Adjunctive behavior in children on fixed interval food reinforcement schedules

Phystology& Behavtor, Vol. 28, pp. 609-612 PergamonPress and Brain Research Publ, 1982. Printed m the U S A.

Adjunctive Behavior in Children on 1 Fixed Interval Food Reinforcement Schedules J O S E P H H. PORTER, R. T O D D B R O W N A N D P E T E R A. G O L D S M I T H

D e p a r t m e n t o f Psychology, Virginia C o m m o n w e a l t h University, R i c h m o n d , VA 23284 R e c e i v e d 7 O c t o b e r 1981 PORTER, J. H , R. T. BROWN AND P. A GOLDSMITH. Adjunctive behavior in children on fixed mterval food remforcement schedules. PHYSIOL. BEHAV. 28(4)609-612, 1982.--Four female children (4 to 6 years of age) were tested on fixed interval (FI) 30-sec and 60-sec food schedule with M&M candy reinforcers. All four subjects displayed increased movement on the FI schedules as compared to appropriate FR 1 basehne conditions. Increased dnnking was shown by three subjects, and increased vocahzations by two subjects. These results clearly demonstrated schedule-induced behaviors m children with food reinforcement schedules which are typically used m animal experiments. Adjunctive behaviors Schedule-reduced behaviors Movement Dnnkmg Vocahzations

W H E N a food-deprived rat is placed on an intermittent food reinforcement schedule (following a baseline period of massed-feeding), increases in non-reinforced behaviors may be observed. This class of behaviors has been termed adjunctive by Falk [5] as the behaviors occur as adjuncts to the behavior which is under schedule control. Many of the determinants of adjunctive behavior have been identified, and it has been demonstrated that many different behaviors may be schedule-induced. F o r example, intermittent food schedules can lead to polydipsia (e.g., [3,4]), wheel running [12,14], air licking [15], pica [19], and aggression (e.g. [1, 8, 9]). Also it has been demonstrated that the schedule presentation o f reinforcers other than food can induce adjunctive behavior [12,18]. According to Wayner [23,24], any type of intermittent stimulation should induce adjunctive behavior because of an increase in motor excitability. Recently, adjunctive behavior investigations have been extended to include the study o f human subjects. However, the procedure for inducing adjunctive behaviors in human studies has usually differed from that in animal studies in two important respects. First, human subjects are typically not in a deprived state and, second, conventional primary reinforcers (such as food or water) are not usually employed (e.g., [10]). The research strategy instead has been to limit the opportumty of making a response, typically in a game playing situation (e.g., [2, 20, 22]). This procedure has been successful in inducing such behaviors as pacing and drinking [10], eating (and drinking) and grooming [6], smoking ]20] and gross body movements [2, 13, 22]. In studies which have employed secondary reinforcers (such as tokens) schedule induced aggression [7,11] and body movement [16], have been observed. Only one study has used a conventional food reinforcement schedule with human subjects. Wallace, Samson, and Singer [21] tested adult humans (18 to 21 years) and found that movements were significantly greater when food

Chddren

Fixed interval food schedules

was available during ad lib conditions or on a fixed interval (FI) 60-sec food delivery schedule than when food was not available. However, there was no significant difference between the FI condition and the ad lib food condition. Therefore, there was no clear demonstration that movements were schedule-induced when food was made available on the F I schedule. Another criticism of human adjunctive behavior studies has been advanced by Fallon, Allen, and Butler [6]. Fallon et al. note that in animal research, the animal typically has free access to a reinforcer which is later placed under schedule control. In human studies, however, either the subjects are not exposed to a massed-feeding or continuous reinforcement baseline (e.g., [10, 13, 16, 21]), or the baseline task is unrelated to the task employed in the schedule inducing session (e.g., [2, 20, 22]). In the absence of an appropriate baseline measure, the responses observed by these researchers cannot correctly be termed adjunctive behaviors. Fallon et al. [6], in an attempt to resolve some of the problems of previous human studies, investigated adjunctive behavior during game playing using a typical design seen in many animal studies. Subjects and confederates played three games of backgammon. The first game was played conventionally and served as a baseline. In the second game, a curtain was placed between the players to block visual access to the opponent's moves, the board being passed under the curtain following each move. The confederate timed each of his moves to take 30 seconds, effectively introducing F I 30-sec schedule, before returning the board to the subject. The third game was again played conventionally and served as a second baseline. The results showed significant increases in movement, eating, drinking, and grooming between the first baseline and schedule controlled games, and significant differences in eating, drinking, and grooming between the second baseline and

1Send reprint requests to Joseph H. Porter, Department of Psychology, Virginia Commonwealth University, Richmond, VA 23284.

C o p y r i g h t © 1982 B r a i n R e s e a r c h P u b l i c a t i o n s Inc.--0031-9384/82/040609-04503.00/0

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PORTER, BROWN A N D G O L D S M I T H

schedule controlled games. Fallon et al. [6] interpreted their results as demonstrating that an animal paradigm is effective in inducing adjunctive behaviors in humans, and proposed extending the animal paradigm further in studying human adjunctive behavior. The purpose of the present study was to further explore adjunctive behaviors in human subjects with a food reinforcement schedule, since food schedules have typically been used in animal studies. Children were tested on fixedinterval (FI) food reinforcement schedules and on appropriate FR 1 baselines both before and after the FI schedules.

METHOD SubJects Four female children (ages 4, 41/2, 5 and 6) served as subjects. Apparatus Testing apparatus included a telegraph key and an M&M dispenser (Davis Scientific Instruments, Model MMD-1) which were mounted on a table in front of the seated subject. There was a red light located over the M&M dispenser. Electromechanical programming equipment was located in an adjacent room which had a one-way mirror for observation. Plan M&M candy (M&M-Mars) served as reinforcers. Subjects were offered a choice of one of several different soft drinks after initial familiarization (see Table 1) with the food reinforcement schedules. The soft drink was provided in a 12 oz paper cup. This was enough soft drink for the entire Test Period (see Table 1). Procedure The children were seated in front of the telegraph key and M&M dispenser and were familiarized with the equipment and were told that they could obtain M&Ms by pressing the telegraph key whenever the red light over the food magazine was on. They were give a brief description of how the telegraph key worked and how pressing it would deliver M&Ms. The experimenter explained to them that sometimes M&Ms would be delivered every time they pressed the key and sometimes they would have to press the key many times before they earned an M&M. Then the experimenter left the room. For two children, their mother remained in the room with the child, seated quietly in a corner. After a two-minute free operant period, the red light over the food magazine was turned on and the initial familiarization with the food reinforcement schedules began. Table 1 shows the order of presentation of the food reinforcement schedules for this Familiarization Period when no soft drink was available and for the Test Period when the soft drink was available. After the Familiarization Period was over, the subjects were provided with a soft drink in a paper cup and observed for two minutes before the Test Period began. The red light over the food magazine was off during this two minute period and no M & Ms were available. The children were observed by an experimenter from an adjacent room through a one-way mirror. Recorded behaviors included barpressing, movements, drinking, and vocalizations. A movement was recorded for any motor activity other than barpressing. No attempt was made to differentiate between fine and gross movements, although very subtle movements (such as eyeblinks) were not counted. A drink

TABLE 1 SCHEDULES OF REINFORCEMENT, THE LENGTH OF TIME EACH WAS IN EFFECT, AND THE NUMBER OF M&Ms WHICH WERE DELIVERED ARE SHOWN FOR THE FAMILIARIZATION PERIOD AND THE TEST PERIOD (WHEN SOFT DRINK WAS AVAILABLE) Schedule of Remforcement

Time

Number of M&Ms Dehvered

Famlltanzatlon Period Fixed Ratio 1 Fixed Interval 30-sec Fixed Interval 60-sec

2-mm 2-ram 4-min

10 M&Ms 4 M&Ms 4 M&Ms

Test Period Fixed Ratio 1 (Basehne) Fixed Interval 30-sec Fixed Ratio 1 (Baseline) Fixed RaUo 1 (Baseline) Fixed Interval 60-sec Fixed Ratio 1 (Basehne)

5-mm 5-mm 5-mln 5-mm 5-min 5-mln

10 M&Ms 10 M&Ms 10 M&Ms 5 M&Ms 5 M&Ms 5 M&Ms

was recorded each time the child placed the cup to the mouth and then removed it. A vocalization was recorded any time the child made a verbal utterance (e.g., questions, comments, singing, or any audible sound which could be detected by the experimenter in the adjacent room). The entire session last approximately 50 minutes. RESULTS Table 2 shows the total number of movements for each subject for each reinforcement schedule during the Test Period. Except for S-l, all subjects displayed substantial increases in movements during the FI 30-sec food schedule as compared to the initial and subsequent F R 1 baselines. All four subjects showed large increases in movements when shifted from F R 1 to F I 60-sec and substantial declines when returned to the FR 1 baseline condition. For drinking the results were less consistent (See Table 3). Three subjects (S-I, S-2, and S-4) showed an increase in drinking when the FI 30-sec food schedule was in effect; however, only S-1 and S-4 approximated baselines levels of drinking when returned to the FR 1 schedule. Only S-1 and S-3 displayed a reliable increase in drinking on the FI 60-sec schedule as compared to the two F R I baseline conditions. Table 4 shows the number of vocalizations made by each subject during each reinforcement schedule during the Test Period. No systematic changes in vocalizations occurred when the F I 30-sec schedule was in effect. However, subjects S-1 and S-4 displayed an increase in vocalizations when switched from F R 1 to F I 60-sec, and a subsequent reduction when the F R 1 schedule was reinstated. DISCUSSION In the present study four children displayed scheduleinduced movement, drinking and vocahzations on fixedinterval food reinforcement schedules. While previous studies have demonstrated adjunctive behaviors in humans (e.g., [6,22]), this was the first to do so using a conventional primary reinforcer (i.e., food). Schedule-induced movement

A D J U N C T I V E B E H A V I O R IN C H I L D R E N

611

TABLE 2 TOTAL NUMBER OF MOVEMENTS FOR FI 30-SEC AND FI 60-SEC SCHEDULE CONDITIONSAND THE FR 1 BASELINES

TABLE 4 TOTAL NUMBEROF VOCALIZATIONSFOR F130-SECAND F160-SEC SCHEDULE CONDITIONSAND THE FR 1 BASELINES

Movements

Vocalizations

Subjects

FR l

S-1 S-2 S-3 S-4

45 16 34 45

Mean

35.0

FI 30-sec

FR 1

FR 1

49 47 75 65

30 26 37 40

24 28 26 40

59.0

33.3

29.50

FI 60-sec

FR 1

Subjects

51 64 60 79

24 32 32 42

S-1 S-2 S-3 S-4

63.5

32.5

Mean

TABLE 3 TOTAL NUMBER OF DRINKS FOR FI 30-SEC AND FI 60-SEC SCHEDULE CONDITIONSAND THE FR 1 BASELINES Drinks Subjects

FR 1

S-I S-2 S-3 S-4

0 0 14 4

Mean

4.5

FI 30-sec 10 8 11 10 9.3

FR 1 FR 1 2 6 5 3

5 5 6 0

4.0

4.0

FI 60-sec 13 3 11 0 7.3

FR 1 3 1 1 0 1.3

was the most consistent adjunctive behavior for the four subjects during the FI 30-sec and FI 60-sec reinforcement schedules; whereas, drinking and vocalizations were not as reliably induced by the food schedules. Two defining characteristics of adjunctive behaviors are their excessiveness and their occurrence during the postpellet portion of the interreinforcement interval [5]. The excessiveness of the behavior during the intermittent reinforcement schedule is usually defined in terms of a massedfeeding or a continuous reinforcement baseline. As Fallon et al. [6] have pointed out, most humans studies on adjunctive behaviors have failed to use appropriate baselines. The pres-

FR 1 13 0 9 2 6.0

FI 30-sec 16 0 14 2 8.0

FR 1 FR 1 8 1 13 2 6.0

7 1 18 4 7.5

FI 60-sec 20 6 17 17 15.0

FR 1 12 6 15 6 9.8

ent study and the study by Fallon et al. [6] have clearly demonstrated that certain behaviors (i.e., movement, drinking, vocalizaitons, grooming, and eating) can be induced by intermittent reinforcement schedules and are excessive in nature when appropriate baselines are used for comparison. While the temporal distribution of the adjunctive behaviors in the present study was not recorded, Fallon et al. [6] failed to find any evidence in their study of the post-pellet pattern which is typically reported in animal studies (see 5; although wheel running has been reported as an exception, [17]). They suggested that it may be necessary to use interreinforcement intervals greater than one minute with humans before the typical post-pellet distribution will emerge. In order to fully understand the nature o f adjunctive behaviors with humans it will be necessary to examine those variables which have been shown to be important in animal studies. For example, adjunctive behaviors are known to vary as a function of the length of the interreinforcement interval and the level of deprivation of the subjects [5]. Neither variable has been systematically explored with human subjects. Another important difference between human and animal studies concerns the manner in which test sessions are conducted. In animal studies test sessions are conducted daily and the adjunctive behaviors typically emerge over a period o f several sessions. In human studies, however, usually only one extended test session is conducted. If human studies are conducted in the same manner as animal studies, the generality and similarity of adjunctive behaviors in humans should be even more evident than that reported in the present study.

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