Outflow and inflow in movement duplication

BILL JONESUniversity of Queensland, St. Lucia, Queensland, Australia 4067

Thirty Ss were assigned randomly to one of three conditions of blindfoldedmovement duplication: (1) constrained active movement (the E determined theend point of the S's movement), (2) unconstrained active movement, and(3) passive movement. Ss' absolute accuracy of duplication of the threeconditions was compared. Significant differences were observed between thethree conditions, though there was no significant difference between Conditions1 and 3. The results are discuased in terms of "outflow" and "inflow" models ofkinesthesis, and it is argued that some support is given to the outflow model.

Condition 1 Condition 2 Condition 3

2.03 1.78 0.88 0.85 2.15 2.13

SDMSDMSDM

tried to duplicate the passivemovement, as in Conditions 1 and 2.

Under all procedures, Sa wereblindfolded so that they could notview their movements. UnderConditions 1 and 3, there were 50trials using distances of 10, 15, 20, 25,and 30 cm, 10 times over in a randomorder. There were similarly 50 trialsper S under Procedure 2. Sa' absoluteerror on each trial was recorded inmillimeters.

RESULTSContrary to Posner (1967), no

evidence of a correlation betweenextent of standard and accuracy ofreproduction could be found, and datahave been combined irrespective of thelength of the standard for all threeconditions. The difference betweenthis finding and that of Posner may bedue to the fact that I studiedmovements to the side of the body,whereas Posner studie;movements infront of the body. Mean absolute errorscores and standard deviations for thethree conditions are given in Table 1.Absolute error scores here are, in fact,equivalent to underestimation scores,since no S in any condition showedany tendency to overestimate, unlikethe studies of Paillard and Brouchon(1968), who found some tendency tooverestimate in passive conditions.

Since it cannot be assumed that therange of active movements had anormal distribution, the data wereanalyzed by means of thenonparametric Kruskal-Wallis one-wayanalysis of variance (Siegel, 1956),which indicated significant differencesbetween conditions (H = 20.89, df = 2,p < .001). When Conditions 1 and 3were compared by means of a t test,there was no significant difference(t =0.11, df = 18). In other words,constrained active movements areapparently indistinguishable frompassive movements in the presentexperiment.

Though unconstrained activemovement is more accurate than eitherof the other two conditions, this mayhave been because Ss in this conditionused a smaller and less variable rangeof movements. However, every S inCondition 2 selected a range ofmovements greater than 20 em, therange of the standards in the other twoconditions. The smallest range chosen

Table 1Mean Absolute Error and Standard Devia­

tion in Centimeters for the ThreeMatchinl Conditions

METHODSubjects

Thirty university undergraduatesserved as Ss. Ten were assignedrandomly to each of threeexperimental procedures.

ApparatusA thimble was mounted on a rail

and could be slid along it by the S orthe E. A pointer attached to thethimble moved along a scale below theslide and enabled the E to read off thedistance which the slide had moved.

ProcedureCondition 1: Constrained active

movement. The S, with his indexfinger in the thimble, moved it alongthe rail as quickly as possible until hecame to a stop set by the E. He thenmoved back to the starting point andtried to reproduce as accurately aspossible his previous movement, the Emeanwhile having removed the stop.

Condition 2: Unconstrained activemovement. The S placed his indexfinger in the thimble and moved italong the rail as quickly as possible towhatever position he preferred. Hethen moved back to the beginning andattempted to duplicate the firstmovement.

Condition 3: Passive movement.The S placed his index finger in thethimble and the E moved the thimbleas quickly as possible to apredetermined position, then moved itback to the starting point. The S then

the S himself who moves and passivein that the S can make no decisioneither in advance or during the courseof the movement about where he willfinish. The hypothesis was thatunconstrained active movements areduplicated with greater accuracy thanboth passive and constrained activemovements. If constrained activemovements were duplicated only withthe accuracy of passive movements, weshould have evidence for the role ofcentral monitoring of efference signalsin that absence of "preset" controlleads to deterioration in duplication ofactive movement.

Despite emphasis by many theorists(e.g., Bahrick, 1957; Gibbs, 1954,1965; Annett, 1971) on the role ofproprioception in human performance,there have been f.,w studies of Ss'ability to reproduce movementswithout visual guidance. Howard andTempleton (1966) could list only twostudies dealing with the duplication ofextent of movement without vision:Woodv. orth (1899) and Hollingworth(1909).

In general, theorists have taken forgranted the role of proprioceptivefeedback signals in skilled performanceand have ignored the alternativetheory that in the absence of visual (orother exteroceptive) guidance, thecentral nervous system (CNS) mayhave knowledge of active movementby monitoring its own efferent signals(this latter theory will be referred tohere as "the efferent outflow theory,"outflow for short, and is contrastedwith the feedback or "proprioceptiveinflow theory," inflow for short).Since inflow theories need to assumecentral monitoring of efferent signalsto give a "template" against whichproprioceptive signals may becompared (e.g., von Holst, 1954) andsince studies with spinallydeafferented animals (reviewed byTaub & Berman, 1968) have shownthat proprioceptive signals are not anecessary condition for movementlearning, the outflow theory is, in fact,the more parsimonious account.

The aim of the present experimentwas to provide some evidence of theimportance of outflow VB inflow in theduplication of movements. For theperception of movement to be servedby outflow, the S would need to knowthe goal of his movement in advance.The ability of Ss to duplicateunconstrained voluntary armmovements and passive movements ofthe same limb was compared to theirability to duplicate their armmovements when they had noknowledge at the beginning of themovement of its end point. This"constrained movement" sharescharacteristics of both active andpassive movement-active in that it is

Perception & Psychophysics, 1972, Vol. 12 (IB) Copyright 1972, Psychonomic Society. Austin, Texas 95

Table 2Relationship Between Accuracy andStandard Settings in Centimeters for Ss

in Condition 2

MeanSettings

S Accuracy M SO

1 94 25.84 17.522 96 33.12 7.093 84 38.43 14.874 86 37.91 11.745 87 26.28 5.046 98 30.18 11.337 89 34.37 10.308 80 32.69 16.659 85 38.43 9.24

10 86 40.27 8.30

was 35 em (20-55 cm) and the overallrange was 62.5 (5-67.5 cm) ascompared with 20 em for the othertwo conditions. Table 2 shows meansand standard deviations for standardsettings against mean accuracy for allSs in Condition 2. There is no clearrelationship between standard settingsand accuracy, and it is obvious thatevery S made mean standard settingsin excess of the mean of 20 em in theother two conditions; only two Ss hadstandard settings which were lessvariable than settings in Conditions 1and 3, where the standard deviationwas 7.07.

DISCUSSIONThough Ss were instructed to move

as quickly as possible, there may havebeen differences between groups inpatterns of acceleration anddeceleration. Characteristically, Ssdecelerate near target position(Annett, Golby, & Kay, 1958).Without a known target position, Ss'movements in Condition 1 are unlikelyto have shown a decelerating phase.Thus there is a possibility, which Iwould like to leave open, that possibledifferences between conditions in thisrespect may have influenced thepresent results.

At least two hypotheses couldaccount for the greater accuracy ofmovement duplication of Condition 2.Duplication of movement here couldbe based on outflow plus inflow withproprioceptive signals serving to stampin the centrally monitored efferentcopy. Alternatively, proprioceptivesignals might be no more thanregistration of muscular effort(Merton, 1964) without informationas to direction or extent of movement.Duplication of movement would

consequently be mediated by outflowalone.

Since the outflow plus inflowaccount is frequently assumed, it maybe in order to speculate that centralmonitoring of efference can by itselfmediate knowledge of activemovement. There is considerableevidence that, following passive stretchof muscle, only the joint receptors cancalibrate accurately changes indirection and extent of movement(Boyd & Roberts, 1953; Skoglund,1956; Rose & Mountcastle, 1959;Burgess & Clark, 1969).Anesthetization of the joint capsuleabolishes the perception of passivemovement but leaves the ability toperceive and duplicate voluntarymovement unimpaired (Browne, Lee,& Ring, 1954). Consequently, weknow that joint receptors rather thanmuscle spindles are implicated inpassive movement, but joint receptorfiring is not necessary in voluntarymovement. Since the muscle spindledoes not signal changes in direction orextent of movement during passivestretch (Rose & Mountcastle,1959), the parsimoniousassumption is that the proprioceptorsare not concerned in supplyingfeedback signals during active stretchand that, instead, monitoring of itsown efference provides the CNS withsufficient data for control ofmovement.

To save the inflow theory, wewould need to assume, as do Paillardand Brouchon (1968), that the musclespindle is tied in with active movement(they do not explain why the patternof firing by the spindle should bedifferent for voluntary and passivemovement). Since there is no reason tothink that the behavior of the musclespindle differs in the constrained andunconstrained conditions, the presentparadigm provides a crucial testbetween the Paillard and Brouchonhypothesis and the outflow theory. Ifthe joint capsule is blocked byanesthetic, and constrained activemovement still differs significantlyfrom unconstrained and passivemovements as here, the Paillard andBrouchon hypothesis would berefuted.

REFERENCESANNETT, J. Acquisition of skill. British

Medical Bulletin, 1971,27,266-271.

ANNETT. J., GOLBY, C. W., & KAY, H.The measurements of elements in anassembly task-the information output ofthe human motor system. QuarterlyJournal of Experimental Psychology,1958, 10, 1-11.

BAHRICK, H. An analysis of the stimulusvariables influencing the proprioceptivecontrol of movements. PsychologicalReview, 1957, 64, 324-328.

BOYD, I. A., & ROBERTS, T. D. M.Proprioceptive discharge endings in theknee joint of the cat. Journal ofPhysiology, 1953, 122, 38-59.

BRINDLEY, G. S., & MERTON, P. A. Theabsence of position sense in the humaneye. Journal of Physiology, 1960, 153,127.

BROWNE, K., LEE, J., & RING, P. A. Thesensation of passive movement at themetatarso-phalangeal joint of the greattoe in man. Journal of Physiology, 1964,126,448-458.

BURGESS, P. R., & CLARK, F. J.Characteristics of knee joint receptors inthe cat. Journal of Physiology, 1969,203. 317-335.

GIBBS, C. B. The continuous regulation ofskilled response by kinaesthetic feedback.British Journal of Psychology, 1954, 45,24-39.

GIBBS, C. B. Probability learning instep-input tracking. British Journal ofPsychology, 1965, 56, 233-242.

HOLLINGWORTH, H. L. The inaccuracy ofmovement. Archives of Psychology, NewYork, 1909, 2, 1-87.

HOLST, E. von. Relations between thecentral nervous system and peripheralorgans. British Journal of AnimalBehaviour, 1954, 3,89-9•.

HOWARD, I. P., 8< TEMPLETON, W. B.Human spatial orientation. New York:Wiley, 1966.

MERTON, P. A. Human position sense andsense of effort. Symposia of the Societyfor Experimental Biology, 1964, 18,387-400.

PAILLARD, J., 8< BROUCHON, M. Activeand passive movements in the calibrationof the position sense. In S. J. Freedman(Ed.), The neuropsychology of spatiallyo r ie n ted behavior. Homewood, Ill:Dorsey Press, 1968.

POSNER, M. I. Characteristics of visual andkinesthetic memory codes. Journal ofExperimental Psychology, 1967, 75,103-107.

ROSE, J. E., 8< MOUNTCASTLE, V. B.Touch and kinesthesis. In J. Field (Ed.),Handbook of physiology. Section I:Neurophysiology. Vol. 1. AmericanPhysiological Society, 1959.

SIEGEL, S. Nonparametric statistics for thebehavioral sciences. New York:McGraw-Hill, 1956.

S KOGL UNO, S. Anatomical andph ysiological studies of knee-jointinnervation in the cat. Acta PhysiologicaScandinavia, 1956, 36 (SuppI. 124).

TAUB, E., 8< BERMAN. A. J. Movementand learning in the absence of sensoryfeedback. In S. J. Freedman (Ed,), Theneuropsychology of spatially orientedbehavior. Homewood, Ill: Dorsey Press,1968.

WOODWORTH, R. S. The accuracy ofvoluntary movement. PsychologicalReview, 1899, 3 (Monograph Suppl. 3).

(Accepted for publication February 18,1972.)

96 Perception & Psychophysics, 1972, Vol. 12 (lB)