an external source and issupplemental to the intrinsic sourcesmentioned above. Extrinsic, or aug-mented, feedback can be provided tothe performer in various ways. It canbe verbal or nonverbal, and it can beprovided concurrently, immediatelyfollowing, or delayed in time withrespect to the relevant action.Extrinsic feedback relating to the out-come of an action with respect to the

environmental goal is referred to asKR. Consider the following clinicalexample. The goal is to rise from asitting position to a standing positionin a given amount of time. At the ter-mination of the trial, KR might begiven in terms of the amount of timeit took to complete the task (eg, 1.25seconds). In comparison, extrinsicfeedback, which provides informationabout the nature of the movementpattern underlying the goal outcome,is called "knowledge of performance"(KP) (see article by Gentile32 for fur-ther discussion). Using the same clini-cal example, KP might be given byindicating the degree to which thepatient leaned his or her trunk andhead forward prior to rising from thechair. In contrast to KR, which inmany everyday behaviors tends to beredundant with intrinsic feedback, KPrepresents the kind of extrinsic feed-back most often given to performers(and our patients) in natural (or clini-cal) settings. Knowledge of results,however, has been the focus of a ma-jority of the experimental and theoret-ical research on information feedbackand learning.33 This preference for KRin empirical work has primarily beendue to the ease with which it can beobtained, manipulated, and quantifiedin the experimental laboratory. Al-though more research using KP varia-bles is needed, the existing studiesindicate that KP variables behave simi-larly to KR variables with regard tomotor learning.The Knowledge-of-ResultsResearch ParadigmResearchers examining the relation-ship of feedback to motor skill learn-ing must control the multiple sourcesof feedback that are available in natu-ral settings. Frequently, an experimen-tal environment is created in whichthe usefulness of intrinsic feedbackpenaining to the movement outcomeis minimized. Feedback is then sys-tematically reintroduced (usually inthe form of KR), and its effects on thelearning process are examined. Suchan experimental design may closelymimic the conditions of a patient withsensory deficits who is unable to ef-fectively use intrinsic feedback for

motor control and thus must rely the extrinsic feedback provided bythe therapist.This research paradigm is based othe premise that KR functions withrespect to these artificial laboratortasks in the same way that intrinsicfeedback functions in real-life movment situations. Processes facilitatby the use of extrinsic feedback inlaboratory, such as error correctioor the development of an internalreference of correctness, thereforeare thought to be similar to thoseprocesses facilitated by the use of trinsic feedback sources in naturalsettings in which KR is unavailableredundant.The KR research paradigm has notescaped criticism by those who qution the generalizability of researchfindings, from the usually one-dimensional motor tasks used in thparadigm to the multidimensionalcoordinated actions found outsidelab0ratory.23,3*~35 urrently, little isknown about the complex interac-tions of the multiple sources of feeback available through more naturactions. The principles gleaned frothe KR research paradigm may offebest only minimal insight into thefunctioning of intrinsic feedback inmultidimensional movements. Theprinciples may be quite different ireal-life situations. The evidence isquite extensive, however, that KR ian important determinant of behavioral change in these laboratory setings.36~37Thus, an understanding othe principles governing how infomation feedback affects motor behior has practical implications or atleast could provide guidelines22 foteachers, therapists, and performerhas provided a critical cornerstonetheory penaining to the learning pcess itself.18J9Learning Versus PerfomlanceResearch in motor learning requiran operational definition of "learning." Scientists have typically founduseful to define learning as a set ointernal processes associated withpractice or experience leading to a

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relatively permanent change in thecapability for responding. 3 Theseprocesses are thought to be complexcentral nervous system phenomenawhereby sensory and motor informa-tion is organized and integrated.3-Although some researchers, usingclassical conditioning paradigrns,41have begun to isolate the neural sub-strates associated with learned behav-iors in animals, behavioral research-ers investigating humans must usuallyinfer from a change in behavior thatlearning has occurred. Not all behav-ioral changes, however, reflect learn-ing. This caveat becomes an importantconsideration for designing experi-ments in the laboratory as well as as-sessing the effects of a treatment inter-vention in the clinic. Of the numer-ous variables that influence behavioralchange, some (eg, fatigue, drugs) arethought to effect only temporarychanges, others (eg, practice) are con-sidered to change behavior in morepermanent ways, and still others (eg,KR) are thought to effect both temporary and relatively permanentchanges. The motor learning re-searcher, as well as the clinician, isusually interested in those variablesthought to effect relatively permanentchanges in behavior. How arechanges in behavior attributable totempol-ary factors distinguished fromchanges attributable to more perma-nent effects?One way motor learning researchersexperimentally distinguish the rela-tively permanent effects of variouspractice variables from the temporaryeffects is by using a transfer design.42This design typically involves two dis-tinct phases: (1) an acquisition, orpractice, phase in which differentgroups receive treatments represent-ing various levels of the independentvariable (eg, different schedules ofextrinsic feedback) and (2) a tramferphase in which all groups are trans-ferred to a common level of the inde-pendent variable (eg, no feedback).The transfer phase is sufficiently sepa-rate in time from the acquisitionphase such that the temporary effectsfrom the independent variable havehad adequate time to dissipate. Thus,performance in the transfer phase can

be said to reflect the learning p r oduced by the independent variableduring the acquisition phase.Knowledge of Results andMotor LearningIn general, KR is considered a prac-tice variable that is capable of effect-ing both temporary and relatively per-manent (ie, learning) changes inperformance. Given this potentiallyambiguous state, proper experimentaltechniques such as transfer designsmust be used to determine which KRvariations are important for learning(see article by Salmoni et all for fur-ther discussion).The motor learning literature andclinical practice protocols are sur-prisingly consistent in showing that,during the practice phase in mosttasks, nearly any variation that in-creases the availability (eg, immedi-acy, precision, frequency, number ofchannels) of information feedbackbenefits performance and increasesthe rate of improvement over tri-als.43,44 ecause performance bene-fits from such conditions, it is easyto assume that these conditions alsobenefit learning and retention. Re-cent research, however, has re-vealed that certain variations of KRthat provide information feedbackless ofen during practice prove tobe more beneficial for long-termlearning and retention than practiceconditions with feedback providedmore often. These feedback varia-tions that appear to enhance learn-ing pertain to the scheduling of KRduring practice and include (1) KRrelative frequency, which is the pro-portion of trials receiving KR37;(2) bandwidth KR, which providesKR after trials for which perfor-mance is outside a given error tol-erance range45; and (3) KR delay,which provides KR following sometemporal delay after completion of aresp0nse.~6 hese potentially impor-tant KR variations have been exam-ined exclusively with healthy sub-jects learning novel laboratory tasks.Results from each KR variation willbe reviewed first, followed by ageneral discussion with comments

regarding clinical implications forphysical therapy.Relative frequency of knowledgeof results. Operationally, the relative

frequency of KR is the proportion ofpractice trials for which KR is p n ,vided, whereas absolute frequencyrefers to the total number of trials forwhich KR is provided in a practicesession. These KR frequency variablesare relevant to structuring the learn-ing environment and thus have re-ceived considerable attention.33 Oneof the earliest and most influentialstudies of KR relative frequency, con-ducted over 30 years ago by Bilodeauand Bilodeau,47 involved a simplelever-pulling task. Four differentrelative-frequency practice conditionswere produced by holding the num-ber of KR trials constant (ie, absolutefrequency was 10) and varying thenumber of interspersed noKR prac-tice trials. In their experiment, the KRrelative frequencies were lo%, 25%,33%, and 100%. Because the numberof practice trials was allowed to varywith relative frequency, the 100%group practiced the task for 10 trialsand received KR after each trial. The33% group practiced the task for 30trials and received KR after everythird trial. The 25% group practicedthe task for 40 trials and received KRafter every fourth trial. Finally, the10% group practiced the task for 100trials and received KR after every 10thtrial. Blindfolded subjects pulled avertically extended hand lever to agoal position. Knowledge of resultsabout the direction and amount ofposition error was presented in ac-cord with the particular relative-frequency schedule.Comparison of the four groups oneach of the trials immediately follow-ing each KR trial (ie, KR + one trial)revealed no differences attributable torelative frequency. This finding sup-ported an assumption that the noKRtrials interspersed among the KR pre-sentations were not particularly use-ful. This assumption was later shownto be invalid. For the 10% group, asexpected, performance deterioratedon the sets of nine intervening no-KRtrials. Bilodeau and Bilodeau con-

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cluded that "learning is related to theabsolute frequency, and not the rela-tive frequency of KR."47(p382) Becausea transfer or retention test was notconducted, the learning-performancedistinction, long known to learningpsychologists,48 could not be evalu-ated. Bilcdeau and Bilodeau's experi-ment, therefore, provides evidencewith regard to motor performance,but not with regard to motorlearning.Iater experiments by Ho and Shea49and Johnson and colleagues (RWJohnson,GGWicks,D Ben-Sira; un-published data; 1981) extended thework of Bilodeau and Bilodeau47 byusing no-KR retention tests and simi-larly simple motor tasks. Results fromthese studies suggested that KR relativefrequencywas an important variablefor learning. Apparently, conditionswith less frequent KR, hough detri-mental to immediate performance dur-ing practice, were beneficial to learn-ing as measured on a neKR retentiontest. These experiments, and Bilodeauand Bilodeau's47 study, confounded thetotal number of trials and KR relativefrequency, making the results difficultto interpret. The apparent beneficla1effects from practice in low relative-frequency conditions could haveamen simply from the amount ofpractice and not the relative KRfrequency.Recently, an attempt was made to op-timize the beneficial learning effectsattributed to practice in reduced KRrelative-frequency conditions bymanipulating the schedule of KR andno-KR trials within the practice ses-sion.37 Two groups of subjects prac-ticed a complex spatial-temporalmovement pattern over a 2-day pe-riod under either high (100%) ormoderate (50%) relative-frequency KRconditions. In this experiment, thenumber of trials (196 per day) washeld constant across groups, thus al-lowing relative and absolute fre-quency to covary. A "faded" KR sched-ule was used in the 50% condition,such that on each day the proportionof KR trials was relatively high early inpractice (100%) but was graduallyreduced toward the end of practice

100%50%

0

8 11L

9 L rn7::\%-V4 6 8 Hb10 12 14 16 Imm DelAcquisition RetentionFigure 1 . Average error score for the 50%-KR and 1W/o-KR relative-frequencygroups during the 2-day acquisition phase (blocks 1-16) and the immediate (Imm) aI-day delayed (Del) no-KR retention phases. Each block is the average of 12 trials.(Adapted from Winstein and Schmidt.37)(25%). Following 2 days of practice, a5-minute (immediate) and a l d a y(delayed) no-KR retention test wasadministered to each group.Figure 1 shows the average errorscores for the two relative-frequencygroups across trial blocks during the2-day acquisition phase and the im-mediate and delayed retention phases.There were no overall group differ-ences during the acquisition phase.On the immediate neKR retentiontest, the 50%-KR group performedwith a slightly lower error score (8.5versus 9.2) than the 100% group, and,on the delayed no-KR retention test,the 50%-KR group performed 35%better (10.0 versus 12.1) than the100%-KR group. As illustrated in Fig-ure 1,performance for both groupsdeteriorated (ie, error scores in-creased) between the end of acquisi-tion and retention, but the 100%-KRgroup showed greater deteriorationthan did the 50%-KR group.These findings run counter to theconventional viewpoint that less fre-quent KR should degrade learn-ing.l8,19,5O Instead, a condition withless frequent KR was shown to en-hance learning, at least as measuredon a neKR retention test. From apractical smdpoint , conditions that

provide KR more frequently may bappealing because of the temporareffects on performance. These effehowever, may not be beneficial tolearning in the form of retention pformance when compared with cotions with less frequent KR. Not suprisingly, when performance wasexamined on trials for which KR wnot provided, the subjects in the50%-KR condition demonstratedlarger error scores than did subjecin the 100%-KR condttion on corrsponding acquisition trials.37 This tionship, however, was reversed wperformance scores for the groupwere examined in the delayed neKretention test.These results were replicated in asecond experiment37 in which a dlayed KR retention test was used. this experiment, the same KR scheule was used as in the previous experiment during a 2-day practice priod. Instead of a no-KR retentionhowever, a 12-trial, 1-day delay retion test was administered in whicKR was provided after each trial. Sprisingly, the 50%-KR group per-formed significantly better than th100%-KR group even o n this 100%retention test. The faded 50% relafrequency KR schedule seemed tofacilitate the development of a cap

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bility for responding that appearedimmune to the particular superficialcharacteristics of the practice and re-tention conditions. Although a superfi-cial similarity between low relative-frequency KR practice and retentiontest conditions cannot account forthese findings, it may be that a simi-larity in processing operations, as sug-gested by Lee'ssl concept of transferappropriateness, could account forthese results.Bandwidth knowledge of results.In bandwidth KR , feedback is pro-vided only if the performance re-sponse is outside a given range (ie,window of acceptable performance).This procedure is quite different fromthe KR relative-frequency variationthus far considered, in that the ab-sence of KR actually informs the sub-ject that the previous response wasacceptable. Bandwidth KR, therefore,provides two kinds of feedback:(1) feedback that is motivating fortrials that fall inside the bandwidth(eg, "Good, d o that again.") and(2) feedback that is informative withrespect to er rors for trials that falloutside the bandwidth.Sherwood45 investigated the effects ofbandwidth KR with a ballistic timingtask in which a lever was to bemoved through a target amplitude inexactly 200 milliseconds. He used 5%and 10% bandwidth KR conditionsand one control condition for whichKR was provided on every trial,termed the 0% bandwidth. In the 5%bandwidth KR condition, subjects re-ceived movement-time KR if their ab-solute error was greater than 10 milli-seconds. Similarly, the 10% groupreceived KR if movement time erro rwas greater than 20 milliseconds.Sherwood's results showed no differ-ences between groups during acquisi-tion and no differences in retention interms of performance accuracy. The10% bandwidth KR group, however,performed more consistently fromtrial to trial and with higher overallaccuracy on the retention test thaneither the 5% bandwidth KR or con-trol groups.

These retention-test results with band-width KR are consistent with those forKR relative frequency. Overall accu-racy was highest for those subjectswho practiced in conditions with lessfrequent KR trials. On the average, inShenvood's45 study, the 5% band-width KR group received KR at anaverage frequency of 54% of the tri-als, whereas the 10% bandwidth KRgroup received KR at an average fre-quency of 31%. Because larger band-width KR conditions result in reducedKR relative frequencies comparedwith smaller bandwidth conditions, itwas unclear how much of the benefi-cial effects from larger bandwidthswere du e simply to the reduced rela-tive frequency.Lee and Carnahan52 attempted to un-ravel the contribution of KR relativefrequency from the bandwidth KRvariation by using an experimentalprocedure known as "yoking." Theycompared the performance of sub-jects in four KR conditions using atiming task with a 500-millisecondgoal. Two of the groups had similarconditions to those used in Sher-wood's study,45 namely 5% and 10%bandwidth KR groups that receivedverbal KR about their timing errorsaccording to the prescribed band-widths. The other two groups hadconditions, designated the yoked-5%and yoked-10% conditions, that werecreated by pairing each of the band-width subjects with a yoked counter-part who received the same KR sched-ule. Hence, subjects in the yokedconditions received KR about theirown performance on precisely thesame trials as the bandwidth KR sub-jects. Because the paired subject's KRschedule was being used, however,the KR was not customized to theyoked subject's performance, nor wasthe absence of KR indicative of"g oo d performance as it was in thebandwidth KR conditions.The results of Lee and Camahan's52experiment indicated that the benefi-cial effects of a bandwidth KR condi-tion on learning were not simply dueto a relative-frequency KR effect. Dur-ing acquisition, the bandwidth KRcondition seemed to enhance accu-

racy and stability over that achieved inthe yoked relative-frequency KR con-ditions. During retention, althoughthere were n o significant differencesbetween groups with respect to accu-racy, the subjects in the bandwidth KRconditions were less variable (within-subject variable error) in their perfor-mance than those in the yokedrelative-frequency KR conditions. Thebeneficial learning effects of the band-width KR variation over a purerelative-frequency KR condition thusappear to b e most pronounced withrespect to movement consistency. Be-cause skilled performances are char-acterized as being both accurate andstable, feedback variations that en-hance performance consistency areequally as important as those that pro-mote accuracy.

Knowledge of results delay.Another KR variation known as KRdelay refers to the timing of KR. TheKR delay interval is the amount oftime between the completion of theaction and the presentation of theKR.13 Theoretically, this interval hasbeen thought to contribute to forget-ting of the movement memory byallowing decay of the memory trace.Thus, lengthening the interval be-tween movement response and KRwas thought to be detrimental tolearning. According to this view,shortening the KR delay interval asmuch as possible should benefitlearning. It is interesting that high-technology, computer-assisted feed-back devices recently available forvarious kinds of movement retrainingare designed to provide instantaneousfeedback to the performer (ie, the KRdelay has been essentially eliminated).The KR review by Salmoni et al,'however, indicated that, in general,increasing the KR delay interval doesnot appear to degrade learning and,in some cases, might even enhancelearning. Conversely, in this same re-view, the authors suggested that therewere some hints from the literaturethat shortened KR delays might de-grade learning.Swinnen and co ll eag ~es *~ecentlycompared skill acquisition for a groupof subjects receiving 100% KR after a

Physical Therapy I Volume 71, Number 2 /February 1991by guest on December 14, 2011http://ptjournal.apta.org/Downloaded from
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short delay with an other gr ou p re-ceiving 100% KR instantaneously. Inthe first exp erim ent, a timing taskwith two movemen t reversals wasused. Three KR conditions were used:(1) an instantaneous KR condition inwhich the subject was presented withKR immediately after completion ofthe movement, (2) a delayed KR con-dition in which the subject had an8-second unfilled interval between thecompletion of the movement and thepresentation of KR, an d (3) an estima-tion condition in which the subjecthad an 8-second interval between thecompletion of the movement and thepresentation of the KR during whichhe o r she was required to orally esti-mate his o r her m ovement time.The results of this first exper ime nt,illustrated in Figure 2, show ed n oprono unced differences in perfor-mance between the three groups dur-ing the acquisition phase. On the 10-minu te and 2-day retention tests,however, the instantaneous KR groupshowed marked deterioration in per-formance relative to the other twogroups. On the delayed (2-day) reten-tion test, the estimation gro up p er-form ed significantly better than th einstantaneous KR group , whereas thedelayed KR group performed at alevel between the other two grou ps.These results suggested that instanta-neous KK may have degraded learn-ing by blocking o r interfering withimportant information-processing op-erations associated with the develo p-ment of error-detection capabilities.46The estimation gr ou p had significantlyless error than the instantaneous KRgro up o n the delayed retention test,suggesting that evaluation of resp onseerrors during the KR interval wasbeneficial for learning.In a second exp eriment, a complexcoincident-timing task and two KRdelay conditions were used. The in-stantaneous KR gro up received 100%KR 210 milliseconds after responsecompletion, and the delayed KRgro up received 100% KR 3.2 secondsafter response completion. By the endof the sec on d day of practice, the in-stantaneous KR group demonstrated asignificantly wors e p erformance than

160.. 9 Estlmstlon4- Instantaneous KR4- Delayed KR2 120.-8V)

L

' 80.bb40"

0 q : : : : : : : : t

@d- ----C--I2 4 6 8 10 12 14 16 1810 min 2 d

Acquisition RetentionFlgure 2. Average ewor score for the three kX delay groups during the acquisiphase (blocks 1-18) and the 10-minute and 2-day no-kX retention phases. Each blocthe average of3ve trials. (Adaptedfi-om Swinnen et al.46)the delayed KR group. This same rela-tionship persisted through severalretention tests (immediate and de-layed), demonstrating the detrimentaleffects of instantaneou s KR o nlearning.Swinnen and associates suggest that

the use of frequent or instantaneousfeedback can discourage the process-ing of other kinds of information, suchas intrinsic response-produced feed-back that would lead to the learning ofthe capability to detect errors in futureperforrnances.46@22)

From a p ractical standpo int, this re-search suggests that an adequate KRdelay interval b e provided to allowfor the processing of relevant re-sponse and task information. Thismetho d of providing KR is in directcontrast to that of som e practitioners,who advocate the provision of feed-back imm ediately o r continuously.53.54It may be that early in the reacquisi-tion phase, the patient needs m oreimmediate KR to "get the idea of thetask," but care should b e taken to pre-vent overreliance on the extrinsicfeedback at the expense of the devel-opment of an internal reference of

correctness necessary for long-termretention and learnin g. Persons wineurological deficits may requ irelonger, or perhaps even shorter, Kintervals than healthy age-matchedcontrols. In addition, relevant to dsigning computer-assisted feedbacdevices, it is apparent from this wothat, although th e provision of instaneous feedback may be beneficiafor performance during practice, ican be detrimental for learning anretention.Theoretical and PracticalimplicationsIn the relative-frequency, bandwidan d KR delay variations previouslydiscussed and in the summ ary KRvariation not addresse d in this arti(see articles by Schm idt and col-leagues36,55), tho se con dition s inwhich KR was provided less fre-quently o r less immediately w eremo re beneficial for m otor learninthan conditions in which KR was pvided m ore frequently or without lay. Some researchers36~7~46~ 51avesugge sted that these beneficial KRpractice conditions invoke certaininformation-processing operations

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that are beneficial for learning. Thefollowing discussion briefly highlightssome of the current hypotheses re-garding what these beneficial pro-cesses might be. For a more detaileddiscussion with associated arguments,the original sources should beconsulted.

One view, termed the "guidance hy-pothesis,"36,56holds that when KR isprovided frequently, the subject beginsto rely on its guiding properties. TheKR is said to act like a crutch that isnot needed to the degree to which itis used. This overdependence on KRmay actually prevent the processing ofimportant task-related information (eg,response-produced feedback) and thusblock the development of error-detection capabilities needed at thetime of retention and transfer.Another view, termed the "consisten-cy hypothesis," is supported by anumber of studies. This notion sug-gests that frequent KR induces fre-quent response modifications called"maladaptive short-term correc-t i o n ~ . " ~ ~hese frequent responsemodifications make performance in-consistent from trial to tria1.57-59 Thisinduced response variability interfereswith the establishment of a stable ac-tion plan necessary for later responseproduction.Finally, it has been suggested that aschedule with intermittent KR allowsfor a more obvious contrast betweenperformance driven by KR and perfor-mance that is independent of KR (ie,during no-KR trials). It is evident thatperformance errors are greater dur-ing no-KR trials than during KR tri-a1s.37852.60,61he nature and awarenessof errors may only become apparentto the subject following the next KRtrial. In contrast to a schedule withfrequent KR, an intermittent KRschedule provides an opportunity forthe subject to obtain informationabout performance errors (eg, driftfrom the target pattern) that occurwhen KR is not directly influencingthe response. This process of compar-ison may be beneficial for learning inthat it gives the subject informationabout errors during performance that

is not influenced by any extrinsicfeedback. Although performance fortrials not preceded by KR appears byimmediate standards to be relativelypoor (ie, less accurate, although itmay be more consistent, especiallywith bandwidth KR), the information-processing operations suggested tooccur during this period seem to bebeneficial for learning.The KR research presented suggests aneed to reexamine treatment ap-proaches that advocate performanceaccuracy, strong guidance (eithermanual, tactual, or verbal), frequentand continuous feedback, and avoid-ance of errors o r "abnormal" move-ments. Considering the learning-performance distinction with regardto these treatment practices may wellaccount for the often-cited minimal"carry-over" and limited retention ofnewly acquired motor skills. Perhapsa new set of treatment guidelinesbased o n the KR literature wouldprove usefu1.62263Highly skilled and experienced thera-pists appear to intuitively use tech-niques analogous to the faded, inter-mittent, bandwidth, and delayed KRconditions, although their rationalemay not be well developed or under-stood from the perspective of motorlearning principles. In any attempt tobridge the gap between basic re-search and practice, it is important tounderstand that the principlesgleaned through laboratory experi-mentation are best used as guidelinesfor practice, as opposed to specificdo's and don't's.22 Direct applicationof the KR laboratory research to clini-cal intervention should be cautiouslyused until the proper clinical studieshave been conducted. Applied re-search from which more specific rec-ommendations can be made in thepractical domain is needed.In terms of clinical procedures,these findings imply that the once-advocated use of feedback in a man-ner consistent with the adage "moreis better" no longer seems appropri-ate. The view advocated by motor-learning researchers and cliniciansregarding the beneficial learning ef-

fects of feedback variations that tendto increase the amount or frequencyof KR should be challenged.64It seems clear from these initial find-ings with healthy subjects that certaininformation-processing operationsfacilitated by conditions with less in-formation feedback are better forlearning than those with more fre-quent or more immediate feedback.Although this finding might seemcounterintuitive, it appears that forc-ing the learner to actively developproblem-solving strategies indepen-dently of the guidance provided byfeedback (and the therapist) is actu-ally beneficial for motor learning.65>66An understanding of the processesunderlying these beneficial effects willbe important for new developmentsin theory, practice, and the training ofphysical therapists (as learners of newmotor skills). For the growing knowl-edge base of physical therapy, an un-derstanding of the principles underly-ing the use and misuse of augmentedinformation feedback could fosternew insights, challenge present prac-tices, lead to hypothesis testing, andprovide for the development of the-ory as a basis for new or revisedtherapeutic and educationalpracti~es.6~-6*,67Motor Learning,Physlcal Therapy, andFuture DlrectlonsAlthough it can be argued that theknowledge base of motor learning-particularly as related to the use offeedback (KR and KP)-is highly rele-vant to physical therapy, few entry-level education programs have incor-porated this knowledge base in theircurricula (although there is evidencethat this situation is changing). Educa-tional curricula have developed, inconcert with the needs generated byprofessional practices rather thandiscipline-based knowledge. Early inour professional growth, we drewheavily from the medical model, andthe foundations for our practices gen-erally were based on what werethought to be fundamental clinicalsciences. As we develop a broader

Physical Thera] y /Volume 71, Number 2 /February 1991by guest on December 14, 2011http://ptjournal.apta.org/Downloaded from
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~e rs~ec t iveor both entni-level and Calif: Journal Publisher AEiliates; 1976;4:195-. .postgraduate education, our knowl- 228.13 Schmidt RA. Motor Control an d Learning:edge base must reflect that A Behavioral Emphasis. Champai~n,ll: Human-ment. As programs in movement sci- Kinetics ~u bli shg rs nc; 1988.ence begin to re ~r esen the norm in 14 Maaill RA. Motor Learninp Co nce ~ts ndL.physical therapy,'our entry-level cur- ~ppl ica2on. nd ed . ~ ub uq ucowa: k'm CBrown Group; 1989.ricula will also evolve in a similar 15 Christina RW. Motor learning: future linesmanner.Acknowledgments

of research. In: Safrit MJ, Eckert k ~ ,ds TheCutting Edge in Pb)~sical ducation and Ewer-cise Science Research. Champaign, Ill: HumanKinetics Publishers Inc; 1987:2641.16 Light ICE. Information processing for mo-Critical and insightful comments on tor performance in aging adults. Phys Ther.an earlier version of this article were 1990;70:820426.

provided by my colleagues Beth 17 Pew RW. Toward a process-oriented the-Fisher, Helen Hislop, Rebecca Lewth- ory of human skilled performance. ournal ofMotor Behavior 1970;2:8-24.waite, Joan Walker, Patricia Pohl, and 18 AdamsJA, A closed-loop theory of motorMary Ruth Velicki. I gratefully ac- learning.Journal of Motor Behavior.knowledge their contributions.

References1 Salmoni AW, Schmidt RA, Walter CB.Knowledge of results and motor learning: areview and critical reappraisal. Psychol Bull.1984;95:355-386.2 McCullagh P, Weiss MR, Ross D. Modelingconsiderations in motor skill acquisition andperformance: an integrated approach. In: Pan-dolf KB, ed. Exercise and Sport Sciences Re-t~iews.Baltimore, Md: Williams & Wilkins;1979:475-513.3 Schmid~: A, Young DE. Transfer of move-ment control in motor skill learning. In: Corm-ier SM, Hagman JD, eds. Transfer of Learning.Orlando, Fla. Academic Press Inc; 1987:47-79.4 Feltz Dl., landers DM. The effects of mentalpractice on motor skill learning and perfor-mance: a nieta-analysis. Sport PJychol.1983;5:25-57.5 Locke FA, haw KN , Saari LM, latham GP.Goal setting and task performance: 1969-1980.Psychol Bull. 1981;90:125-152.6 Wrightman DC, Lintern G. Pan-task trainingfor tracking and manual control. IIum Factors.1985;27:267-283.7 Shapiro DC, Schmidt RA. The schema the-ory: recent evidence and developmental impli-cations. In: Kelso JAS, Clark JE, e d ~ .he Deuel-opment of Movement Control andCoordination. New York, NY: John Wiley &Sons Inc, 1982:113-150.8 Magill RA, Hall KG. A review of the contex-tual interference eEect in motor skill acquisi-tion. Human Mouement Science. In press.9 Gill DL. Psychological Dynamics of Sport.Champaign, Ill: Human Kinetics Publishers Inc;19%.10 Rejeski WJ, Brawley LR . Defining theboundaries of spon psychology. The Sport Psy-chologist. 1988;2:231-242.11 Bilodeau FA , Bilodeau 1M. Motor-skillslearning. Iri: Farmswonh R , McNemar 0,McNemar (2, ds. Annual Rerlieru of Psl.chol-ogy. Palo Alto, Calif: Annual Reviews Inc;1961;12:2455-280.12 Newel1 KM. Knowledge of results and mo-tor learning. In: Keogh J, Hutton RS, eds. Erer-cise a n d Sport S ciences Ret:ieups Santa Barbara,

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