JOURNAL OF APPLIED BEHAVIOR ANALYSIS

A SYNCHRONIZATION EFFECT AND ITS APPLICATIONTO STUTTERING BY A PORTABLE APPARATUS'

N. AZRIN, R. J. JONES, AND BARBARA FLYE2

ANNA STATE HOSPITAL AND SOUTHERN ILLINOIS UNIVERSITY

The present study attempted to determine how a rhythmic beat affects ongoing behavior.A regular stimulus beat was presented to normal subjects who had been instructed to pusha bar from side to side. Other subjects had been instructed to emit a vocal response. The indi-vidual vocal and motor responses became synchronized with the individual beats of therhythm. The time between stimulus beats determined the modal interresponse time. Theseresults indicate a synchronization effect: ongoing behavior tends to become synchronized withan ongoing stimulus rhythm. An attempt was made to apply these findings to the problem ofstuttering, which can be considered as a disturbance of the natural rhythm of speech. Stutter-ers were instructed to synchronize their speech with a simple regular beat presented to themtactually by a portable apparatus. The result was a reduction of 90% or more of the stutteringfor each subject during the period of synchronization. This effect endured for extendedperiods of spontaneous speech as well as for reading aloud and was found to be attributableto the rhythmic nature of the stimulus and not to other factors.

EXPERIMENT I: CONTROL OF SIMPLEMOTOR AND VOCAL RESPONSES

BY RHYTHM

Rhythmic stimuli are believed to exert sub-stantial behavioral influence, as evidenced bythe extensive natural use of music. Yet, thebasis of this control by music remains unex-plained. One known property of music is thatwhen music is contingent upon a response itcan be a reinforcer, as shown by Barrett's(1962) punishment of tics by timeout frommusic and by Ayllon and Azrin's (1965, 1968a,1968b) reinforcement of adaptive behaviorsof chronic mental patients in their token rein-forcement system. Loud music has been foundto act as a punisher (Smith and Curnow, 1966)and is similar in that respect to the effect of

"This study was supported by the Mental HealthFund of the Illinois Department of Mental Health andby NIMH Grant MH04926. Grateful acknowledgmentis given to T. Ayllon, H. Rubin, and D. F. Hake forcontinuing advice and assistance, to R. Campbell, I.Goldiamond, R. Laws, S. Pace, and G. Siegel, for ad-vice or assistance at various specific points, and toD. Sauerbrunn for constructing the apparatus. Reprintsmay be obtained from N. Azrin, Behavior ResearchLaboratory, Anna State Hospital, 1000 North Main St.,Anna, Illinois 62906.2Now at Drexel Institute.

simple noise on human behavior (Azrin, 1958).Even when it is not contingent on behavior,music seems to have distinctive properties; theGSR and respiration have been found toincrease during some types of music and todecrease during others (Zimny and Weiden-feller, 1962, 1963; Ellis and Brighouse, 1952).Also, the use of music therapy for mentalpatients seems to be based on the assumptionthat music affects the general emotional state.Non-contingent music has often been reportedas increasing the level of ongoing behaviors,but these reports are often conflicting (seereview by Uhrbrock, 1961). Even when a com-plex musical sound pattern affects ongoingbehavior, the question remains as to whichaspect of the complex was responsible. Thepresent study attempted a more analytic studyof the effect of rhythm by investigatingwhether a simple regular beat influenced on-going behavior. The procedure differed fromprevious studies of rhythm in that the responsewas a simple and discrete movement of abar or a simple vocal response, rather than acomplex behavioral sequence; similarly, therhythmic stimulus was a fixed beat rather thana complex musical pattern. The simple natureof the response and the stimulus permittedthe evaluation of any point-to-point corre-spondence in time between them and the eval-

283

1968, 1.,283-295 NUMBER 4 (WINTER 1968)

N. AZRIN, R. J. JONES, and BARBARA FLYE

uation of any change in the overall rate ofresponse.

METHOD

SubjectsTwenty six high school or college students

14 to 22 yr who responded to an advertisementwere used. Each subject served for one-half orone full day and was paid $1.50 per hour.

ApparatusThe subject was seated in a sound-proofed

room at a table on which was located a con-sole containing the motor-response apparatusand the stimuli. A red light served as a signalto work; the subject was to rest when it wasnot illuminated. The motor-response appara-tus was a movable bar. This response bar, 7-in.long, could be moved from side to side over a1800 arc, at both limits of which a briefbuzzing sound, about 70 msec in duration,provided response feedback. About one poundof force was required to move the bar. Toinsure that the subject used only one hand inmoving the response bar, a lever was locatedon the left side of the console; response feed-back for moving the response bar resultedonly if the subject also had been holding thislever down. The verbal response apparatuswas a Lavalier microphone, worn on thechest, the output of which activated a voice-operated relay. Because of the closeness of themicrophone to the subject's mouth, the relaywas especially sensitive to vocal sounds andinsensitive to nonvocal sounds. A small pilotlight on the console flashed for 70 msec at theonset of each vocal response, thereby providingfeedback to the subject that the response wassufficiently loud. A sound-light combinationwas used for the stimulus beat. The soundwas a 1000-Hz tone of 80-db intensity; thelight stimulus was provided by two 3-in.diameter translucent windows on the consolethat were backlighted by 7-w lamps. The over-head illumination was fairly dim and wasprovided by a 25-w bulb shining through asmoked glass shield so as to give prominenceto the visual portion of the rhythmic stimulus.A fan provided air movement and resulted inan ambient noise level of 60 db. The schedul-ing and recording equipment was located ina different room; the subject was alone exceptduring the instruction period.

InstructionsThe following instructions were read to

the 16 subjects assigned to the motor-responseapparatus:

"Your job is to test this equipment. Itworks in the following way: hold thelever down with your left hand and movethe stick back and forth to sound thebuzzer. Hold, do not throw, the stick.The equipment turns off when the worklight goes off. The work light is the small,red light mounted on the console. It willprobably go off quite soon since it's onnow. This will happen every 10 or 15minutes. You may rest during this time.When it comes back on, resume working.Usually the light and tone flash on andoff (both are continuous and uninter-rupted during the instructions). Pleaseremain in the room until I return".

The instructions for the 10 subjects giventhe verbal-response apparatus were the sameexcept for the response description whichwas:

"Say the word 'Do' loudly and distinctly.This voice light (pointing) goes on whenthe word is loud enough".

Only one subject asked how fast she was towork; she was told to work at whatever rateshe wished.

ProcedureThe experimental design consisted of three

separate procedures, each of which used differ-ent subjects. The first procedure used sixfemale subjects and compared performanceof the motor response in the presence of therhythm with performance in its absence. Thestimulus rhythm was presented during alter-nate 1-hr periods of a 6-hr session. Duringthe rhythm periods the stimulus was presentedevery 1.1 sec; the duration of each stimulusbeat was 0.1 sec. During the intervening 1-hrperiods in which the rhythm was absent, thestimulus light and tone were uninterrupted;the tone sounded continuously and the lightwas illuminated continuously. The sessionbegan with the rhythm absent.The second procedure used 10 female sub-

jects and determined whether two differentrhythms produced different behavioral effects

284

SYNCHRONIZATION APPLIED TO STUTTERING

on the motor response. The subjects weregiven the stimulus every 0.9 sec during half ofthe 6-hr session and every 1.3 sec during theother half. Half of the subjects received the1.3-sec rhythm in the morning; the other halfreceived that value in the afternoon.The third procedure used 10 subjects, five

females and five males, and determinedwhether two different rhythms produceddifferent behavioral effects on the vocalresponse. The subjects were given the stimulusevery 0.6 sec during half of the 2-hr sessionand every 0.9 sec during the other half. Halfof the subjects received the 0.9-sec rhythmfirst. All subjects were given one session. The6-hr sessions were interrupted by a 30-minlunch period after the third hour; the 2-hrsessions were interrupted by a 1-hr rest periodafter the first hour. During all sessions, thework light was disconnected every 15 minfor 1 min, during which the experimenterrecorded the counter readings in the adjacentroom while the subject was not responding.

RESULTS

The rhythmic stimulus produced a slightchange in overall rate of the motor response ascompared with the absence of a rhythm. Themean response rate was 56 per min during the

1.1-sec beat and 62 per min without the beat.All six subjects had a lower rate of responseduring the rhythm, but for none of them wasthe response rate changed more than 16% bythe rhythm. This difference was statisticallysignificant (P < 0.05) by the Wilcoxin non-parametric matched-pairs test (Siegel, 1956).Similarly, a slight increase in rate resultedfrom the faster rhythm for the other nine sub-jects (a failure of the recording apparatusoccurred during the 0.9-sec beat for the tenthsubject). The mean response rate was 71 permin during the faster rhythm (0.9-sec beat)and 58 per min during the slower (1.3-secbeat). The difference in response rate exceeded20% for five of the subjects and was reversedin direction for three subjects. This differencewas not statistically significant. For the vocalresponse, the mean response rate was 58 permin during the faster rhythm (0.6-sec beat)and 52 per min during the slower (0.9-secbeat). This difference was not statisticallysignificant.

Figure 1 shows how the motor responseswere spaced in time for the six subjects whoreceived the comparison between the rhythmand no-rhythm conditions. Synchronization ofthe behavior with the rhythm would be shownwhen the interval between responses (inter-response time) was equal to the interval be-

1.1 SEC. INTERSTIMULUS TIME

*

N-6

I a I a I0 . 1. 0.

0.5 1.0I.

1.5 1.9+ 0

I NTERRESPONSE

CONTINUOUS STIMULUS

_ Nz 6

. . . . ... . . . .. . . . ....- J -ATIME (SECONDS)

Fig. 1. The distribution of time intervals between responses for six subjects. In the left graph, a stimuluswas presented every 1.1 sec. The arrow designates the interresponse time that coincides with the interstimulustime. In the right graph for the same six subjects, the stimulus was continuous and steady with no beat. Thetimes between responses were recorded in 100-msec class intervals up to 1.9 sec. The data point on the ex-treme right of each graph includes all interresponse times greater than 1.9 sec. Each data point is the number ofresponses during a 3-hr period averaged for the six subjects.

U)wU)z00LU)LiJ

cn

z

u-Ut-U)

cr

co

aooo-

2000-

1,000-

A

0 1.9 +

285

'Aft

9IIvwviIvI01

M 1.0 1.5

N. AZRIN, R. J. JONES, and BARBARA FLYE

tween stimulus beats. In the absence of thebeat, the interresponse times were distributedfairly broadly from 0.5 sec to 1.1 sec with asingle mode at 0.7 sec. During the 1.1-sec beat,the distribution became bimodal, with theprincipal mode precisely at the value of theinterstimulus interval (1.1 sec). The curvesfor individual subjects (not shown here)resembled the averaged data of Fig. 1 in thatthe modal interresponse time was identical tothe interstimulus time of 1.1 sec for five ofthe six subjects during the stimulus rhythmic,but differed from 1.1 sec for all subjects inthe absence of the rhythm. The slight second-ary mode at 0.7 sec seen in the averaged curvewas caused by the sixth subject, who exhibitedno synchronization with the stimulus.

Figure 2 shows the interresponse-time dis-tribution for the motor response averaged forthe 10 subjects given the 0.9-sec and 1.3-secstimulus beat. Consider first the 0.9-sec beatin the left portion of the figure. At the 0.9-sec beat, a bimodal distribution resulted withthe principal mode coinciding precisely withthe interstimulus interval and the secondarymode coinciding with a duration equal to one-half of that (0.4 or 0.5 sec). The curves for theindividual subjects showed that of seven whohad a single mode, it coincided precisely with

the interstimulus interval of 0.9 sec for fivesubjects and with the half-value for one sub-ject. Three subjects showed two distinctmodes, one of which was at precisely the valueof the interstimulus interval for each of thethree subjects. The second mode was equalto one-half that value for one subject and attwice that value (1.8 sec) for another. Considernow the 1.3-sec beat. The right portion ofFig. 2 shows that a bimodal distribution ofinterresponse times also occurred in theaveraged data during this 1.3-sec beat forthese same subjects. Again, one mode was atthe precise duration (1.3 sec) of the inter-stimulus interval and the second mode at one-half of that duration (0.6 or 0.7 sec). Theindividual curves showed that of seven sub-jects who had a single mode, it was at preciselythe duration of the interstimulus interval (1.3sec) for four subjects, and at one-half thatduration for three subjects. For the singlesubject who had a bimodal distribution, onemode was at the interstimulus interval andthe other at the half-value. The single subjectwho did not synchronize at the 0.9-sec beatalso was the only one who did not synchronizeat the 1.3-sec beat.

Figure 3 shows the interresponse-time dis-tribution for the vocal responses averaged for

w 0.9 SEC. INTERSTIMULUS TIME 1.3 SEC. INTERSTIMULUS TIMEz 4.000-0U)

sr 3,000-

zui 2000 Nz10 N=9

U<1,000-

Q.

0 O- -.., , I,',,,,,;...'......... ....,,,0 0.5 1.0 1.5 129+ 0 0.5 10 1.5 1.9+

co INTERRESPONSE TIME (SECONDS)Fig. 2. The distribution of time intervals between responses for 10 subjects. The response was moving a lever.

The stimulus was presented every 0.9 sec in the left graph and every 1.3 sec in the right graph for the samesubjects except for one subject for whom the recording apparatus was defective during the 1.3-sec stimulusbeat. The arrow designates the interresponse time that coincides with the interstimulus time. The timebetween responses was recorded in 100-msec class intervals. The data point on the extreme right of each graphincludes all interresponse times greater than 1.9 sec. Each data point is the number of responses during a 3-hrperiod and is the average for the 9 or 10 subjects.

286

SYNCHRONIZATION APPLIED TO STUTTERING

0.6 INTERSTIMULUS TIME

N=10

I

0.9 SEC INTERSTIMULUS TIME

N=10

6 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 +

INTERRESPONSE TIME (SECONDS)Fig. 3. The distribution of time intervals between responses for 10 subjects. The response was saying the word

"Do". The stimulus was presented every 0.6 sec in the upper graph and every 0.9 sec in the lower graph for thesame 10 subjects. The arrow designates the interresponse time that coincides with the interstimulus time. Thetime between responses was recorded in 100-msec class intervals. The data point on the extreme right of eachgraph includes all interresponse times greater than 3.9 sec. Each data point is the number of responses duringa 1-hr period and is the average for the 10 subjects.

the 10 subjects. The upper portion of thefigure for the 0.6-sec beat shows five modeswhich correspond precisely with the inter-stimulus interval or with precisely one-half(0.3 sec), twice (1.2 sec), thrice (1.8 sec), or fourtimes (2.4 sec) that value. The curves for theindividual subjects showed that two subjectshad a single mode, three had a bimodal dis-tribution, three had three modes, and twohad four modes. All but two of these modeswere an exact multiple of 1/2, 1, 2, 3, or 4 timesthe interstimulus value. The lower portion ofFig. 3 is for the 0.9-sec beat and shows fourmodes which correspond with an exact mul-tiple of '/,, 1, 2, or 4 times the interstimulus

value of 0.9 sec. The curves for the individualsubjects showed that three subjects had one

mode, five had two modes, none had threemodes, and one had four modes; one subjecthad no distinct mode. All but three of thesemodes were at an exact multiple of 1/2, 1, 2, or

4 times the interstimulus duration. Examina-tion of the curves for individual subjectsrevealed that all 10 subjects showed one or

more types of synchronization of their vocalresponse during the 0.6-sec beat; nine of the10 showed some synchronization during the0.9-sec beat.

Event recordings were taken during thevocal response procedure. Figure 4 shows

1200

U)*LLC,)z0CLu-i

-J

0

287

N. AZRIN, R. J. JONES, and BARBARA FLYE

sample recordings obtained from S-8, who isshown here because she synchronized herbehavior with the beat in several differentways at different times. Straight timing, half-timing, third-timing, and quarter-timing areillustrated.Examination of the individual interresponse

time distributions for each 1 5-min periodshowed that synchronization seemed to en-dure for the entire 3-hr period. For the 10motor-response subjects in Fig. 2, for example,nine synchronized during the first 15 min ofthe 0.9-sec beat and all but one of the nine alsosynchronized during the last 15 min. Similarly,seven of these subjects synchronized during thelast, as well as the first, 15 min-period of the1.3-sec beat. Synchronization is defined hereas a modal interresponse time that is an exactintegral fraction, or multiple, of the inter-stimulus interval.

S-8I I I I I I I

VOCA , I I IlI I I I I s I

RESPO NS III I I I'll

STIMULUS l11 11111111111111

0.6 SEC

(1/4)(1/2)(1) (1/2)

I'd' I I I (1/4)VOCAL u un m mm ()/3

RESPONSE\ \.. ,,,*,*,*,*,,, ()STIMULUS fli ll',t "m"imi"

0.9 SECFig. 4. Sample event recordings of the vocal responses

of one subject at different times during a single session.The tone-light stimulus occurred every 0.6 sec in theupper portion of the figure and every 0.9 sec in thelower portion. The vocal responding was recorded asthe output of a voice-operated relay; only the onset ofeach vocal response actuated the recording pen. Thenumbers to the right designate the type of synchroniza-tion occurring between the responses and the stimulusbeat for each time period.

DISCUSSION

The results showed that for the motorresponses, the rhythm slightly decreased theoverall rate of responding relative to the rateof responding in the absence of the rhythm.This slight change of overall performance is ingeneral agreement with most previous studiesof non-contingent music which also found nosubstantial change in ongoing performance(Smith and Curnow, 1966; Freeburne andFleischer, 1952; Newman, Hunt, and Rhodes,1966; and review by Uhrbrock, 1961). The

present results also indicated a slightly higherrate of motor responding during the fasterrhythm for some subjects. Some previous com-parisons of different types of music have alsoreported very slight differences in perform-ance levels during one of the musical pieces(i.e., Freeburne and Fleischer, 1952) but con-clusions about the speed of the rhythm arenot possible in such studies because the musi-cal pieces were different on several other quali-tative dimensions. The present difference inresponse rates can be attributed only to thequantitative difference in the rate of stimuluspresentation because the rhythms were other-wise identical.A possible basis for the change of the overall

rate of response was seen in the detailedanalysis of the temporal distribution of theresponses. For all but three of the 26 subjects,the responses tended to synchronize with therhythmic beat; this synchronization did notdecrease during the period of presentation.The simplest form of synchronization was alsothe most common; one response was made foreach stimulus beat. Synchronization also tookthe form of double-timing, half-timing, third-timing, and quarter-timing, wherein a responsewas made on every nth beat as evidenced bymodal interresponse times that were an inte-gral multiple of the interstimulus interval.Thus, the overall rate of response could eitherdecrease or increase depending on which formof synchronization was present or dominant.The major finding of this study was the

synchronization effect which may be gen-erally described as a tendency for ongoingmotor and verbal responses to become syncho-nized with, or to occur in phase with, an on-going stimulus rhythm. The phenomenon wasnot restricted to a particular rhythm sincesynchronization occurred at the four differentrhythm values of 0.6, 0.9, 1.1, and 1.3 beatsper sec. This spontaneous synchronizationeffect has not been investigated and reportedpreviously. A critical feature of the presentstudy is that the synchronization effectoccurred without any instructions to the sub-jects to attend to the rhythm. Nor did thesubjects indicate verbally any implicit beliefthat they should synchronize their behaviorwith the rhythm. Subjectively, the reaction ofthe experimenters while testing the apparatuswas that it was difficult to avoid synchroniza-tion; the beat seemed to "pull" the behavior

288

SYNCHRONIZATION APPLIED TO STUTTERING

into phase with the beat. Dancing, marching,and singing appear to be examples of naturalbehaviors in which this synchronization effectoperates. It is possible that the high naturalfrequency of these behaviors and their use as

therapeutic aids in recreational therapy are

based in part upon this tendency for behaviorto be "carried along" by a rhythm. A recentexample of this rationale is a therapeutic pro-

gram in which rhythmic activities were

described as a necessary and effective startingpoint for motivating chronic regressedschizophrenics (Goertzel, May, Salkin, andSchoop, 1965).

EXPERIMENT II: THE EFFECT OF AVIBROTACTILE RHYTHM

ON STUTTERINGExperiment I showed that ongoing motor

and vocal responses tended to synchronizewith an ongoing rhythmic stimulus. This find-ing might have practical utility in eliminatingbehavioral disorders characterized by a dis-turbance of rhythm. One such disorder seems

to be stuttering, in which the natural speechrhythm is disturbed. The synchronization effectof Exp. I suggested an application to stutteringby synchronizing individual verbal units, suchas words or syllables, with an ongoing rhythm.Indeed, such a procedure has long been known(see discussions by Bloodstein, 1949; Beech,1967; Fransella and Beech, 1965) in which a

stutterer is instructed to speak in time withan auditory metronomic beat; the result hasbeen a reduction of stuttering. Yet, almost no

quantitative study has been conducted of thismetronomic effect since an early study byBarber (1940) dismissed the effect as an in-stance of "distraction" of attention. An excep-tion is the recent work by Fransella and Beech(1965). The procedure has gone unmentionedin several recent treatments of stuttering andof speech disorders generally (Hejna, 1960;Travis, 1957; Rieber and Brubaker, 1966;Murphy and Fitzsimons, 1960; Freund, 1966).As noted by Meyer and Mair (1963), the prob-able reasons for the lack of attention to thismetronome effect may be simple lack of knowl-edge about the phenomenon as well as of itstheoretical basis.The present study attempted to reexamine

this metronome effect with three main objec-tives. First, the study examined the phenome-

non in more detail than has been available inprevious studies. Specific attention was givento the rapidity of onset of the effect, individualdifferences between subjects, durability of theeffect in time, possible carry-over effects upontermination of the rhythm, applicability tospontaneous speech as well as reading aloud,and changes in the overall speech rate. Second,the study examined this metronome effect asan instance of the more general synchroniza-tion effect with the objective of providing theneeded theoretical basis for its existence otherthan as an artifact of distraction. If the reduc-tion of stuttering is attributable to the rhythmitself, then a tactual rhythm should also beeffective, as suggested by the results of Barber(1940), but pulses that are not rhythmic shouldhave no effect on stuttering, as suggested bythe results of Fransella and Beech (1965). Thepresent study, therefore, used a tactual rhythmand an arhythmic comparison procedure. Thethird objective was to provide a practicalmethod of reducing stuttering in the stutterer'snatural environment. Consequently, a port-able apparatus was developed that could beworn inconspicuously by the stutterer andwhich served as the source of the rhythmicstimuli. Meyer and Mair (1963) described aportable apparatus for achieving this sameobjective, and reported that it was useful forthe clinical treatment of stuttering but, unfor-tunately, provided no quantitative data as toits effectiveness. The rationale for developingthe apparatus here stemmed from the behav-ioral engineering approach described else-where (Azrin, Rubin, O'Brien, Ayllon, andRoll, 1968; Azrin and Powell, 1968). The targetbehavior was defined as rhythmic speech andthe specific response was defined as the spokenword. The controlling behavioral event was arhythmic stimulus provided by a portableapparatus so that it could operate continuouslyin the stutterer's natural environment. Thisapplication of behavioral engineering differsfrom the previous ones (Azrin et al., 1968;Azrin and Powell, 1968) in that the controllingstimulus is a discriminative stimulus and notan operant consequence. Operant condition-ing procedures have been found effective inmodifying stuttering (Flanagan, Goldiamond,and Azrin, 1958, 1959; Siegel and Martin,1965a; 1965b; Goldiamond, 1965; Martin andSiegel, 1966a, 1966b; Quist and Martin, 1967).The complete behavioral engineering ap-

289

N. AZRIN, R. J. JONES, and BARBARA FLYE

proach, however, would require an apparatusthat could differentiate stuttering from normalspeech in order to schedule an operant con-sequence automatically for a stuttering re-sponse. Unfortunately, this problem of anapparatus definition of stuttering has not yetbeen solved.

METHODFour male college undergraduates were

selected from 12 respondents to an advertise-ment for participants in a stuttering study.The criteria for selection were that the respon-dent stuttered very noticeably during theinitial interview, that he had reported receiv-ing prior therapy for stuttering, and that hewas available at the desired hours.Two speech tasks were used, both of them

in the presence of an observer seated in thesame room near the subject. The first taskwas similar to those used in previous studiesof stuttering; it consisted of reading aloudfrom a book. The second task differed fromthose used previously; it was designed toapproximate spontaneous speech. The subjectdescribed aloud the contents of a series ofpictures assembled from popular magazines.The subject determined how much time wasspent on each picture. None of the pictures orreading material was presented more thanonce to the same subject.Each of three judges scored the speech

independently from a tape recording for fourof the six sessions in which each subject par-ticipated. One judge scored the speech forthe other two sessions. Each word was scoredas either stuttered or nonstuttered, althoughseveral speech blockages often occurred on asingle word. The response of stuttering wasdefined as an abnormal prolongation, interrup-tion, or repetition of a part of a word or arepetition of a whole word. The followingwritten instructions and examples were givento the judges:

You will be listening to a tape record-ing of a person reading (speaking). Theentire monologue is from the book. (Forthe spontaneous speech task, the judgehad before him a typed transcript of thesession.) Follow the monologue in thebook (transcript) and mark through eachword that can be described by any of thefollowing:

1. The speaker begins to say the wordbut hesitates before completing it (ex-ample-sub--marine).

2. The speaker pronounces any syllableof the word in a prolonged manner (ex-ample-suuuubmarine).

3. The speaker repeats some part ofthe word before completing it (example-su su su su submarine or subma mamarine).

4. The speaker says the word correctlybut repeats the whole word before goingon (example-inside the the submarine)except when a whole phrase is repeated.The tape can be stopped and restarted

by operating the foot pedal. The tape canalso be reversed and replayed if you wishto hear some parts of it more than once.

The first four columns of Table 1 show thesequence of experimental procedures. Duringthe entire first session, the subjects read aloudwithout the rhythmic stimulus; during theentire second session, they engaged in thespontaneous speech task, also without therhythmic stimulus. These two sessions pro-vided a baseline measure of stuttering. Thethird and fourth session provided about 50min of reading and spontaneous speech,respectively, with the rhythmic stimulus pres-ent; a 17-min period without the rhythmicstimulus was given at the start and end of thesession, thereby providing for within-sessionevaluation of the effect of the rhythmic stimu-lus. Session 5 provided a longer period (100min) of reading with the rhythmic pulsepresent to determine whether the effect ofthe rhythm would change in time. This periodwas preceded and followed by 17 min of read-ing without the rhythm. The last session com-pared the effects of (1) the rhythmic stimuluswith (2) the arhythmic stimulus with (3) thestimulus absent in a counterbalanced timesequence. The within-session changes in con-ditions were made by the experimenter with-out interrupting the ongoing speech.

ApparatusAn apparatus was designed that could be

worn conveniently and inconspicuously andthat delivered a rhythmic tactual stimulus.The tactual stimulus was delivered to thebony projection on the wrist (the distal endof the ulna) which was found to be particularly

290

SYNCHRONIZATION APPLIED TO STUTTERING

Table 1

291

Percentage of words stuttered with and without an accompanying tactual rhythm for eachof four subjects while reading aloud or speaking spontaneously during each of six sessions.

Percentage ofWords Stuttered

Session Duration Speech MeanNo. (Minutes) Task Stimulus Condition S-1 S-2 S-3 S-4 S1-S4

1 83 Reading No Stimulus 70 20 16 20 32

2 83 Spont. Speech No Stimulus 69 27 18 9 31

3 17 Reading No Stimulus 75 17 4 17 2850 Reading Rhythmic Stimulus 8 1 0 2 317 Reading No Stimulus 65 20 10 18 28

4 17 Spont. Speech No Stimulus 64 29 19 11 3150 Spont. Speech Rhythmic Stimulus 11 2 1 1 417 Spont. Speech No Stimulus 53 26 14 10 26

5 17 Reading No Stimulus 73 10 5 25 28100 Reading Rhythmic Stimulus 8 1 0 0 217 Reading No Stimulus 62 16 7 21 26

6 17 Reading No Stimulus 71 8 11 20 2817 Reading Arhythmic Stimulus 64 10 23 27 3134 Reading Rhythmic Stimulus 10 1 1 2 317 Reading Arhythmic Stimulus 72 17 10 21 3017 Reading No Stimulus 67 17 13 19 29

sensitive to vibrotactile stimulation. Thevibrator was a bone conductor (SonotoneModel BR1500) with its usual case replaced bya formed plastic covering. The vibrator dia-phragm was connected to a thin, slightly coni-cal metal plate positioned on the projectingbone; a leather watchband held the cone-vibrator assembly in place with the cone underthe band and the vibrator above it as seen inFig. 3. Thin wire connected the assembly to atransistorized circuit (Fig. 11.6 in the G. E.Transistor Manual, 7th edition) contained in aplastic case 9 by 6 by 3 cm that could be wornin the shirt pocket or in a shoulder holster be-neath the shirt such that the entire apparatuswas concealed. The circuit provided a 250-Hz

VIBRATI WATCHhe BAND

CONE

2 INCHES

Fig. 5. The apparatus for transmitting tactual stimulito the wrist of the subject. A regular watchband isworn slightly forward of the usual position such thatthe metal cone presses against the bony projection onthe wrist. The vibrations to the cone are generated bya pocket-worn device (not shown here) that transmitsits signal through the thin wires that are seen to beconnected to the vibrator mechanism.

vibration, which is known to have a low thresh-old of tactual sensitivity (Knudsen, 1928).The apparatus was activated by flipping aswitch on the case which could be accom-plished easily even when the case was worn inthe holster. The apparatus provided a 100-msec stimulus pulse at a rate of 90 pulses permin. The intensity and stimulus rate wereheld constant during the experiment. The in-tensity was adjusted by the subject to a valuethat was tactually perceptible but not audibleat distances greater than 4 in. from the ear.During the arhythmic stimulus condition, thewristband assembly was connected to a sepa-rate scheduling circuit that delivered the stim-ulus pulses at irregular intervals, from 0.3 to1.3 sec apart but still averaging 90 pulses permin; each pulse remained at 100-msec dura-tion.

InstructionsBefore the start of the third session, the

subjects practiced reading aloud in time withthe rhythm for 5 min. Similarly, a 5-minpractice period of speaking in time with therhythm was given before the start of thefourth session. The instructions were to speakone word per pulse unless -he word was toolong, in which case the word was to be sylla-bically divided between pulses.

N. AZRIN, R. J. JONES, and BARBARA FLYE

RESULTS

All subjects followed the instructions withno apparent or stated difficulty. As instructed,they awaited a pulse to initiate a word andthen paused for the next pulse before initi-ating the next word. When a word was long,only one or two syllables were usually spokendurinz a beat, and the remainder during thenext beat. Figure 6 is an event recordingtaken from the tape of one subject and showsthe synchronization of speech with the stimu-lus beat when the stimulus beat was intro-duced.

S-3

STIMULUS 'SPEECH

Fig. 6. Sample event recording of a subject readingaloud at the time that the stimulus beat was intro-duced. The speech pen was activated by the outputof a voice-operated relay. The stimulus is vibrotactileand occurs every 0.9 sec.

Table 1 shows the percentage of wordsstuttered during each condition and withineach session by each subject as well as themean of all four subjects. The data for Ses-sions 1 to 4 are the means of the scores of thethree judges; the scores for the individualjudges were within 5% of the mean scores;for this reason only one judge was used forSessions 5 and 6. When the rhythmic stimuluswas absent during all of Sessions 1 and 2,stuttering occurred on a mean percentage of30% of the words for both reading and spon-taneous speech. When the rhythm was presentduring Sessions 3, 4, 5, and 6, stuttering wasreduced to about 3% of the words. This reduc-tion of about 90% occurred for each of thefour subjects and for the spontaneous speech(Session 4), as well as for reading (Sessions 3,5, and 6). The reduced level of stuttering dur-ing the rhythmic pulse was maintained fromsession-to-session and was as low (2.5%) duringthe 100-min period of Session 5 as it wasduring the 34-min period of Session 6 (3.3%)or the 50-min period of Session 3 (2.8%). Thearhythmic stimulus (Session 6) did not reducestuttering discernibly for any subject duringeither of the two 17-min periods. The foursubjects stuttered to different degrees. In theabsence of the rhythmic pulse, about 70% ofthe words were stuttered by S-1 but less than

30% for the other three subjects. During therhythmic stimulus, stuttering was virtuallyabsent for S-2, S-3, and S-4, being 2% or lessof the words.

Figure 7 shows the intrasession changes instuttering during Sessions 3 and 4. The intro-duction of the rhythmic pulse immediatelyreduced the stuttering, which remained at alow level for the entire 50-min period for boththe reading (upper portion of the figure) andfor the spontaneous speech (lower portion ofthe figure). When the rhythmic pulse wasdiscontinued, stuttering immediately increased

40

W 35.uJ

- 30.

, 25

0 ° 20015

a10z

4w 5.

0

40-

r 35.

30) L.

(O' 25 -

,,0 2S-0

B 0O .

LSJ.z

Lu 5-

NOfITMULUS

NOSTIMULUS

RH YTHMIC NOSTIMULUS STIMULUS

a- A N'4

RHYTHMIC NOSTIMULUS STIMULUS

Nr4

0 10 20 30 40 5O 60 70 80 90

TIME (MINUTES)Fig. 7. The percentage of words stuttered during two

sessions. Each session began and ended with a 17-minperiod during which the tactual stimulus rhythm wasabsent. The tactual stimulus was presented 90 timesper min during the 50-min period in the middle of thesession. The upper graph is for the task of readingaloud; the lower graph for the same subjects is for aspontaneous speech task. Each data point is for a 100-sec period averaged for the four subjects.

292

SYNCHRONIZATION APPLIED TO STUTTERING

and returned to its previous level within 5min. Examination of the intrasession recordsof individual subjects (not shown here) re-vealed this same abrupt decrease of stutteringwhen the rhythmic stimulus was introducedand the abrupt increase when it was termi-nated for each subject within each of the foursessions (Sessions 3 to 6) in which the rhythmicstimulus was introduced and withdrawn.The overall rate of speaking was also

affected by the rhythmic stimulus. Table 2shows the mean number of words spoken perminute in the presence and absence of therhythmic stimulus for both the reading andspontaneous speech for each subject. The datafor a given procedure are based on all sessions,or parts of sessions, in which that procedurewas used. Table 2 shows that for the mostsevere stutterer, S-1, the overall rate of speechwas increased by the rhythm; for the threeless severe stutterers, the speech rate decreased.During the rhythmic stimulus, the number ofwords spoken per minute was somewhat lessthan the number of beats per minute (90).The principal reasons for this discrepancyseemed to be the assignment of syllables rather

Table 2

The effect of the stimulus rhythm on the overall speedof speaking. The mean number of words spoken perminute for each subject.

Reading Spontaneous Speech

Subject Stimulus Stimulus Stimulus StimulusNo. Off On Off On

S-1 21 53 19 47S-2 78 61 62 43S-3 120 74 90 75S-4 70 67 120 59

than words to some beatspauses in speech beforesentences.

and the naturalbeginning some

DISCUSSION

The rhythmic stimulus reduced the stutter-ing of each subject by about 90%, which isroughly comparable to the percentage reduc-tion reported by Barber (1940) who also usedrhythmic pulses. The reduction of stutteringendured for as long as the rhythm was pre-sented: from session-to-session and throughout

a 100-min session of continuous reading or a50-min session of continuous speaking. Previ-ous studies had evaluated this metronomeeffect for less than 5 min under a givenrhythm condition (Barber, 1940; Beech, 1967;Fransella and Beech, 1965). The rhythmicstimulus had an immediate effect on thestuttering; stuttering was reduced during thefirst minute that the rhythm was presented.Little carry-over was seen; stuttering returnedto its former level within 5 min after therhythm was discontinued. The arhythmicstimulus did not reduce stuttering to anydegree for any subject, thereby confirming thefinding of Fransella and Beech (1965) thatarhythmic stimuli did not reduce stuttering.Stuttering was reduced during the spontane-ous speech task as well as during the readingtask. Previous studies had reported data onlyfor reading. The above findings were obtainedfor each of the four subjects. For the onesubject who stuttered on 70% of his words,the rhythm reduced stuttering sufficiently toincrease the overall speech rate. For the otherthree subjects who stuttered on less than 30%of their words, the overall speech rate wasreduced somewhat, since synchronization withthe rhythm did not permit more than 90 wordsto be spoken per minute.The present apparatus and method appear

to hold promise as a practical therapy forstutterers. The magnitude of the reductionof stuttering was substantial, and did notdeteriorate in time, either within a fixedperiod or from day-to-day. The tactual modeof stimulation prevented the interferencewith ongoing sounds that an auditory modewould entail. Similarly, this non-auditorymode allowed the stimulator to be concealedcompletely under clothing, in contrast withthe visible attachment required by the audi-tory mode. Since the rhythmic stimulus wasprovided by a self-powered apparatus, thesubject did not need to provide his ownrhythm by gesture or intonation, a procedurethat occasionally has been used in clinicalpractice (see discussion by Bloodstein, 1949).An apparent disadvantage of the procedure

is that stuttering recurred when the rhythmwas terminated; this problem should be easilysolved by activation of the apparatus duringall speech episodes. A second disadvantage isthe measured quality of the speech; this prob-lem seems unavoidable with this type of stim-

293

294 N. AZRIN, R. J. JONES, and BARBARA FLYE

ulation. A third disadvantage is the slowingof the speech which occurred for three sub-jects; this problem might be reduced partlyby using a faster beat such as used by Barber(1940) and by Fransella and Beech (1965) inparts of their studies.The present use of a rhythmic pulse to con-

trol stuttering was suggested by the resultsof Exp. I which had revealed control of motorand verbal responses by a rhythmic stimulus.Other possible explanations of this effect onstuttering are distraction, slowing down ofthe speech, or auditory masking. The distrac-tion explanation states that the stutterer isdistracted by the rhythmic pulse and stopsstuttering because of the consequent inatten-tiveness to his speech. This interpretation wasoriginally suggested by Barber and seems tobe the most widely held view. Yet Barber'sown data show that the rhythmic "distraction"(Barber, 1940) reduced stuttering far morethan the nonrhythmic ones (Barber, 1939,conditions VI-XIV) indicating that distractionwas not the principal basis for the effect.Similarly, Fransella (1967) found no reductionof stuttering when the subjects were given adistracting counting task, but found a largereduction during the rhythmic beat. Also, thearhythmic pulses did not reduce stuttering, afinding of Fransella and Beech (1965) whichwas confirmed in the present study; both therhythmic and arhythmic pulses are presumablyequally distracting.

Fransella and Beech (1965) tested whetherstuttering might have been reduced becauseof the slowing of the speech but rejected thisinterpretation on the basis of their finding,which confirmed Barber's (1940) finding, thateven a fast rhythmic pulse reduced stuttering,even though this faster rhythm producedmore rapid speech. The auditory maskinginterpretation might seem plausible since non-rhythmic masking sounds are known to reducestuttering (Trotter and Lesch, 1966); thisinterpretation is untenable, however, becausethe tactual rhythm of the present study andthe tactual and visual rhythm of Barber's(1940) study reduced stuttering when noauditory pulses were present. In light of theabove findings, the metronome effect onstuttering cannot be explained as either dis-traction, auditory masking, or a slowing ofspeech. Rather, the pulse rhythm per se seemsto play a distinctive role in reducing stutter-

ing. As stated previously, the neglect of themetronome procedures seems to have resultedin part from a lack of a theoretical explana-tion of its effectiveness, other than as an arti-factual and indirect consequence of suchfactors as general distraction or a slowing ofspeech. The present study provides a possibletheoretical explanation of the reduction ofstuttering by a metronome beat: behavior,verbal or nonverbal, tends to become syn-chronized with ongoing rhythmic stimulation;stuttering can be considered as a deviationfrom the natural temporal patterning ofspoken speech. By deliberately synchronizingspeech with a rhythmic pulse, a regular tem-poral patterning is reinstated.

REFERENCESAyllon, T. and Azrin, N. H. The measurement and

reinforcement of behavior of psychotics. Journal ofthe Experimental Analysis of Behavior, 1965, 8,357-383.

Ayllon, T. and Azrin, N. H. Reinforcer sampling: atechnique for increasing the behavior of mental pa-tients. Journal of Applied Behavior Analysis, 1968,1, 13-20. (a)

Ayllon, T. and Azrin, N. H. The token economy: amotivational system for therapy and rehabilitation.New York: Appleton-Century-Crofts, 1968. (b)

Azrin, N. H. Some effects of noise on human behavior.Journal of the Experimental Analysis of Behavior,1958, 1, 183-200.

Azrin, N. H. and Powell, J. Behavioral engineering:the reduction of smoking by a conditioning ap-paratus and procedure. Journal of Applied Be-havior Analysis, 1968, 1, 193-200.

Azrin, N., Rubin, H., O'Brien, F., Ayllon, T., andRoll, D. Behavioral engineering: postural controlby a portable operant apparatus. Journal of AppliedBehavior Analysis, 1968, 1, 99-108.

Barber, V. Studies in the psychology of stuttering,XV. Chorus reading as a distraction in stuttering.Journal of Speech and Hearing Disorders, 1939, 4,371-383.

Barber, V. Studies in the psychology of stuttering,XVI. Rhythm as a distraction in stuttering. Journalof Speech and Hearing Disorders, 1940, 5, 29-42.

Barrett, B. H. Reduction in rate of multiple tics byfree operant conditioning methods. Journal of Ner-vous and Mental Disease, 1962, 135, 187-195.

Beech, R. Stuttering and stammering. Psychology To-day, 1967, 1, 49-63.

Bloodstein, 0. Conditions under which stuttering isreduced or absent: a review of the literature. Jour-nal of Speech and Hearing Disorders, 1949, 14, 295-302.

Ellis, D. S. and Brighouse, G. The effects of music onrespiration and heart-rate. American Journal of Psy-chology, 1952, 65, 39-47.

Flanagan, B., Goldiamond, I., and Azrin, N. Operant

SYNCHRONIZATION APPLIED TO STUTTERING 295

stuttering: the control of stuttering behaviorthrough response-contingent consequences. Journalof the Experimental Analysis of Behavior, 1958, 1,173-177.

Flanagan, B., Goldiamond, I., and Azrin, N. H. In-statement of stuttering in normally fluent individu-als through operant procedures. Science, 1959, 130,979-981.

Fransella, F. Rhythm as a distractor in the modifica-tion of stuttering. Behavior Research and Therapy,1967, 5, 253-255.

Fransella, F. and Beech, H. R. An experimental analy-sis of the effect of rhythm on the speech of stutter-ers. Behavior Research and Therapy, 1965, 3, 195-201.

Freeburne, C. M. and Fleischer, M. S. The effect ofmusic distraction upon reading rate and compre-hension. Journal of Educational Psychology, 1952,43, 101-109.

Freund, H. Psychopathology and the problems ofstuttering. Springfield: Chas. C Thomas, 1966.

Goertzel, V., May, P. R. A., Salkin, J., and Schoop, T.Body-ego technique: an approach to the schizo-phrenic patient. Journal of Nervous and MentalDisease, 1965, 41, 53-60.

Goldiamond, I. Stuttering and fluency as manipulat-able operant response classes. In L. Krasner andL. P. Ullmann (Eds.), Research in behavior modifi-cation. New York: Holt, Rinehart & Winston, 1965.

Hejna, R. T. Speech disorders and nondirective ther-apy. New York: Ronald Press Co., 1960.

Knudson, V. 0. Hearing with the sense of touch.Journal of General Psychology, 1928, 1, 320-352.

Martin, R. R. and Siegel, G. M. The effects of re-sponse-contingent shock on stuttering. Journal ofSpeech and Hearing Research, 1966, 9, 340-352. (a)

Martin, R. R. and Siegel, G. M. The effects of simul-taneously punishing stuttering and rewarding flu-ency. Journal of Speech and Hearing Research, 1966,9, 466-475. (b)

Meyer, V. and Mair, J. M. M. A new technique to

control stammering: a preliminary report. BehaviorResearch and Therapy, 1963, 1, 251-254.

Murphy, A. T. and Fitzsimons, R. M. Stuttering andpersonality dynamics. New York: Ronald Press Co.,1960.

Newman, R. I., Hunt, D. L., and Rhodes, F. Effectsof music on employee attitude and productivity ina skateboard factory. Journal of Applied Psychol-ogy, 1966, 50, 493-496.

Quist, R. W. and Martin, R. R. The effect of responsecontingent verbal punishment on stuttering. Jour-nal of Speech and Hearing Research, 1967, 10, 795-800.

Rieber, R. W. and Brubaker, R. S. Speech pathology.Amsterdam: North-Holland Pub. Co., 1966.

Siegel, S. Nonparametric statistics. New York: Mc-Graw-Hill, 1956.

Siegel, G. M. and Martin, R. R. Experimental modifi-cation of disfluency in normal speakers. Journal ofSpeech and Hearing Research, 1965, 8, 235-244. (a)

Siegel, G. M. and Martin, R. R. Verbal punishmentof disfluencies in normal speakers. Journal of Speechand Hearing Research, 1965, 8, 246-251. (b)

Smith, P. C. and Curnow, R. "Arousal hypothesis"and the effects of music on purchasing behavior.Journal of Applied Psychology, 1966, 50, 255-256.

Travis, R. E. Handbook of speech and pathology. NewYork: Appleton-Century-Crofts, 1957.

Trotter, W. D. and Lesch, M. M. Personal experienceswith a stutter-aid. Journal of Speech and HearingDisorders, 1966, 32, 270-272.

Uhrbrock, R. S. Music on the job: its influence onworker morale and production. Personnel Psychol-ogy, 1961, 14, 9-38.

Zimney, G. H. and Weidenfeller, E. W. Effects ofmusic upon GSR of children. Child Development,1962, 33, 891-896.

Zimney, G. H. and Weidenfeller, E. W. Effects ofmusic upon GSR and heart-rate. American Journalof Psychology, 1963, 76, 311-314.

Received 1 October 1968.