by Pace et al. (1985). These investigators developed

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1 JOURNAL OF APPLIED BEHAVIOR ANALYSIS NUMBEP. 2 (ummep. 1992) A COMPARISON OF TWO APPROACHES FOR IDENTIFYING REINFORCERS FOR PERSONS WITH SEVERE AND PROFOUND DISABILITIES WAYNE FiHm, CAmLEEN C. PIAZZA, LNNN G. BowMAN, Loui P. HAGOPIAN, JAME C. OWENS, AND IRENE SLEVIN THE KENNEDY INSTITUTE AND JOHNS HOPKINS UNIVERSEIY SCHOOL OF MEDICINE The development of effective training program for peron with profound mental retardation remain one of the greatet challenge for behavior analyt working in the field of developmental diabilitie. One ignificant advancement for thi population ha been the reinforcer aement procedure developed by Pace, Ivancic, Edward, Iwata, and Page (1985), which involve repeatedly preenting a variety of timuli to the client and then meauring approach behavior to differentiate preferred from nonpreferred timuli. One potential limitation of thi procedure i that ome client conitently approach mot or all of the timuli on each preentation, making it difficult to differentiate among thee timuli. In thi tudy, we ued a concurrent operant paradigm to compare the Pace et al. (1985) procedure with a modified procedure wherein client were preented with two timuli imultaneouly and were given acce only to the firt timulu approached. The reult revealed that thi forced-choice timulu preference aement reulted in greater differentiation among timuli and better predicted which timuli would reult in higher level of reponding when preented contingently in a concurrent operant paradigm. DESCRIPTORS: aement, concurrent operant, predictive validity, reinforcer preference, everely mentally retarded The identification of powerful reinforcer can be particularly difficult among client with evere to profound mental retardation (Wacker, Berg, Wiggin, Muldoon, & Cavanaugh, 1985). Although reinforcer urvey ued with higher functioning peron are not applicable to thi population, a number of promiing procedure have recently been reported, induding (a) training individual to activate microwitche to indicate reinforcer preference (Dattilo, 1986; Wacker et al., 1985); (b) extending the Premack Principle, wherein contingent opportunity to exhibit high-probability aberrant behavior (e.g., tereotypie, echolalia) wa compared to contingent preentation of food (Charlop, Kurtz, & Caey, 199); and (c) meauring the relative Thi invetigation wa upported in part by Grant No. MCJ from the Maternal and Child Health Service of the U.S. Department of Health and Human Service. The author wih to thank Suan Lachman, Theodoia Paclawkyj, Kelley Harrion, and Cindy Anderon for their competent work on cae included in thi invetigation. Requet for reprint hould be ent to Wayne Fiher, Severe Behavior Unit, The Kennedy Intitute, 77 N. Broadway, Baltimore, Maryland percentage of approach repone made to a tandardized et of timuli repeatedly preented to the client (Green et al., 1988; Green, Reid, Canipe, & Gardner, 1991; Pace, Ivancic, Edward, Iwata, & Page, 1985; Steege, Wacker, Berg, Cigrand, & Cooper, 1989). Of thee procedure, the mot common method for identifying reinforcer for peron with evere to profound retardation i the procedure developed by Pace et al. (1985). Thee invetigator developed a two-tep proce (henceforth referred to a the Pace procedure) in which client were firt ytematically expoed to 16 timuli while oberver meaured whether the client approached each timulu. In the econd tep, the procedure wa validated by demontrating that thoe timuli frequently approached were more potent reinforcer than timuli not frequently approached. Thi procedure ha been found to be uperior to caregiver opinion in identifying reinforcer (Green et al., 1988, 1991) and i ueful in the development of treatment package for maladaptive behavior (Maon, McGee, Farmer- Dougan, & Riley, 1989; Steege et al., 1989). However, Green et al. (1988, 1991) alo reported

2 492 WAYNE FISHER et al. that not all timuli identified a preferred were equally effective a reinforcer. Therefore, it may be ueful to develop an extenion of the Pace procedure that ha greater electivity in differentiating between preferred and nonpreferred timuli. Maon et al. (1989) applied the Pace procedure in combination with an abbreviated timulu-preference aement completed daily to provide an ongoing method of identifying reinforcer. In thi mini-aement, the timuli were preented two at a time, and the children were intructed to pick jut one. Thi forced-choice preentation format may better differentiate preferred from nonpreferred timuli than the Pace procedure becaue it more doely approximate natural ituation in which an individual chooe between potentially available timuli through differential reponding. In baic operant experiment, a concurrent operant paradigm ha been ued to examine choice or preference (Catania, 1963, 1966; Herrntein, 197). With thi paradigm, two or more conequence are imultaneouly available to the ubject and are aociated with different repone (e.g., for a pigeon, pecking could be reinforced on a variableinterval 3- chedule for Key A and on a variableinterval 2- chedule on Key B). Under uch a paradigm, the rate or duration of each repone will generally be proportional to the rate or magnitude of reinforcement aociated with that repone, thu providing a mean for aeing relative preference for variou timuli or chedule (Catania, 1963, 1966). In the example above, the pigeon could receive two reinforcer per minute on Key A and three per minute on Key B; thu, 4% of repone would occur on Key A and 6% on Key B. In the current invetigation, a concurrent operant paradigm wa ued to help determine whether the forced-choice method of timulu preentation decribed above might be a ueful extenion of the Pace procedure. Specific prediction were that (a) ignificantly more timuli would be identified a highly preferred through the Pace procedure than through the forced-choice format and (b) the reult of the forced-choice aement would better predict which timuli would reult in higher level of reponding in a concurrent operant paradigm. METHOD Subject and Setting Ava wa 2 year 9 month old and had evere mental retardation and a eizure diorder. Carl wa 5 year 6 month old and exhibited moderate mental retardation, organic brain yndrome, left hemiparei, a left viual field defect, and a eizure diorder. Don wa 7 year 1 month old and had profound retardation, microcephaly, right hemiparei, pervaive developmental diorder, and a eizure diorder. Kati wa 1 year old and exhibited evere mental retardation, Down yndrome, and hypothyroidim. All eion were conducted in individual treatment room (approximately 3 m by 3 m). Oberver recorded participant repone while eated in the room or from behind a two-way mirror. Data Collection and Reliability During timulu preference and forced-choice eion conducted in Phae 1, a trained oberver recorded whether the participant approached each item preented. A econd independent oberver collected reliability data during 8.2% of Phae 1 eion. The average agreement coefficient acro ubject were (a) occurrence, 94.6% (range, 87.9% to 97.4%); (b) nonoccurrence, 89.4% (range, 8.8% to 97.5%); and (c) total, 98.4% (range, 98.1% to 98.8%). During Phae 2 for Ava, Carl, and Kati, two quare (.7 m by.7 m) were drawn on the floor of the treatment room, and the trained oberver recorded on a laptop computer the duration of inquare behavior. In-quare behavior wa defined a having any body portion inide the quare. For Don, two chair were preent in the treatment room, and duration of in-eat behavior (buttock touching the eat of the chair) wa ued a the dependent variable. A econd independent oberver collected reliability data during 69.6% of Phae 2 eion. Exact interval-by-interval agreement coefficient

3 REINFORCER ASSESSMENT 493 were calculated for duration of in-eat or in-quare behavior by dividing the number of agreement by the um of agreement and diagreement and multiplying by 1. An agreement wa defined a a 1- interval during which both oberver recorded the ame duration (in econd) of the target behavior. In Phae 2, the average exact agreement coefficient acro client wa 97.6% (range, 95.3% to 99.5%). Procedure Phae 1. The timuli ued in the Pace et al. (1985) tudy were compared uing the timulu preference procedure developed by Pace et al. and a forced-choice method of timulu preentation. The timuli were a mirror, a light box, taped muic, a beeper, coffee ground, hibicu, juice, a cracker, a vibrator, a fan, a heat pad, an ice pack, a rocking chair, a wivel rocker, a therapit dapping, a hug from the therapit. For the timulu preference aement, the 16 timuli were individually preented a total of 1 time each over the coure of eight eion. Within a eion, four timuli were preented five time each in a counterbalanced order. For each trial, one timulu wa placed approximately.7 m in front of the client. Client approache reulted in acce to the timulu for approximately 5. If a client did not approach a timulu after 5, the therapit prompted the client to ample the timulu for 5. After ampling the item, it wa again placed.7 m in front of the client for another 5 ; an approach reulted in acce to the timulu for 5. During the forced-choice aement, the ame 16 timuli were preented in pair. Each timulu wa paired once with every other timulu, in a randomized order, for a total of 12 timulu-pair preentation. For each trial, two timuli were placed.7 m apart and approximately.7 m in front of the dient. Client approache to one of the timuli reulted in acce to that timulu for 5 and removal of the other timulu. Client approache to both timuli imultaneouly were blocked. If a client did not approach either timulu within 5, the therapit prompted the client to ample each timulu for 5. After ampling each item, the two timuli were again placed in front of the client for another 5. Client approache to one of the timuli reulted in acce to that timulu for 5 and removal of the other timulu. If the client did not approach either item within 5, both item were removed, and the next trial began. Phae 2. The initial plan wa to compare three type of timuli: (a) timuli approached on at leat 8% of trial on both timulu preference and forcedchoice aement (high-high timuli), (b) timuli approached on at leat 8% of timulu preference trial and 6% or fewer forced-choice trial (SPhigh timuli), and (c) timuli approached on at leat 8% of forced-choice trial and 6% or fewer timulu preference trial (FC-high timuli). However, the reult of Phae 1 produced high-high timuli and SP-high timuli, but no FC-high timuli. Therefore, only high-high and SP-high timuli were compared in Phae 2. The pecific timuli elected by each client a high-high and SP-high are available from the author upon requet. When multiple timuli met criteria for a highhigh timulu, two timuli with the greatet agreement between the timulu preference and forcedchoice aement were elected. When multiple timuli met criteria for SP-high, two timuli with the greatet diagreement between the timulu preference and forced-choice aement were elected. For Ava, only one timulu met the SP-high criterion; therefore, the timulu that mot doely approximated the criterion wa induded o that there would be a pair of SP-high timuli (thi additional timulu wa approached on 75% of the timulu preference trial and only 16% of forcedchoice trial). During both the initial and return-to-baeline eion, a therapit wa preent in the treatment room but did not interact with the client. None of the timuli were preent during baeline. Following baeline, the client received training trial to teach him or her to gain acce to the timuli being aeed. A training trial conited of placing the timuli in a box (or chair) in front of the dient. The client wa given 5 to move into the box or

4 494 WAYNE FISHER et al. chair independently and then given equential verbal, getural, and phyical prompt every 5 until the client diplayed the target repone. Immediately after diplaying the target repone, the client wa given acce to the timuli for approximately 1. Training ended when the client emitted the target repone independently on 8% of trial for three conecutive block of 1 trial. During treatment, eion were conducted in a manner identical to baeline except that two timuli were poitioned in each of the boxe on the floor or directly next to each of the chair. The two highhigh timuli were placed with one box or chair, and the two SP-high timuli were placed with the other box or chair. The client could gain acce to high-high or SP-high timuli by engaging in independent in-quare or in-chair behavior in the correponding box or chair on which thoe timuli were placed. That i, if the client exhibited in-quare or in-chair behavior, the therapit preented the timuli aociated with that quare or chair to the client. If the client left a box or chair for 3, the therapit withdrew the timuli and returned them to the deignated box or chair. RESULTS The reult from Phae 1 are preented in Figure 1. The type of timulu i repreented by a letter (A through P) poitioned below the abcia. In the left panel, timuli are preented from left to right, rank-ordered according to the approach repone meaured during the forced-choice aement. In the right panel, the ame data are preented rank-ordered according to the approach repone meaured during the timulu preference aement. The data are preented in thi format to highlight the imilaritie and difference between the two aement. There were nine timuli identified a highly preferred by both aement for the 4 client. Thee were the only nine timuli identified a highly preferred by the forced-choice aement. There were 27 additional timuli identified a highly preferred by the timulu-choice aement, 19 ofwhich met criteria for an SP-high timulu (i.e., approached on 8% or greater timulu preference trial and 6% or fewer forced-choice trial). The chance probability that all 19 diagreement would be SPhigh timuli and none would be FC-high timuli i exceedingly low (Z = 4.36; p <.1). The reult of Phae 2 are depicted in Figure 2. For all 4 client, the duration of in-eat and inquare behavior wa ignificantly higher when thee behavior reulted in acce to high-high timuli than during baeline. The duration of in-eat and in-quare behavior wa omewhat higher than baeline for Carl when thi behavior reulted in acce to SP-high timuli, and wa unchanged for Don and Kati or wa lightly lower than baeline for Ava. Finally, within the concurrent operant phae, the duration of in-eat and in-quare behavior wa ignificantly higher for the chair or quare aociated with high-high timuli than for the chair or quare aociated with the SP-high timuli. DISCUSSION In Phae 1 of thi invetigation, a comparion of two timulu aement howed that (a) all of the item identified a highly preferred by the forcedchoice aement were alo identified a highly preferred on the timulu preference aement and (b) on all of the timuli for which the two aement diagreed, the timulu preference aement identified the item a highly preferred and the forcedchoice aement identified the item a low to moderate. Thee reult ugget that the forced-choice aement ha good concurrent validity and that the timulu preference aement tend to identify timuli a highly preferred too often. Thi may occur becaue the timuli are preented individually, and alternative timuli are not available to the client. Although the forced-choice format appear to be a ueful extenion of the Pace et al.(1985) procedure, the original procedure may till be preferable with extremely low functioning individual who have difficulty making reliable choice repone. In Phae 2, timuli on which the two procedure agreed (high-high timuli) and diagreed (SP-high timuli) were compared uing a concurrent operant

5 CO) LU In z cnm a: CO) 1 O o OI 4 2 ORDERED BY FORCED CHOICE H Forcd Choice H H S Eumulue Preference.j L., rl - - I- LL- gm- I- *4 F w H H G'N'M'J 'C 'uda'i L'5'nIEtOuIr IF I 1 m o 4 DO 4 ORDERED BY STIMULUS PREFERENCE 11111iI I I _%. _AfI.. _., c%#, f N L p E F /K /13 /H,,, I,mI...- L In 4c 1 U U 14 ri H S 1 oz U I I. I- z In C) In a. 4 2 lo U C%1-1. L i- F. /P H H H SS S S _ io a L a /M /N I /K/ o o 4 2 a K I L i A P E/F/ 4 S STIMULI Figure 1. The percentage of approach repone to each of the 16 timuli during the forced-choice and timulu preference aement conducted in Phae 1. An H above a timulu indicate that the timulu meet criteria a a high-high timulu; an S indicate that the timulu meet criteria a an SP-high timulu.

6 496 w F LI. Lu O 1 8 C6* X 4 &M co en U) 2 BASEUNE WAYNE FISHER et al. CONCURRENT OPERANTS BASEIUNE CONCURRENT OPERANTS BASEUNE BL I- z w ( uj. (U) ne BASEUNE ONCURRENTOPERANTS BASEUNE Z 6 2E SESSIONS Figure 2. The percentage of time each client engaged in the in-quare or in-chair behavior aociated with high-high and SP-high timuli during the baeline and concurrent operant condition.

7 REINFORCER ASSESSMENT 497 paradigm. For all 4 client, greater increae in reponding occurred with high-high timuli than with SP-high timuli, indicating that the forcedchoice aement better predicted which timuli would function a more potent reinforcer when a concurrent operant paradigm wa ued a the criterion (i.e., the forced-choice aement had better predictive validity). A concurrent operant paradigm wa ued becaue it i efficient and allow comparion of reinforcer or chedule that cannot be accomplihed in a paradigm in which operant are evaluated at different point in time (i.e., in a ingle operant paradigm). The concurrent operant paradigm ha been employed primarily in baic operant reearch on chedule of reinforcement, but the current reult ugget that it may alo be ueful for aeing reinforcer for clinical purpoe. The advantage of thi paradigm for aeing the relative trength of two or more reinforcer i that the magnitude of reponding for each operant i a function of the magnitude of reinforcement and type of chedule employed (interval or ratio) and i not related to interference or competition between the repone (Catania, 1966). When concurrent repone are reinforced on variable-interval (VI) chedule, the magnitude of each repone i directly proportional to, or matche, the magnitude of reinforcement aociated with that repone. When concurrent repone are reinforced on ratio chedule, the ubject will generally maximize reinforcement by emitting only the repone aociated with the denet chedule of reinforcement (Hermutein, 197). Neither the matching nor maximizing phenomenon occur when operant are tudied individually, in that large increae in reinforcement magnitude may produce only mall change in the magnitude of reponding (Catania, 1966). In Phae 2 of the current invetigation, client repone were reinforced on a ratio chedule (i.e., continuou reinforcement). Three of 4 client (Ava, Don, and Kati) reponded in a manner conitent with maximization, in that almot all of their inquare or in-eat behavior occurred in the quare or chair aociated with the high-high timuli. It i poible that the SP-high timuli would have produced ome increae in reponding for thee 3 client if the concurrent operant were reinforced on equal VI chedule, or if the SP-high timuli were preented in a ingle operant paradigm. Baed on the baic operant literature, ue of concurrent VI chedule may be mot appropriate when the clinician wihe to determine the relative preference value of two or more timuli (through the matching phenomenon). Ratio chedule may be mot appropriate when the clinician wihe to identify quickly the timulu with the highet preference value (through the maximization phenomenon). Ue of a ingle operant paradigm may be mot appropriate when the clinician wihe to determine whether each individual timulu can function a a reinforcer. For Carl, maximization did not occur, and both high-high and SP-high timuli produced only moderate increae in in-quare behavior during the concurrent operant phae, with the mean duration of in-quare behavior being omewhat higher for the high-high timuli. There are at leat two poible explanation of Carl' reult: (a) A Maon et al. (1989) found, preference may change over time for ome client and (b) none of the 16 timuli compared in thi invetigation were among Carl' mot preferred timuli. The forced-choice or timulu preference aement can identify reinforcer from thi or any et of timuli only if one or more of the timuli in the et are, in fact, reinforcer for a given individual. Green et al. (1991) found that ue of a imilar et of 12 timuli reulted in identification of reinforcer for mot, but not all, client. They alo found that caregiver opinion may be a ueful adjunct for the minority of client for whom none of the tandard timuli function a reinforcer. Future invetigator may wih to determine how to bet integrate caregiver information with tandardized reinforcer aement procedure. The comparion in Phae 2 would have been trengthened if ingle example of high-high and SP-high timuli were compared, rather than preenting the timuli in pair. The Phae 2 procedure were baed on our normal clinical practice in which we routinely preent multiple preferred timuli to increae the probability of a reinforcement effect. Given that client preference change over time (Maon et al., 1989), thi eem to be a reaonable

8 498 WAYNE FISHER et al. trategy. However, it i not poible to draw conduion about individual timuli when uing thi procedure. Future invetigator may wih to determine the extent to which the forced-choice aement accurately predict the reinforcement effect of individual timuli. REFERENCES Catania, A. C. (1963). Concurrent performance: A baeline for the tudy of reinforcement magnitude. Journal ofthe Experimental Analyi ofbehavior, 6, Catania, A. C. (1966). Concurrent operant. In W. K. Honig (Ed.), Operant behavior: Area of reearch and application (pp ). New York: Appleton-Century-Croft. Charlop, M. H., Kurtz, P. F., & Caey, F. G. (199). Uing aberrant behavior a reinforcer for autitic children. Journal of Applied Behavior Analyi, 23, Dattilo, J. (1986). Computerized aement of preference for everely handicapped individual.journal ofapplied Behavior Analyi, 19, Green, C. W., Reid, D. H., Canipe, V. S., & Gardner, S. M. (1991). A comprehenive evaluation of reinforcer identification procee for peron with profound multiple handicap. Journal ofapplied Behavior Analyi, 24, Green, C. W., Reid, D. H., White, L. K., Halford, R. C., Brittain, D. P., & Gardner, S. M. (1988). Identifying reinforcer for peron with profound handicap: Staff opinion veru ytematic aement ofpreference.journal of Applied Behavior Analyi, 21, Herrntein, R. J. (197). On the law of effect. Journal of the Experimental Analyi of Behavior, 13, Maon, S. A., McGee, G. G., Farmer-Dougan, V., & Riley, T. R. (1989). A practical trategy for ongoing reinforcer aement. Journal ofapplied Behavior Analyi, 22, Pace, G. M., Ivancic, M. T., Edward, G. L., Iwata, B. A., & Page, T. J. (1985). Aement of timulu preference and reinforcer value with profoundly retarded individual. Journal of Applied Behavior Analyi, 18, Steege, M. W., Wacker, D. P., Berg, W. K., Cigrand, K. K., & Cooper, L. J. (1989). The ue of behavioral aement to precribe and evaluate treatment for everely handicapped children. Journal of Applied Behavior Analyi, 22, Wacker, D. P., Berg, W. K., Wiggin, B., Muldoon, M., & Cavanaugh, J. (1985). Evaluation of reinforcer preference for profoundly handicapped tudent. Journal of Applied Behavior Analyi, 18, Received September 7, 1991 Initial editorial deciion November 8, 1991 Reviion received December 3, 1991 Final acceptance February 18, 1992 Action Editor, David P. Wacker