Single-Case Designs and Clinical Biofeedback Experimentation

Transcription

1 Bofeedback and Self-Regulaton, VoL 2, No. 3, 1977 Sngle-Case Desgns and Clncal Bofeedback Expermentaton Davd H. Barow: Brown Unversty and Butler Hosptal Edward B. Blanchard Unversty of Tennessee Medcal School Steven C. Hayes Brown Unversty and Butler HosptaP Leonard H. Epsten Auburn Unversty Rgorous evaluaton of the effects of bofeedback wth clncal populatons s necessary, but practcal problems often preclude utlzaton of betweengroups expermental desgns nvolvng large numbers of clents wth clncally relevant problems. Sngle-case expermental desgns provde a vable alternatve for answerng most research questons. n addton, sngle-case desgns possess several dstnct advantages for bofeedback research, ncludng a focus on clncal sgnfcance, the use of varablty as data not error, unque procedures for establshng generalty of fndngs, and an ablty to deal wth ethcal concerns n clncal research. Basc procedures n the use of sngle-case expermental desgns are descrbed and llustratons n clncal bofeedback research are provded. t has been the hstory of the development of new therapeutc procedures n psychology and psychatry that early descrptons are founded upon observaton, speculaton, and unsystematc evaluaton. Gradually, as these developments become mature, more sophstcated evaluaton s demanded and the scentfc method s brought to bear on the major assumptons of the procedures. The feld of clncal bofeedback s no excepton. Although some results of clncally relevant bofeedback have been reported n a number of meetngs, artcles, and books, and although bofeedback has 'Address all correspondence to Dr. Davd H. Barlow, Department of Psychatry, Butler Hosptal, 345 Blackstone Boulevard, Provdence, Rhode sland Now at Unversty of North Carolna at Greensboro. 221 Ths journal s copyrghtecl by Plenum. Each artcle s avalaple for $7.50 from Plenum Publshng Corporaton, 227 West 17th Street, New York, N.Y

2 222 Badow et a. receved a great deal of publcty n the popular press, most of the early work n ths area has faled to meet the standard "rules of evdence" n our dscplnes. But bofeedback should be evaluated on the same bass as one would evaluate any other therapeutc procedure, as noted recently by Blanchard and Young (1974), among others. Ths evaluaton wll requre the rgorous use of expermental desgns approprate to the evaluaton of clncal applcatons of bofeedback. The most usual expermental methods brought to bear on clncal problems s the between-groups comparson desgn. Unfortunately, n the area of clncal bofeedback, as n psychotherapy research n general, a major stumblng block has been the dffculty n accumulatng the large numbers of reasonably homogeneous subjects from clncal populatons necessary to execute a proper study (Bergn & Strupp, 1970; Hersen & Barlow, 1976). Whether one s dealng wth mgrane headache or premature ventrcular contractons, only n major teachng hosptals s the clncal researcher lkely to gather suffcent patents to detect the effects of a bofeedback procedure that supercedes the large ntersubject varablty found n clncal populatons. Perhaps for ths reason only 4 of the 26 studes descrbed n Blanchard and Young's (1974) revew of clncal applcatons of bofeedback utlzed a between-groups expermental desgn to evaluate a bofeedback procedure. Of these, one study used speech-phobc and another test-anxous subjects, populatons commonly employed n analogue psychotherapy research because of ready avalablty of subjects n college settngs. An alternatve approach, frmly grounded n the scentfc method and meetng commonly accepted rules of evdence n our scence, s the use of sngle-case expermental desgns (Barlow & Hersen, 1973; Letenberg, 1973; Hersen & Barlow, 1976). Sngle-case desgns have already begun to appear n the bofeedback lterature. Of the 22 remanng studes n the Blanchard and Young revew, 5 utlzed desgns enablng a reasonably clear evaluaton of the effects of bofeedback. The remanng studes conssted mostly of anecdotal case studes, whch should not be confused wth sngle case research. The purpose of ths paper s to examne the ratonale behnd the use of sngle-case desgns to llustrate the actual and potental applcaton of snglecase desgns to bofeedback expermentaton wth clncal populatons. ADVANTAGES OF THE SNGLE-CASE APPROACH The sngle-case desgn has roots deep n the hstory of psychology and physology (Hersen & Barlow, 1976) and possesses several dstnct features that make t partcularly approprate for clncal research.

3 Sngle-Case Desgns and Bofeedback Expermentaton 223 Clncal versus Statstcal Sgnfcance Due to the manner n whch data are presented, sngle-case desgns hghlght clncal rather than statstcal sgnfcance. Snce group expermental desgns all but requre the use of statstcal procedures n order to assess treatment effects, the defnton of a meanngful change n group desgn s often statstcal. Statstcal sgnfcance, however, can easly occur when the dfferences between groups are very small. For example, a study demonstratng that heart rate can be decreased relably by one or two beats per mnute wll not excte much nterest n clncans nterested n tachycarda. Nevertheless, f ths dfference s a relable one, t s lkely to be statstcally sgnfcant, thereby suggestng that an effectve "treatment" has been dscovered. Sngle-case desgns, on the other hand, present repeated measures for each ndvdual so that the magntude of change s readly apparent. n most cases, changes are large enough to be obvous by vsual nspecton (nonoverlappng dstrbutons), although statstcal procedures are avalable f needed (Kazdn, 1976). The Use of Varablty as Data, Not as Error The manner n whch varablty s handled n sngle-case desgns underlnes the mportance placed on the ndvdual n sngle case research. Repeated measurement of physologcal processes n a sngle case approach hghlghts ntrasubject varablty (whch becomes ntersubject varablty n the context of a large group). For example, blood pressure measurements n a hypertensve patent may show cyclcal varablty when repeatedly measured. Further nvestgaton may reveal ncreased blood pressure assocated wth certan work experences such as an mportant busness meetng occurrng every 2 weeks. One mght then alter the expermental desgn to test the relatonshp of the busness meetng to blood pressure and ultmately ntate clncal bofeedback tranng, takng ths nformaton nto consderaton. Most between-groups desgns, on the other hand, would measure changes only after tranng (from pretest to posttest). The ndvdual descrbed above mght be posttested j~t before hs busness meetng. Ths varablty now becomes "ntersubject" varablty after averagng the data from all ndvduals n the expermental group and s usually referred to as error. Often the error s consdered ntrnsc to the response beng measured rather than due to lawful relatonshps among the physologcal response and other events. n the sngle-case approach, sources of varablty are traced down through the use of "mprovsed and rapdly changng desgns" (Sknner, 1966), allowng greater specfcty of the factors controllng a physologcal response n a gven ndvdual.

4 224 Barow e( al. Generalzng from a Sngle Case One of the apparent shortcomngs of sngle-case research s that one does not know f the results from a partcular case would be relevant to another case. Even f one has carefully solated the actve ngredents for a partcular treatment usng sngle-case methodology, one does not know whether or not the effects obtaned wll generalze across other clents wth the sample problem, or dfferent physologcal responses n the same clent. Smlarly, one does not know f the same effect would obtan wth dfferent therapsts (or perhaps dfferent equpment) or n dfferent settngs such as laboratory versus natural envronment. Ths ssue has often been an nhbtng factor n the applcaton of sngle-case methodology (Kesler, 1971). But wthn the sngle-case approach one establshes generalty of fndngs by careful replcaton procedures on addtonal ndvduals. At least three types of replcaton procedures for appled clncal settngs and drect, clncal, and systematc replcaton have been descrbed recently (Hersen & Barlow, 1976). Snce the fact remans that treatments n clncal settngs are constructed ultmately for the ndvdual rather than the nonexstent "average" person n a group, replcaton of procedures on addtonal ndvduals takes on added mportance. The advantages and dsadvantages of establshng generalty of fndngs usng sngle-case methodology or between-groups methodology has been descrbed n some detal elsewhere (Hersen & Barlow, 1976). Ethcal Consderatons As clncal evdence accumulates on the effectveness of bofeedback, human subjects commttees are less lkely to allow the use of no treatment control groups despte the seemng llogc of ths poston,.e., one would not bother to evaluate the treatment f one knew t worked. n the frst author's recent experence, a polcy settng group was reluctant to allow the use of no-treatment controls n an evaluaton of bofeedback on premature ventrcular contractons (PVCs) on the premse that ths s a very serous condton and Wess and Engel's (1971) early seres of uncontrolled case studes seemed to demonstrate that bofeedback was effectve. Snce subjects serve as ther own control n sngle-case desgns, all subjects receve whatever clncal beneft s obtanable. GENERAL PROCEDURES N SNGLE-CASE RESEARCH Ths secton wll brefly outlne some of the basc procedures fundamental to all sngle-case expermental desgns.

5 Sngle-Case Desgns and Bofeedback Expermentaton 225 Repeated Measurement Sngle-case approaches requre repeated measurement of the specfc domans of nterest, whether they be physologcal, behavoral, or cogntve. n fact, the mportance of repeated measurement to sngle-case research s underlned by the fact that some authors (Brownng & Stover, 1971) have stated that t alone s suffcent to upgrade a smple anecdotal case study of the type typcally assocated wth early psychatrc and psychologcal treatment to a quas-expermental desgn. Repeated measurement, of course, s crucal to the examnaton of varablty. deally, measurement should be made both n treatment sessons and at separate measurement (generalzaton) sessons. n bofeedback research one can have the followng stuatons: 1. The response of clncal nterest s the response for whch feedback s gven and whch s recorded durng the normal course of treatment. An example would be blood pressure n hypertenson or heart rate n treatment of tachycarda. n such a case one could obtan reasonable treatment outcome data durng treatment sessons. However, a better condton would be to add a "self-control" or "no feedback" phase just before each sesson. One could also have separate measurement or "no feedback" generalzaton sessons. 2.The response of clncal nterest s routnely recorded durng treatment sessons but feedback s gven for a dfferent response. An example would be treatment of PVCs (Wess & Engel, 1971) by tranng n control of heart rate. A second example would be use of frontals EMG feedback (for relaxaton) to treat elevated blood pressure n hypertensves. n ths case one needs repeated measurement of both responses. Moreover, change n the clncal response should concde wth change n the response for whch feedback s gven to be meanngful. One could stll admnster "no feedback" phases just before each sesson or separate generalzaton phases, at least for the response of clncal nterest. 3. The response of clncal nterest s prmarly a self-report, whle feedback s gven for a dfferent response. An example would be treatment of tenson headaches by frontals EMG feedback (Budzynsk, Stoyva, & Adler, 1970)or treatment of mgrane headache by thermal (fngertp temperature) feedback (Sargent, Green, & Waters, 1972). n ths case, self-report data on the clncal response are routnely beng gathered separately from the treatment sessons. However', one s nterested n seeng f the clncal response of nterest (headache ntensty or duraton) changes concdent wth changes n the response for whch feedback s gven. Ths s partcularly crtcal n lght of Epsten and Abel's (n press) data on EMG feedback and tenson headaches demonstratng that EMG may change wthout mprovement n headaches and mprovement n headaches may occur

6 226 Barlow et a. wthout any apparent learnng of EMG control. Here agan, one may want repeated separate measurement sessons to see how much self-control or no feedback control the patent had acqured. Baselne Phase Most sngle case desgns nclude an ntal perod of observaton wth no expermental manpulatons. n ths phase the subject's performance s measured under no feedback condtons untl a suffcent degree of stablty s obtaned (Hersen & Barlow, 1976). The defnton of a stable baselne pattern s a dffcult one and has been a matter of some dscusson (Sdman, 1960; Barlow & Hersen, 1973). At a mnmum, three separate observaton ponts are requred to establsh a trend n the data (Hersen & Barlow, 1976). The partcular trend that s obtaned may be of several types. The most desrable trend s one n whch there s a steady rate of physologcal respondng wth only mnor varatons upward or downward from the average value for the phase. A second trend, whch s also acceptable n appled clncal work, s one n whch the behavor s worsenng n a steady manner. For example, n a hypertensve clent blood pressure values may be slowly but steadly rsng. Wth such a deteroratng baselne, any therapeutc effects acheved can be unambguously assessed. Baselne patterns that are most troublesome, however, are those n whch there s an mprovement n the behavor of nterest or n whch there s a great deal of varablty wthn the baselne phase. n the frst case, the recommended strategy s to contnue the baselne perod untl a steady pattern emerges or untl the need for clncal nterventon s allevated (Hersen & Barlow, 1976). n the second case, two alternatves are open: ether the source of the varablty can be explored and brought under expermental control so as to acheve a more stable baselne or the baselne can be contnued wth the hope that some knd of stablty, n an acceptable range, wll be acheved, usually through adaptaton to the measurement stuaton (Hersen & Barlow, 1976). Knowledge of typcal varablty n the response beng measured s also useful n determnng length of baselne. Changng One Varable at a Tme Another mportant general procedure n sngle-case expermental desgns s to change only one varable at a tme. Ths s a rule that has often been volated n sngle-case research (see Hersen & Barlow, 1976, for a more detaled dscusson). There are exceptons to ths rule, but n general the sngle-case researcher should adhere to ths tactc. n part ths s dctated by

7 Sngle-Case Desgns and Bofeedback Expermentaton 227 the fact that the major ncrement n scentfcally useful evdence occurs durng phase changes. f two or more varables are altered at one tme, t s mpossble to say whch varable s responsble for any change. For example, f one wshes to add a renforcng consequence to bofeedback, the desgn would proceed as follows: A (baselne), B (bofeedback), BC (bofeedback and renforcement), wth a return to B and BC. An A-BC-A-C desgn, for example, would produce unnterpretable data. Even an A-B-C-B desgn would be dffcult to nterpret snce the change from the B phase to the C phase would nvolve the smultaneous removal of bofeedback and ntroducton of renforcement. Unform Length of Phases Fnally, general procedures n sngle-case research call for the use of phases of smlar length. Ths s a pont that s often gnored n sngle-case expermental work and only recently has been developed n some detal (Hersen & Barlow, 1976). The need for expermental and baselne phases of smlar lengths s due to the fact that data are often cyclcal n nature and the use of phases of wdely dvergent lengths wll often dsguse ths cyclcal varablty leadng to mstaken nterpretaton of data. Control Procedures The purpose of any experment s to determne the effect of the ndependent varable or treatment n queston over and above other factors that may also affect the dependent varable. Naturally the specfc control procedures wll depend on the specfc bofeedback procedure beng tested and the nature of the target physologcal system. For example, the treatment of mgrane headache through bofeedback of the handwarmng response has some clncal support (Sargent et al., 1972; Turn & Johnson, 1976). One possble control for the effects of bofeedback per se would be warmng the hands through mmerson n warm water. An obvous control procedure for EMG feedback s muscle relaxaton procedures. However, the new specfcty of these relaxaton procedures should allow control phases n whch more specfc muscles are relaxed, provdng a more sutable control procedure for bofeedback of a specfc muscle group than the more general relaxaton procedures n common use (Wolfe, 1976). Whatever the specfc response, recent evdence ndcates that the most mportant control procedure s one n whch the subject fully expects that the change wll occur wthout a specfc bofeedback procedure. Whether nstructons, placebo treatments, noncontngent bofeedback, or a combna-

8 228 Barow et al. ton of these procedures s used, the effects of bofeedback must be apparent over and above any effects from ths type of control procedure to convnce the scentfc world that the bofeedback phenomenon exsts. The next secton wll llustrate how ths control procedure can be ncorporated nto sngle-case desgns. TYPES OF SNGLE-CASE DESGNS Case Reports The sngle-case expermental desgn should not be confused wth anecdotal case reports. Case report s a term that apples when there has been lttle systematc data collecton, partcularly f the baselne condton before therapeutc nterventon s descrbed n anecdotal fashon. Any changes found n anecdotal case reports can, of course, serve for the generaton of scentfc hypotheses. However, they cannot generate scentfcally vald evdence snce the conclusons reached could very easly be the result of confoundng varables n the patent's lfe and because the nature of the change s often one that s not well specfed or measured n a relable fashon. A-B Desgn The A-B sngle-case paradgm s probably the most frequently used tactc n sngle-case approaches. n the A-B desgn the clent's behavor n baselne s repeatedly assessed untl stablty s obtaned, the therapeutc nterventon s made, and assessment of the clent's behavor contnues. t represents a clear mprovement over the anecdotal case report nasmuch as any changes obtaned from the A to B phase can be clearly specfed. However, t shares a major defcency wth the anecdotal or uncontrolled case study snce change from A to B phases could easly be accounted for by confoundng varables n the patent's lfe. For that reason, the A-B desgn has been termed a systematc case study (Blanchard, Note 1) and a quasexpermental desgn (Campbell & Stanley, 1966). A good example of an A-B desgn n bofeedback research s the study reported by Mller (1972). n ths study a female hypertensve patent was run for 26 baselne trals before beng taught n 58 subsequent trals to control blood pressure usng bnary, audtory feedback on a beat-to-beat bass. The results of ths nterventon ndcated that the patent could relably decrease her dastolc blood pressure from 97 mm Hg to 76 mm Fg, but no expermental analyss was performed (see Fgure 1).

9 Sngle-Case Desgns and Bofeedback Expermentaton 229 ZO F~ 8. Slort lronntj O0 ~ 90 ~~97 f~ ~ ~,,~ Oschorqe from hosptal r f / Ourele wlhdrown 6 80 g t t~ldometwthdrewn250 mq t..d. t V ~*r~'~76 beqn L- clopa stop L- dopo to ~dul. Aug. Sep, : Oef.~ Fg. 1. General reducton n dastolc blood pressure concurrent wth learnng of voluntary control. The horzontal lne at the upper left represents the average blood pressure whle the patent was n the hosptal pror to tranng and on the anthypertensve drugs ndcated. The horzontal lne at the lower rght represents the average blood pressure durng 30 days wthout drugs and n a more stressful lvng stuaton outsde of the hosptal. (Reprnted from Mller, N. E. Postscrpt. n D. Sngh and C. T. Morgan [Eds.], Current status of physologcal psychology: Rea~'ngs. Brooks/Cole, Monterey, Calforna, 1972.) A-B-A Desgn n the A-B-A desgn, the clent's behavor s repeatedly assessed n baselne, treatment, and baselne phases. f, after baselne measurement "A," the applcaton of the therapeutc procedure "B" and ts subsequent removal "A" s assocated wth an mprovement whle the treatment s n effect and a subsequent deteroraton when treatment s wthdrawn, then one can make a reasonable concluson that the treatment s responsble for change. An example of ths desgn n the bofeedback lterature s a study by Blanchard, Young, and Haynes (1975) on the treatment of hypertenson n whch the data n Fgure 2 were reported but not llustrated. n ths case feedback produced a clear drop of approxmately 20 mm n systolc pressure from baselne levels. Two data ponts obtaned n the second baselne phase ndcate an ncrease n both level and slope over the feedback phase, but at least two more ponts would make these data more convncng. The major problem wth the A-B-A desgn n appled clncal work s not ts usefulness n generatng scentfcally valuable nformaton but the

10 230 Barow et al O~..J~ o < 150- "~ 14o Basel ne E ' ~o,! Feedback g, SESSONS! Baselne 1 b 1'1 Fg. 2. Effects of feedback on systolc blood pressure n an A-B-A desgn. dffculty nherent n concludng an experment wth a baselne phase f some mprovement had occurred durng the prevous treatment phase. Ths concern has led to the greater use of the next desgn. A-B-A-B Desgn n the A-B-A-B desgn, the treatment s rentroduced after havng once been wthdrawn. Ths s a stronger desgn than the A-B-A desgn nasmuch as the effects of rentroducng the ndependent varable can be assessed for a second tme. n addton, t s a desgn that s more generally approprate for clncal use snce the desgn ends wth the nterventon n place. There are several good examples of A-B-A-B desgns n the bofeedback lterature. These nclude studes by Sterman (1973), Epsten, Hersen, and Hemphll (1974), Lubar and Bahler (1976), and Blanchard et al. (1975). To llustrate the A-B-A-B desgn, addtonal data reported but not publshed n the Blanchard et al. (1975) study are presented (Fgure 3). Once agan, feedback produces a large drop n blood pressure over baselne. n the second baselne phase blood pressure rses well above the last three ponts n feedback and then drops once agan to new lows when feedback s rentroduced. One dffculty detractng from the confdence wth

11 Sngle-Case Desgns and Bofeedback Expermentaton 231 q~ 190~ 180 ~ 170 tj E B~sellne Feedback! ~'.~llne (Feedback) j s 1 1 ~ f! 1! toll~,v.,up o SESSONS Fg. 3. Effects of feedback on systolc blood pressure n an A-B-A-B desgn. whch one can draw postve conclusons about bofeedback n ths experment s a volaton of the "unform length of phase" gudelne. Although both baselne phases consst of four data ponts, the frst feedback phase conssts of nne ponts. Based on the frst four data ponts of the feedback phase, one could not conclude that feedback was effectve. n a very conservatve fashon, one mght also say that drops mght be due to smple accommodaton to a phase and that blood pressure would have dropped f the frst baselne phase conssted of nne ponts. Whle the mmedate mprovement n the last feedback phase makes ths very doubtful, the data would be more convncng f the frst baselne phase conssted of approxmately nne ponts. However, one must always balance ths gudelne aganst the flexblty of extendng a phase f a promsng trend appears. An extenson of the A-B-A-B desgn partcularly approprate for bofeedback research would be the A-B-BC-B-BC desgn, where B s an nstructonal placebo dscussed n the secton on control phases and C s the bofeedback procedures under examnaton. Ths desgn allows one to solate the effects of bofeedback over and above the effects of the placebo. Unfortunately, t has not been used n any reported clncal bofeedback research to the best of our knowledge.

12 232 Barlow et a. nteracton Desgns n addton to the relatvely straghtforward wthdrawal desgns, descrbed above, sngle-case expermental desgns can also be used to assess the relatve or combned effects of specfc components of therapeutc nterventons. Whle there are no examples of such studes as yet n the bofeedback lterature, they may well be utlzed to answer certan types of questons n the area. Brefly, some examples of nteracton desgns would be as follows: n an A-BC-B-BC desgn, a treatment package that ncludes more than one varable s mplemented and then one of these varables s removed and re-ntroduced. For example, a study that wshed to determne the separate and combned effect of dfferent forms of feedback mght employ ths desgn, n whch the subject receves two forms of feedback (B and C). One form of feedback ((2) s then removed and rentroduced. Ths allows a far assessment of the addtve effects of a specfc component of the treatment package (C). ts weakness s that t does not gve a very clear assessment of the varable that s left n place throughout the fnal three phases of the experment, namely, the B varable. One way to solve ths s to go to a more complex desgn such as the A-B-A-B-BC-B-BC desgn, whch allows for the separate determnaton of the effectveness of the B varable and the addtve effect of the C varable. f one wshed to then determne the sngle effect of the C varable and the combned or addtve effect of the B varable, one could attempt an A-C-A-C-BC-C-BC desgn on subsequent subjects. A number of more complcated varants on the nteracton desgn are avalable. The nterested reader s referred to Hersen and Barlow (1976). One common factor n all of the above desgns s that a clear assessment of the effects of the ndependent varable requres a degree of reversblty n the performance. f, for example, a specfc behavor, once learned, would not return to baselne, these desgns would be napproprate for determnng the effects of these varables. Whle several researchers (e.g., Sterman & Frar, 1972; Sterman, 1973) have produced data showng that the results of bofeedback are often reversble, other expermenters (e.g., Blanchard & Scott, 1974; Blanchard & Abel, 1976) have reported that t s often dffcult to acheve reversals n bofeedback research. Two optons are avalable. One s to allow the treatment varables to be n effect for a short perod of tme (Hersen & Barlow, 1976). Such a strategy often produces effects that are more easly reversed wth other target behavors (e.g., Agras, Barlow, Chapn, Abel, & Letenberg, 1974) and t s possble ths mght be an effectve strategy n bofeedback research. Alternatvely, several expermental desgns that do not nvolve reversals are avalable.

13 Sngle-Case Desgns and Bofeedback Expermentaton 233 The Multple-Baselne Desgn The multple-baselne desgn was frst fully descrbed by Baer, Wolf, and Rsley (1968). Essentally, t conssts of a seres of separate A-B desgns n whch the length of the baselne perod s vared n order to avod the lkelhood of a correlaton between other events and the ntroducton of the ndependent varable. There are bascally three types of multple-baselne desgns. n the frst type, a multple baselne across behavors, the ndependent varable s appled sequentally to separate and, deally, ndependent target behavors wthn a sngle subject. A second type of multple-baselne desgn s the multple baselne across settngs n whch a specfc ndependent varable s appled sequentally to a sngle subject for a sngle behavor, but n dfferent settngs or stuatons. The thrd type s the multple-baselne desgn across subjects n whch the ndependent varable s sequentlly appled to dfferent subjects for the same problem behavor. For example, the length of baselne for the frst subject mght be 1 week; for the second subject, 2 weeks, etc. Multple-baselne desgns hold out certan clear advantages to the expermenter, especally n an appled settng. Frst, snce the only two condtons are baselne and treatment, wth varaton only n the number and/or length of baselnes, the desgn s partcularly useful when a treatment cannot be wthdrawn due to ethcal consderatons. Second, as mentoned above, the desgn does not requre reversblty n the data. One of the major ssues n the use of multple-baselne desgns, regardless of the specfc type, s the number of baselnes that are requred n order for scentfcally vald data to be generated. Ths s a matter of some dscusson (Hersen & Barlow, 1976; Baer et al., 1968; Wolf & Rsley, 1971). Although there are no hard and fast rules n the area, t seems that, at a mnmum, three to four baselnes would be requred to generate convncng effects wth multple-baselne desgns (Hersen & Barlow, 1976). There have been only a few reports of the use of multple-baselne desgns n bofeedback research (e.g., Drury, DeRs, & Lberman, Note 2; Beatly, Note 3). However, t would seem that current questons n bofeedback expermentaton could well be addressed wth these desgns. For example, n the clncal settng, persons wth multple dffcultes or persons wth sngle dffcultes that relate to multple behavors could be treated through the sequental treatment of specfc behavors, physologcal or otherwse. n the use of EMG feedback for muscular reeducaton wth stroke patents, one mght obtan baselne measures on each muscle group but apply EMG feedback to one specfc muscle group at a tme. The multple-baselne across settngs desgn may be of clncal use where a relevant

14 234 Badow et al. 90 N~L.... ~.S. E.. ~ :... o. ~ 95 ae 9O gs 80- / 75 t MNUTES Fg. 4. The effects of temperature bofeedback on fngertp skn temperature n a multple baselne across three subjects.

15 Sngle-Case Desgns and Bofeedback Expermentaton 235 response s attached to several specfc stmul or stuatons. For example, Blanchard and Abel (1976) treated an ndvdual wth a rape-nduced psychophysologcal cardovascular dsorder. Ths dffculty seemed to occur n several dfferent and specfc envronmental stuatons nvolvng dfferent sexually related cues. Whle obtanng baselne measures of heart rate n each stuaton, t may have been possble to tran the ndvdual n control of heart rate, frst n one specfc sexual scene or stuaton and then n the second, and so on. n the Blanchard and Abel (1976) report, however, the effects of bofeedback generalzed across scenes and stuatons n that tranng for one "scene" produced wdespread mprovement n all problem stuatons. Such a generalzaton s one of the potental dffcultes wth multple-baselne desgns snce an ndependence among the specfc baselnes s requred to establsh causal relatonshp. The thrd multple-baselne desgn, multple baselne across subjects, seems to be a partcularly approprate one for bofeedback tranng (Blanchard, Note 1). The key element n ths desgn, whch dstngushes t from multple systematc case studes, s that the baselne condtons are of varyng lengths across subjects and the treatment s ntroduced sequentally after longer and longer baselne phases. f a change n the target response s consstently correlated wth an ntroducton of the ndependent varable, then one can say, wth a good deal of certanty, that t s the ndependent varable and not merely the passage of tme, the measurement operaton, or some ndependent event n the subject's lfe that s causng the observed change. An example of ths desgn comes from Drury et al. (Note 2), who treated mgrane headache wth thermal feedback. One porton of ther data presents fngertp skn temperatures for ther subjects wth feedback ntroduced after dfferent tme ntervals for each subject. Clear changes n temperature occurred only when tranng was ntroduced (at the dotted lne), suggestng a causal relatonshp between the feedback package and fngertp temperatures. Fgure 4 also llustrates the most usual method of presentng multple-baselne data, whether across behavors, stuatons, or subjects. Two addtonal desgns are relevant when behavor s not deemed reversble and yet the number of behavors, settngs, or subjects necessary for a multple-baselne desgn s not avalable. One desgn s termed the multple-schedule or multelement baselne desgn (Hersen & Barlow, 1976; Ullman & Sulzer-Azaroff, 1975; Letenberg, 1973). The second s termed the changng crteron desgn. To the best of our knowledge nether desgn has appeared n the bofeedback lterature. Multple-Schedule Desgn n the frst desgn the potental exsts to compare the effects of two treatments wthn the same ndvdual on the same problem. For example, f

16 236 Barlow et al. one wshed to compare the effects of two varetes of EMG feedback on frontals muscle actvty, these treatments could be compared n a multpleschedule desgn by assocatng each treatment wth a dfferent stmulus (two colored lghts, to take a smple example, or perhaps two dfferent expermenters). The two treatments could each be presented once each day or perhaps on alternate days, and reducton n frontals muscle actvty durng each treatment would be plotted separately as treatment progressed, but n the same fgure so that ready comparson of relatve progress would be observable. The noton here s that the subject learns the dscrmnaton between treatments, whch reduces sequental confoundng to some extent and permts the relatve effects of the two treatments to become apparent. n another varaton of the desgn, treatment could be compared to no treatment wthout wthdrawng treatment for any length of tme by, once agan, rapdly alternatng treatment and no treatment and assocatng each wth dfferent stmul (e.g., Agras, Letenberg, Barlow, & Thomson, 1969). Whle some carry-over of treatment effects may occur from one sesson to the next (sequental confoundng), typcally a good dscrmnaton s eventually formed allowng assessment of the relatve effects of treatment. Ths desgn has been used successfully n evaluatng procedures other than bofeedback (Hersen & Barlow, 1976) and consultaton of ths reference or other references noted above s recommended for addtonal detals on mplementaton and presentaton of data. Changng-Crteron Desgn The changng-crteron desgn (Axelrod, Hall, Wes, & Rohrer, 1974; Hartmann & Hall, n press) may be approprate for evaluatng some forms of bofeedback tranng. Bascally, baselne data are collected on one specfc behavor and crtera are set for desred changes wthn a specfc perod of tme. For example, the crteron set for a tachycarda patent may be a lowerng of fve beats per mnute every thrd sesson, and the tranng sesson s set up specfcally to acheve ths goal. The crtera may be altered to 2 BPM or 10 BPM n subsequent weeks. To the extent that the patent meets the crtera, partcularly f the crteron s changed from tme to tme, one can assume a causal relatonshp. f, however, large drops n heart rate occur over and above the crteron, or f the correlaton between the crteron and actual changes s otherwse poor, then other factors are most lkely contrbutng to change. The desgn s not as powerful as some unless the ft between the crteron and behavor s very good. t s also helpful f the crteron s varable (wthn a reasonable range) and the tme between tranng sessons s varable, to rule out temporal factors assocated wth change. As Hartmann

17 Sngle-Case Desgns and Bofeedback Expermentaton 237 and Hall (n press) note, ths desgn s most useful n stuatons where the response can be modfed n a stepwse fashon and where the changes occur reasonably promptly and stablty at the next level s acheved. f these factors obtan, the changng-crteron desgn s potentally useful n bofeedback research. DSCUSSON t would seem that sngle-subject desgns are approprate to all areas of clncal bofeedback research. The frst step, already well under way, s to demonstrate that bofeedback procedures produce large, clncally relevant effects. A second step s to determne the effects of the bofeedback package over and above a strong demand or placebo condton. Assumng postve results from ths ntal step, a thrd step s to pck apart the feedback package to determne the actve ngredents. One may then dscard the nactve ngredents, bolster the actve ngredents, and develop a more effectve treatment package. Presumably at the same tme, between-groups factoral experments wth readly avalable nonclncal populatons, usually on college campuses, wll be ongong wth smlar goals. Some of ths work wll undoubtedly be relevant to clncal populatons f t's carefully done, but most of t wll need replcaton n clncal populatons. nvestgators workng wth clncal populatons should be aware of fndngs from analogue studes n order to test out new developments usng sngle-case methodology. Of course, there are several questons that cannot be answered wth sngle-case desgns. The multple-schedule desgn notwthstandng, t s very dffcult to compare the effects of two treatments, both of whch produce some mprovement. To answer ths queston, the between-groups comparson desgn s most useful. A second queston often asked by socety and by the communty of therapsts s the actuaral one on percentages of people lkely to mprove wth a gven treatment. Obvously, a treatment must be appled to large groups to provde ths answer, but both of these questons arse relatvely late n the usual sequence of the development of new therapeutc procedures. Gven the dffculty n accumulatng large numbers of subjects when workng wth clncal populatons, t would be neffcent, at least, for the clncal nvestgator to accumulate groups of subjects to answer questons amenable to sngle-case approaches. Fnally, the sngle-case approach s relatvely easy to utlze n most clncal stuatons. The most dffcult part s usually the development and admnstraton of approprate objectve and repeated measures, and the necessty of obtanng a stable baselne. But the very nature of bofeedback

18 238 Barlow et a. provdes not only the subject but also the expermenter wth an objectve, repeated measure of the physologcal response, somethng that does not exst n other areas of clncal research. Thus, the area of bofeedback should be greatly advanced by the approprate use of sngle-case methodology. REFERENCE NOTES 1. Blanchard, E. B. Expermental desgn consderatons n clncal bofeedback research. Paper presented at the 7th Annual Meetng of the Bofeedback Research Socety, Colorado Sprngs, Colorado, February Drury, R. L., DeRs, W. J., & Lberman, R. P. Temperature bofeedback treatment for mgrane headaches: A controlled study. Unpublshed manuscrpt, Camarllo-Neuropsychatrc nsttute Research Center, Beatly, E. T. Feedback-asssted relaxaton tranng as a treatment for gastrc ulcers. Paper presented at the 7th Annual Meetng of the Bofeedback Research Socety, Colorado Sprngs, Colorado, February REFERENCES Agras, W. S., Barlow, D. H., Chapn, H. N., Abel, Go G., & Letenberg, H. Behavor modfcaton of anorexa nervosa. Archves of General Psychatry, 1974, 30, Agras, W. S., Letenberg, Ho, Barlow, D. H., & Thomson, L. E. nstructons and renforcement n the modfcaton of neurotc behavor. Amercan Journal of Psychatry, 1969, 125, Axelrod, S., Hall, R. V., Wes, L., & Rohrer, S. Use of self-mposed contngences to reduce the frequency of smokng behavor. n M. J. Mahoney & C. E. Thoresen (Eds.), Se/fcontrol: Power to the person. Belmont, Calforna: Brooks/Cole, Baer, D. M., Wolf, M. M., & Rsley, T. R. Some current dmensons of appled behavor analyss. Journal of Appled Behavor Analyss, 1968, 1(1), Bal.w, D. H., & Hersen, M. Sngle case expermental desgns: Uses n appled clncal research. Archves of General Psychatry, 1973, 29, Bergn, A. E., & Strupp, H. H. New drectons n psychotherapy research. Journal of AbnormalPsychology, 1970, 76(1), Blanchard, E. B., & Abel, G. G. An expermental case study of the bofeedback treatment of a rape-nduced psychophysologcal cardovascular dsorder. Behavor Therapy, 1976, 7, Blanchard, E. B., & Scott, R. W. Behavoral tactcs for clncal cardac control. n K. Calhoun, H. E. Adams, & K. M. Mtchell (Eds.), nnovatve treatment methods n psychopathology. New York: Wley, Blanchard, E. B., & Young, L. D. Clncal applcatons of bofeedback tranng: A revew of evdence. Archves of General Psychatry, 1974, 30, Blanchard, E. B., Young, L. D., & Haynes, M. R. A smple feedback system for the treatment of elevated blood pressure. Behavor Therapy, 1975, 6, Brownng, R. M., & Stover, D. O. Behavor modfcaton n chld treatment: An expermental and clncal approach. Chcago and New York: Aldne-Atherton, Budzynsk, T., Stoyva, J. M., & Adler, C. S. Feedback-nduced muscle relaxaton: Applcaton to tenson headaches. Journal of Behavor Therapy and Expermental Psychatry, 1970, 1, Campbell, D. T., & Stanley, J. C. Expermental and quas.expermental desgns for research. Chcago: Rand McNally, 1966.

19 Sngle-Case Desgns and Bofeedback Expermentaton 239 Epsten, L. H., & Abel, G. G. An analyss of bofeedback tranng effects for tenson headache patents. Behavor Therapy, n press. Epsten, L. H., Hersen, M., & Hemphll, D. Musc feedback n the treatment of tenson headache: An expermental case study. Journal of Behavor Therapy and Expermental Psychatry, 1974, 5, Hartmann, D. P., & Hall, R. V. A dscusson of the changng crteron desgn. Journal of Appled Behavor Analyss, n press. Hersen, M., & Barlow, D. H. Sngle case expermental desgns: Strateges for studyng behavor change. New York: Pergamon Press, Kazdn, A. E. Statstcal analyses for sngle-case expermental desgns. n M. Hersen & D. H. Barlow, Sngle case expermental desgns: Strateges for studyng behavor change. New York: Pergamon Press, Kesler, D. J. Expermental desgns n psychotherapy research. n A. E. Bergn & S. L. Garfeld (Eds.), Handbook of psychotherapy and behavor change: An emprcal analyss. New York: Wley, Letenberg, H. The use of sngle-case methodology n psychotherapy research. Journal of Abnormal Psychology, 1973, 82, Lubar, J. L., & Bahler, W. W. Behavoral management of epleptc sezures followng EEG bofeedback tranng of the sensormotor rhythm. Bofeedback and Self-Regulaton, 1976, 1, Mller, N. E. Postcrpt. n D. Sngh & C. T. Morgan (Eds.), Current status of physologcal psychology: Readngs. Monterey, Calforna: Brooks/Cole, Sargent, J. D., Green, E. E., & Waters, E. D. The use of autogenc feedback tranng n a plot study of mgrane and tenson headaches. Headache, 1972, 12, Sdman, M. Tactcs ofscento~c research. New York: Basc Books, Sknner, B. F. Operant behavor. n W. K. Hong (Ed.), Operant behavor: Areas of research and applcaton. New York: Appleton-Century-Crofts, Sterman, M. B. Neurophysologcal and clncal studes of sensormotor EEG bofeedback tranng: Some effects on eplepsy. n L. Brk (Ed.), Bofeedback: Behavoral medcne. New York: Grune & Stratton, Sterman, M. B., & Frar, L. Suppresson of sezures n an epleptc followng sensormotor EEG feedback tranng. Electroencephology and Clncal Neurophysology, 1972, 33, Turn, A., & Johnson, W. G. Bofeedback therapy for mgrane headaches. Archves of General Psychatry, 1976, 33, Ullman, J. D., & Sulzer-Azaroff, B. Multelement baselne desgn n educatonal research. n E. Ramp & G. Semb, Behavor analyss: Areas of research and applcaton. Englewood Clffs, New Jersey: Prentce-Hall, Wess, T., & Engel, B. T. Operant condtonng of heart rate n patents wth premature ventrcular contractons. Psychosomatc Medcne, 1971, 33, Wolf, M. M., & Rsley, T. R. Renforcement: Appled research. n R. Glaser (Ed.), The nature of renforcement. New York: Academc Press, Wolfe, J. L. Revew of The drug-free way to sleep soundly and The drug-free way to stop tenson headaches, by A. A. Lazarus. Behavor Therapy, 1976, 7(3), (Revson receved February 11, 1977)