Develop. Med. Child Neuvol. 1968, 10, 697-705

The Applications of Operant Conditioning to the Measurement and Development of Motor Skill

in Children

OPERANT conditioning is the term applied by Skinner to the techniques which he has developed for the analysis and control of behaviour. These techniques have been used extensively and with such considerable success in studying the behaviour of infra- human organisms that they are increasingly being employed in investigating various aspects of behaviour in man. Skinner’s own theoretical position in psychology is a restricted one since he is interested in the prediction and control of behaviour rather than in understanding it. However, with- out adopting Skinner’s theoretical position it is possible to utilise the methods which have been developed in investigating a wide range of problems. The purpose of this paper is to discuss some of the ways in which the techniques of operant condition- ing may be applied to the development of motor skill in children, and to review relevant literature.

The basic concepts and techniques of operant conditioning are relatively simple, though complex notations and a sophisti- cated terminology have been developed. The basic ideas are outlined in Keller and Schoenfeld (1950) and a more detailed treatment of the various areas of research and application is given in Honig (1966).

Kevin Connolly

In essence the experimenter imposes stimuli on the organism in an attempt to bring responses (any movement or action) under stimulus control. The most important stimulus events are the reinforcers which are given when the behaviour under in- vestigation occurs and they serve to strengthen or maintain it. Reinforcers are applied according to certain contingencies or rules called schedules of reinforcement. These schedules exert their control over the temporal patterning of responses ; rates of responding, therefore, can be made to vary over a wide range. Most schedules provide intermittent or partial reinforcement ; this results in the response becoming more resistant to the extinction which follows when reinforcement is withdrawn. Another class of stimuli presented independently of responses are known as discriminative stimuli and serve as cues for a response. The combination of the cueing function of discriminative stimuli and the sustaining effect on behaviour of scheduling the reinforcement allows powerful control to be exerted over the response.

Operant Conditioning and Children The last decade has seen considerable

developments in the application of operant ..-

Department of Psychology, Sheffield University, Sheffizld, 10.

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techniques to the study of behavioural development and the control of behaviour in children. Brackbill (1 958) conditioned smiling in 4-nionths-old infants. She established the operant level (baseline responding) by standing over an infant’s crib but not responding to smiles. During the conditioning trials she reinforced smiles by smiling back at the child and cuddling him. The rate of smiling increased significantly when reinforcement was given and fell below the operant level when it was withdrawn. Rheingold rt al. (1959) have shown, using similar techniques, that the vocalisations of young infants also have operant properties.

A number of studies have dealt with behavioural anomalies and problems. Flanagan et al. (1958, 1959) demonstrated experimental control of stuttering through reinforcement procedures. In one of these studies, stuttering resulted in the subject receiving a 6,000 cps. tone at 105 db. delivered through earphones. Their results shon,ed that the presentation of this tone as a consequence of stuttering weakened the stutter relative to the speech rate. That is to say, stuttering became less frequent. With the situation reversed so that cessation of the tone followed stuttering, the frequency of stutters increased again. These experiments provide adequate evidence that some forms of stuttering at least can be brought under stimulus control. Baer (1962a) reduced thumbsucking in a child by withdrawing positive reinforce- ment. in this case cartoon films, whenever the child put his thumb in his mouth. Ferster (1961) and Ferster and DeMyer (1961, 1962) carefully programmed the tvhoie environment of autistic children and achieved some success in controlling the behaviour of these disturbed children.

Sidman and Stoddard (1967a) have used operant methods in developing techniques for evaluating the behavioural potential of normal and retarded children who are

nonverbal or verbally deficient. This work is also aimed at developing techniques for generating behaviour in children who appear to be functioning below their actual capabilities. Impressive results, which also make a substantial contribution to basic science, are emerging from this work.

One consequence of thinking about problems within an operant framework is that questions become not so much what does the child do but what can he do. Ozer (1966, annotated by Francis-Williams 1967), using the term ‘operant conditioning’ in a rather special sense, examines the learning problems of brain-damaged children, and by applying some of the notions from an operant analysis sets out to assess a child’s ‘true potential’. Implicit in this approach is the healthy idea that many of these children’s learning difficulties may reflect inadequate training techniques and methods of assessment. When stated baldly in this way such programmes as those of Sidman and Stoddard, and Ozer seem eminently sensible but few of the tools currently in use approach develop- mental problems in this way.

A thorough review of operant techniques of measurement and experiment used in work with children is provided by Bijou and Baer (1966).

Operant Conditioning and Motor Behaviour

Surprisingly, perhaps, few attempts have been made to apply operant techniques to the control of motor behaviour in humans and particularly children. Verplanck (1956) has described a series of procedures for the direct application of the variables defining the paradigm for operant conditioning to simple human motor responses, and has shown that humans act very much like experimental animals when they are sub- jected to the same treatments. Sheldon and Bjorklund (1966) have utilised a shaping procedure (discussed in the following

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section) in improving performance on a pursuit rotor task. Their subjects, who were army personnel, were reinforced on different schedules by clicks for being on target. They report improved performances on the task following the shaping pro- cedure, this improvement being largely a reduction in the variability of performance, particularly in subjects with low initial scores. They conclude that the improve- ment obtained is largely a function of improved motivation, the shaping pro- cedure providing an adequate incentive.

Johnston et ul. (1966), in an extremely interesting study, applied reinforcement techniques to developing climbing and play on a climbing frame in a child aged 3 years 8 months. This child engaged in little physical activity and particularly avoided climbing equipment. The method used by Johnston and her colleagues was that of giving or withholding social reinforcement (attention, smiling, verbal encouragement) contingent upon certain responses. Rein- forcement was given initially whenever the child approached the climbing frame and gradually this was restricted to the actual climbing behaviour. The operant level was very low, less than 1 per cent of the child’s total outdoor activity being spent on the climbing frame. Nine days after the reinforcement programme was instituted 67.4 per cent of his outdoor activity was spent on the climbing frame. Changes in behaviour consequent upon the reversal of reinforcement coupled with the generalis- ation of motor responses provide adequate support for the contention that this behaviour was under stimulus control.

Foss (1966) has drawn attention to Hefferline’s work concerning the operant conditioning of small muscle movements and argued that this may provide a basis for applying operant techniques to cerebral palsied children. Hefferline (1958) showed that it was possible to train subjects, using visual feedback, to make a movement of

the masseter muscle so small that they were unable to give any verbal report of the movement. He found also that, with adequate training, subjects could continue to produce the selected response in the absence of visual feedback, when only kinesthetic* feedback was available. The visual feedback was obtained by amplifying muscle action potentials and displaying them on a voltmeter. The kind of feedback has been suitably termed ‘augmented feed- back‘ by Foss. Hefferline et ui. (1959), who employed an avoidance conditioning procedure, used, with equal success, re- sponses from the thenar eminence (ball of the thumb), sometimes referred to as the invisible thumb twitch. The response was conditioned to avoid and escape a 60 cps. tone imposed on music. Again, following conditioning and extinction, subjects were unable to report what the effective response had been; they were not aware that they had terminated the aversive condition. In subsequent studies, Hefferline and Keenan (1961, 1963) investigated the gradient of response generalisation and showed that response ranges of amplitudes greater than the reinforced one tended to increase during conditioning and decrease during extinction. More recently Sasmor (1966) worked with individual small scale muscle action potentials within three 10 microvolt ranges in order to analyse the responses more precisely. His findings replicate those of Hefferline and his colleagues.

The important finding reported by Hefferline in his first paper regarding the transfer of control from the visual to the kinesthetic modality was replicated in a different study (Hefferline and Perera 1963). They cued the thumb twitch to a 1,000 cps tone of 500 msec. duration. and established a high level of responding, then system- atically faded the tone out and found that the subject continued to respond to a high

*Kinesthesis in this paper is taken to include muscle, joint and tendon sensation.

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level in the absence of the auditory cue. This finding. that a muscle response established by feedback in the visual or auditory modality can be transferred to proprioceptive control by a suitable train- ing programme. could be of very con- siderable importance in applying operant techniques to training cerebral palsied children.

Applications of Operant Techniques to the Development of Motor Skill

Skilled motor behaviour is characterised by rapid and accurate movements in space. such responses rely upon the accurate reception of information, the processing of this information, the controlled program- ming of muscle movements and the feed- back from these movements so that performance may be monitored and adjustments made. Everyday responses, such as picking up cutlery, are so common and overlearned that we tend to under- estimate the precision of the human operator. However, watching a very young child trying to feed hiinself with a spoon, or reflecting on one’s early efforts in learning to drive a motor car, are very revealing and make it easier to appreciate the complex series of events in any skilled response. The feedback which is so essential to any skilled response may be in several modalities but kinesthesis is always involved. Inadequate feedback invariably results in the impairment of motor responses, and this may very well be a common difficulty experienced by the cerebral palsied child. If feedback from motor responses can be amplified to in- crease the signal-to-noise ratio and so remove distortions then more adequate motor learning may be possible.

There are of course many complications in working with brain-damaged children. Attempting to perform a task at which one is rarely, if ever, successful is not a very rewarding activity and most adults, let

alone children, quickly extinguish. This is very apparent in the case of the hemiplegic child who tends to use his ‘good arm’ and ignore the damaged one. Any situation devised for training these children there- fore must not only allow the experimenter to manipulate the relevant variables ade- quately but must also provide the child with information about his performance and motivate him by providing adequate rewards. As Bilodeau and Bilodeau (1961) point out in their review of motor skills, learning, feedback or knowledge of results has three functions : reward, information and motivation. Any system devised for training children must therefore provide all these.

As part of a research project on the development of motor skill in children we in this laboratory have been applying operant techniques to the measurement and training of skilled motor responses. Our initial task has been to design and build equipment which enables us to shape and measure graded movements, in this case hitting a target. Shaping may be briefly described as the modifying of behaviour by defining a desired response and reinforcing closer and closer approx- imations to this pattern. The task in question was a relatively simple one, and required the child to move his fingers, in response to a signal, from a start button and to hit a target in a fixed position. This apparatus is shown in Fig. 1. For the child it is essentially a clown’s face with a large bright red button fixed to the base some 9 inches in front of it. The nose, which is very large-16 square inches-is referred to as the target area and further subdivided into correct and incorrect sections. Initially the incorrect area is a thin annulus around the large central, correct, area but this may be progressively changed, the correct decreasing while the incorrect area increases.

Two kinds of response shaping are

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Fig. 1, a and b. Young child operating the clown apparatus. (a) Prior to response. (b) Completion of correct response; reinforcement is now being delivered and the clown’s eyes have lit up. Programming, recording and timing equipment can be seen on console to the left of the picture; this is normally some distance from the child.

involved. In order to shape a response some approximation to it must exist in the child‘s behavioural repertoire ; hence the importance of providing a very large target in the early stages of the programme. Once the basic response is established the size of the correct area is progressively reduced by small amounts until the child can reliably hit a small target. This spatial or topographical shaping needs to be distinguished from temporal shaping. Given unlimited time in which to execute the movement most children, even those with impaired control, would be able to hit quite a small target. Motor skills have two compensatory components, accuracy and speed; any improvement in accuracy therefore must be considered in terms of the time taken to produce the response. This temporal shaping is accomplished by using reinforcement contingencies ; the time allowed for the child to make the response and receive the reinforcement is system- atically reduced.

One important problem is that of finding a suitable reinforcer. In animal studies biological reinforcers are typically used, their efficacy being assured by deprivation -food and water are on the whole adquate reinforcers for a hungry rat. It is clearly impossible to use deprivation con-

ditions in work with children and this has led to the development of highly specialised techniques. Basically what is required is a distinctive procedure yielding reinforcing stimuli which retain their reinforcing properties over protracted investigations. A wide range of reinforcers have been used with children; sweets, toys. tokens and so forth. Sweets, which seem on the face of it very promising, pose special problems. Parents worry about dental health, experi- ments have to halt for reinforcer con- sumption and children are by no means resistant to satiation. Ferster and De Myer (1961) have shown that a variable reinforcer is effective in sustaining per- formance over long periods, and social reinforcement is known to be effective with young children. The system we have adopted is a combination of both. When the child makes a correct response, this is signalled by the nose light going out, the clown’s eyes flash and any of a wide variety of verbal messages is uttered by the clown. These messages, uhich are tape- recorded, comprise statements such as, ‘well done’, ‘do that again Johnny’, and laughter. They issue from a speaker positioned behind the clown’s mouth, and may be programmed on different rein- forcement schedules by a programming

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*/a y *€>

. .- -4 -

Fig. 2

unit. There are two advantages to tape- recording the reinforcement : it can be automatically programmed and the variability introduced by the variety and subtlety of the human voice is kept con- stant over sessions (Baer 1962b).

When the child makes an error no reinforcement is provided but an error signal (pure tone of two seconds duration) is issued. Fig. 2 is a flow diagram showing the logic of the system.

In addition to the total number of responses, the rate of responding and the number of correct responses, two other functions are measured. They are : the child's reaction time-time between the nose lighting up and the child lifting his fingers; and the flight time-time between the movement beginning and reaching the target area. Improvements in performance may occur principally as a reduction in the variability of successive responses. The time required to hit a smaller target is greater than that required to hit a larger one. This increase in time may reflect an increase in reaction time (a more difficult response may require more time to pro- gramme) or an increase in flight time (greater time being required to execute a more difficult task) or of course both. Knowing something of how these com- ponents vary as development proceeds in normal chldren may be of great import- ance in understanding the functional nature of the brain-damaged child's difficulties.

The clown apparatus should provide

Fig. 2. Flow diagram showing the sequence of events as a child operates the apparatus. The diagram shows a continuous loop; a sequence of trials would logically end at the re-entry to the start position. Re-instructions 1 and 2 refer to the reiteration of the instruction previously given; ( I ) need to lift fingers, (2) need to hit target area.

Diamond-shaped boxes = decision points. Round-ended boxes = subject-machine inter-

actions. Rectangular boxes -:= internal functions of

machine. RF = reinforcement. Vis. - visual. Aud. auditory.

. .- ~~~~~ ~.

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sufficient information to decide on the feasibility of bringing the motor responses of impaired children under stimulus control. However, as a teaching, as distinct from measuring, device it may be of limited value. Kinesthetic feedback is necessary for the fine control of motor responses and it does not seem unreason- able to postulate that one of the problems confronting cerebral palsied children is inadequate kinesthetic feedback. The problem then is one of devising ways of augmenting feedback such that the child can learn to discriminate signaI from noise. If motor responses can be brought under control by amplifying feedback in another modality (visual) then it might be possible to shift the control to kinesthesis by suitable training procedures. Heffer- line’s work suggests that this may be possible, but it is almost certain to be difficult.

Annett (1959), in a series of experiments in which subjects were required to learn to reproduce a precise pressure, trained one group of subjects with visual feedback provided on an oscilloscope. With the aid of this supplementary cue the subjects learned to perform the task accurately during the training trials, but on removal of the cue they immediately produced responses which were less accurate than those of another group who learned the task without it. Within a few trials they were in fact pressing at about twice the required pressure. Annett discusses several possible explanations for this, one of which is that subjects tend to rely on ‘good’ cues and perform poorly when these are removed. Given visual feedback, then, subjects can learn to perform accurately, but the monitoring of performance appears to be done almost entirely within the visual system and in the normal course of events no equivalence within the kinesthetic system develops.

The problem then becomes one of how

to develop an equivalence between the visual and kinesthetic analyzers of the central nervous system. This is a problem which might be tackled by using operant techniques. We have to establish control over a response by giving visual feedback and then use this feedback to teach the child to identify an equivalent kinesthetic signal and discriminate this from noise.

In discrimination learning the analogue of response shaping is stimulus shaping. The teacher starts by reinforcing a stimulus- response relationship which the learner has acquired, or can easily acquire, and gradually changes the stimuli until he arrives at the restricted stimulus-response relationship he wants to teach. Terrace (1963a, b) used stimulus shaping or fading to teach stimulus-response relations to pigeons. He began with birds that pecked an illuminated key and did not peck it when it was not illuminated. He then transferred the basis for the discrimination by gradually fading colours on the key so that the pigeons would peck the key when it was red but not when it was green. Further shaping was achieved by super- imposing lines on the coloured key and then gradually fading out the colours. In this way the birds were taught to peck the key when it had a vertical line on it and not peck it when the line was horizontal.

Sidman and Stoddard (1967b) have used a fading technique in teaching retarded children aged from 9 to 15 years to discriminate circles from ellipses. This was done by establishing a brightjdark dis- crimination, then fading in a form/no form discrimination and when this was estab- lished fading in the circle/ellipse discrimin- ation. The effectiveness of this technique impressed me greatly when I witnessed my own young daughter, then aged 25 months, put through this programme. I was im- pressed, not only that she learned the discrimination, but at the speed and seeming ease with which she did so.

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Failure, or great difficulty, on the part of a child to learn a given response has frequently been accounted for in terms of the child’s not being ready, or not being able. to learn the response at that time. Clearly, we should also ask about the efficacy of our teaching techniques.

The problem of transferring control from visual to kinesthetic feedback in cerebral palsied children is undoubtedly a complex one but as Foss points out this may well be predominantly an engineering problem. We are at present engaged in devising an apparatus which will enable us to attempt this transfer. Working with a simple graded movement in one plane, we are attempting to bring this response under control by providing visual feedback. Once this is accomplished the more difficult task of fading out the visual feed- back has to be undertaken. A number of possible methods are being considered. amongst them providing progressively delayed feedback or introducing a pro- gressive lag into the visual feedback.

Similar constraints govern this approach as were applied to the clown, namely, it

must provide information and motivation. It is therefore conceived as a game which tells the child when he is correct, and when he is incorrect. So far this equipment is still on the drawing board but the idea involved appears a viable one on the basis of Hefferline’s work.

The problems are considerable. The development of equipment takes a great deal of time and money before the human difficulties of fitting the child into the ‘man- machine’ system are met. The need however is great. The purpose of echoing Foss’s rri de coeur is to suggest other ways in which operant conditioning may be used to aid the brain-damaged child and hope that the interest of other workers is stimulated.

Acktiowledgements: This work forms part of a research programme on the development of motor skill in children which is supported by a grant from The Spastics Society. Thanks are due to Sandy Cohen who is collaborating in this in- vestigation, to Max Sime for help in designing suitable circuits, to Eric Eagle, Alan Newton and Bill Dyson who built the equipment described and to my daughter Oona for valiantly playing with the clown at various stages in its development, even when it showed a reluctance to respond.

SUMMARY The principles and techniques of operant conditioning are described, and some attempts

to apply operant conditioning to the control of motor behaviour in children are reviewed. The author describes an apparatus on which a child is led to hit a progressively smaller target. while his responses and reaction-time are measured. It is hoped that this apparatus will provide information on the feasibility of controlling the motor responses of handi- capped children.

RESUME L‘applicarion du ronditiortnemetit operant a la inesure et au dkveloppement de l’habilett

motrice dtei les enfants L’auteur d6crit les principes et les techniques de conditionnement ‘operant’ et passe en

revue quelques tentatives &application au contrhle du comportement moteur des enfants. II dicrit un appareil par lequel un enfant est amen6 a frapper une cible de plus en plus petite, pendant que ses reponses et son temps de reaction sont mesures. On espkre que cet appareil fournira des informations sur la possibilite de contr6ler les riponses motrices des enfants handicappes.

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RESUMEN La aplicacidn del acondicionamiento ‘operant’ a la medicidn y evolucidn de habilidades

motoras en nifios Se describen la teoria y la tCcnica del acondicionamiento ‘operant’, y se revisan algunos

esfuerzos para aplicar Cste a1 control del comportamiento motor en niiios. El autor describe un aparato que conduce a1 niiio a dar en un blanco cada vez mhs pequeiio, mientras que se determinan sus respuestas y su tiempo de reacci6n. Uno de 10s objetivos de dicho aparato es obtener informes sobre la posibilidad de controlar las respuestas mot.oras de niiios afectos de incapacidades.

REFERENCES

Annett, J. (1959) ‘Learning at pressure under conditions of immediate and delayed knowledge of results.’ Quart. J. exp. Psychol., 11, 3.

Baer, D. M. (1962a) ‘Laboratory control of thumbsucking through the withdrawal and representation of reinforcement.’ J. exp. Anal. Behav., 5, 525. - (1962b) ‘A technique of social reinforcement for the study of child behaviour: behaviour avoiding

reinforcement withdrawal.’ Child Develop., 33, 847. Bijou, S. W., Baer, D. M., (1966) ‘Operant methods in child behaviour and development.’ In Honig, W. K.

(Ed.) Operant Behaviour : Areas of Research and Application. New York: Appleton-Century-Crofts. Bilodeau, E. A., Bilodeau, I. McD. (1961) ‘Motor skills learning.’ Ann. Rev. Psychol., 12,243. Brackbill, Y . (1958) ‘Extinction of the smiling response in infants as a function of reinforcement schedule.’

Child Develop., 29, 115. Francis-Williams, J. (1967) ‘Operant conditioning in evaluating children with learning problems.’ Develop.

Med. Child Neurol., 9. 350 Ferster, C. B. (1961) ‘Positive reinforcement and behavioural deficits in autistic children.’ Child Develop.,

32, 437. - De Myer, M. (1961) ‘The development of performances in autistic children in an automatically con-

trolled environment.’ J. chron. Dis., 13, 312. Flanagan, B., Goldiamond, I., Azrin, N. (1958) ‘Operant stuttering: the control of stuttering behaviour

through response contingent consequences.’ J. exp. Anal. Behav., 2,173. _ _ - (1959) ‘Instatement of stuttering in normally fluent individuals through operant procedures.’ Science, 130, 979.

Foss, B. M. (1966) ‘Operant conditioning in the control of movements.’ Develop. Med. ChiU Neurol., 8, 339. Hefferline, R. F. (1958) ‘The role of proprioception in the control of behaviour.’ Trans. N. Y. Acud. Sci., 20,

739. - Keenan, B., Harford, R. A. (1959) ‘Escape and avoidance conditioning in human subjects without their

observation of the response.’ Science, 130, 1338. _ - (1961) ‘Amplitude-induction gradient of a small human operant in an escape-avoidance situation.’ J. exp. Anal. Behav., 4, 41. _ _ (1963) ‘Amplitude-induction gradient of a small scale (covert) operant.’ J. exp. Anal. Behav., 6, 307. - Perara, T. B. (1963) ‘Proprioceptive discrimination of a covert operant without its observation by the

subject.’ Science, 139, 834. Honig, W. K. (ed.) (1966) Operant Behaviour: Areas of Research and Application. New York:

Appleton-Century-Crofts. Johnston, M. K., Kelley, C. S., Harris, F. R., Wolf, M. M. (1966) ‘An application of reinforcement

principles to development of motor skills of a young child.’ Child Develop., 37, 279. Kell.er, F. S., Schoenfeld, W. W. (1950) Principles of Psychology. New York: Appleton-Century-Crofts. Ozer, M. N. (1966) ‘The use of operant conditioning in the evaluation of children with learning problems.’

Clin. Proc. Child. Hosp. (Wash.), 22, 235. Rheingold, H. L., Gewirtz, W. C., Ross, H. W. (1959) ‘Social conditioning of vocalisations in the infant.’

J. comp. physiol. Psychol., 52, 68. Sasmor, R. M. (1966) ‘Operant conditioning of a small scale muscle response.’ J. exp. Anal. Behav., 9, 69. Sheldon, R. W., Bjorklund, J. F. (1966) ‘Pursuit rotor performance. I. Effect of reinforcing the longer

intervals of continuous tracking within each trial.’ HumRRO. Technical Report, 66-1 1. Sidman, M., Stoddard, L. T. (1967a) ‘Programming perception and learning for retarded children.’ In

Ellis, N. R. (Ed.) International Review of Research in Mental Retardation. Vol. 2. New York: Academic Press.

retarded children.’ J. exp. Anal. Behav., 10, 3. _ _ (1967b) ‘The effectiveness of fading in programming a simultaneous form discrimination for

Verplanck, W. S. (1956) ‘The operant conditioning of human motor behaviour.’ Psychol. Bull., 53, 70.

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