The role of verbal behavior in human learning: II. Developmental ...

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1985,

JOURNAL OF THE EXPERIMENTAL ANALYSIS OF BEHAVIOR

439 165-181

NUMBER

2

(MARCH)

THE ROLE OF VERBAL BEHAVIOR IN HUMAN LEARNING: H1. DEVELOPMENTAL DIFFERENCES R. P. BENTALL, C. FERGUS LOWE, AND ALLAN BEASTY UNIVERSITY COLLEGE OF NORTH WALES

When children in four different age ranges operated a response device, reinforcers were presented according to fixed-interval schedules ranging in value from 10 to 70 seconds. Only the behavior of the subjects in the youngest of the four groups, the preverbal infants, resembled that of other animal species. The children in age ranges 5 to 6 1/2 and 7 /2 to 9 years exhibited either the low-rate or high-rate response patterns typical of human adults. Those who showed the low-rate pattern reported a time-based formulation of the contingencies and some of them were observed to occasionally count out the interval before responding. The performance of children aged 2 Y2 to 4 years differed from that of both infants and older children, though containing some patterniing elements similar to those produced by the older and younger subjects. The predominant response pattern of the infants consisted of a pause after reinforcement followed by an accelerated rate of responding that terminated when the next reinforcer was delivered. Analysis of postreinforcement-pause duration and response rate showed that infant performance, but not that of the older children, consistently exhibited the same kinds of schedule sensitivity observed in animal behavior. The evidence supports the suggestion that the development of verbal behavior greatly alters human operant performance and may account for many of the differences found between human and animal learning. Key words: verbal behavior, developmental differences, learning, fixed interval, scalloping, postreinforcement pause, response rate, lever press, children

A considerable amount of experimental evidence now indicates that there are major differences in the ways in which reinforcement affects human and animal behavior (cf. Lowe, 1979; Matthews, Shimoff, Catania, & Sagvolden, 1977). Lowe (1979, 1983) has suggested that human language may be the principal factor involved in these differences. Through participation in a verbal community humans acquire the skill of describing their environment and themselves, of formulating verbal rules, and of acting in accordance with these rules. This use of language is unique among living creaSome of these data were presented at meetings of the Experimental Analysis of Behaviour Group (UK) in 1980 and 1981. During the study R. P. Bentall and A. Beasty were in receipt of graduate studentships from the Science and Engineering Research Council and the University College of North Wales, respectively. Special thanks are due to all the parents and children who have been concerned with this study. Reprint requests may be sent to C. F. Lowe, Department of Psychology, University College of North Wales, Bangor, Gwynedd LL57 2DG.

tures and has profound effects upon much of human activity, including performance on schedules of reinforcement (see Skinner, 1945, 1974). If this account is correct, a number of clear predictions can be made about the development of human operant behavior. First, the schedule performance of infants, who have not yet acquired the relevant verbal skills, should show animal rather than adult human characteristics. In line with this prediction, our earlier study (Lowe, Beasty, & Bentall, 1983) showed that, in terms of both response patterning and schedule sensitivity, the performance of preverbal infants on fixed-interval (FI) schedules closely resembled that of animals under comparable conditions but was very different from that shown by adult humans. A number of studies have shown that under conventional Fl procedures adult human behavior bears little resemblance to that of animals and often takes one of two forms -either a continuous and high rate of responding (the high-rate

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pattern) or a very low response rate consisting of just one or two responses at the end of the interreinforcement interval (the lowrate pattern); the FI scallop, together with the sensitivity of performance to variations in schedule value that is characteristic of animal behavior, is virtually never seen (Leander, Lippman, & Meyer, 1968; Lowe, 1979; Weiner, 1969). Second, one might also predict that as language skills become established, the performance of children on schedules of reinforcement will differ increasingly from the classic animal pattern and will come to resemble the behavior of adult humans. Both of these predictions were tested in the present study, which was an investigation of the behavior of children of different ages on FI schedules of reinforcement. The verbal behavior of children in two of the groups, the 7 2 to 9 and 5 to 6 2-year-olds, was well advanced, whereas the youngest group of subjects were preverbal infants. The children in the fourth group, aged 2½2 to 4 years old, had some language although previous research, particularly by Soviet psychologists, suggests that verbal control of behavior is poorly developed in children of this age (Bem, 1967; Luria, 1961; Vygotsky, 1962). Although there have been some studies of schedule performance in children (e.g., Long, Hammack, May, & Campbell, 1958), the possibility that there might be developmental differences appears to have gone almost completely unrecognized; presentation of data has included no pertinent consideration of subjects' ages or, perhaps more importantly, of their ability to describe the experimental conditions. This would seem to be characteristic of an approach, present within the experimental analysis of behavior, that is reluctant to go beyond the findings of animal research in constructing a theory of human behavior. Inasmuch as the behavioral relationships in schedule performance have been treated as substantially the same in both animals and humans, of whatever age, perhaps it is thought that developmental differences within human operant

performance either do not exist or are insignificant. The present study questions these assumptions. METHOD

Subjects Children in four age ranges took part. The three children in Group 1, two boys and one girl, were between 7 Y2 and 9 years of age at the start of the experiment. The two girls and one boy in Group 2 were between 5 and 61/2 years, and the Group 3 children, two girls and a boy, were between 2 /2 and 4 years. There were four infants, one girl and three boys between 6 months and 1 /2 years of age, in Group 4. Detailed results from two of these subjects, Ann and Jon, have previously been presented by Lowe et al. (1983), but, for comparison purposes, some of their data will be reshown here. The ages of individual subjects and their scores on the Reynell Developmental Language Scale (RDLS; see Reynell, 1977) are given in Table 1. The subjects were recruited through local schools, nursery groups, and advertisement in local newspapers. The RDLS is a developmental test of language skills that has been standarized on a sample of 1,318 British children; its aim is to measure expressive language and verbal comprehension. The performance measures include tests of naming, vocabulary, and descriptive speech. Additional items require the child to follow instructions on tasks of progressively increasing complexity. Apparatus For all subjects in Groups 1 to 3, the experiment was conducted in the psychology laboratories at the University. The apparatus shown in Figure 1 was situated in a room that had been decorated with posters of cartoon characters. The children sat at a table in front of a large wooden screen near the center of which was mounted a vertical column of 10 colored lights that could be illuminated in sequence from bottom to top, the entire sequence taking 8 s. To one side of the column of lights there was a translucent

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Table 1 Age and score on the Reynell Developmental Language Scale (RDLS), in years and months, of each subject. The maximum score obtainable on RDLS is 7 years. Subject Group Age RDLS Score = 1 LR 7.0 7.6 SR 8.3 7.0 IP 8.7 7.0 HP 2 5.3 6.9 LC 5.9 6.6 MK 6.6 7.0 SM 3 2.6 2.9 TS 4.3 3.10 4.0 3.9 Ji 4 Jon 0.9 Pat 0.9 Ann 0.10 Will 1.1

acrylic screen (28 by 20 cm) on which slides could be back-projected. The slides used were in story sequences and depicted cartoon characters such as Winnie the Pooh, Donald Duck, and The Lone Ranger. Slide projection was accompanied by pop music played on a tape-recorder behind the screen. On the other side of the column of lights was mounted a black plastic tube through which snack items could be dropped by a glove puppet, "Sooty," into a tray on the table; Sooty was operated by the experimenter who remained out of sight behind the screen. A lever was mounted on a small console in the middle of the table and could be operated by a force of 6.7 N, producing an audible click. The experiment was controlled by, and data were recorded on, an Apple II microcomputer situated behind the wooden screen. In order to avoid a number of practical problems (see Long et al., 1958), the sessions with infants were conducted in their own homes and portable equipment was therefore used for these subjects. The response device employed with Ann, Jon, and Pat was a metal cylinder 40 cm long and 11 cm in diameter, mounted on a wooden stand. The cylinder was placed within reach of the child who sat in a high chair (Ann and Pat) or on mother's knee (Jon). When the cylinder was touched, an electronic touch

Fig. 1. Apparatus employed with the three oldest groups of children. The subject shown here is holding the response device (lever) in his left hand. switch was activated and the response was registered in an Apple II microcomputer. The fourth infant, Will, sat in a high chair in front of which was placed a manipulanduin, consisting of a small sphere (10 cm in diameter) mounted on a telegraph key, that could be operated by a force of 1 N. For all four infants, each response produced an audible click. Reinforcer delivery was signaled by a brief tone from the microcomputer according to the particular schedule in operation. A portable light unit was employed with some of the infants. This consisted of a small box (23 by 13 by 13 cm) on which was mounted a row of 6 colored lights that could be illuminated in sequence, each sequence lasting 5 s. Illumination of the lights was accompanied by music played on a portable tape-recorder. Procedure The children in Groups 1 to 3 were introduced to the experimental situation in the company of a familiar adult, usually a parent, whose presence was not required

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after the first one or two sessions. At the beginning of the first session the experimenter sat in front of the screen and pulled the manipulandum once, which produced the reinforcer. He then said to the child, "Look what happens when I pull the lever. Now you have a go." The experimenter then went behind the screen and the subject was left to respond on continuous reinforcement (CRF) until 10 reinforcers had been produced. This was usually followed by a period in which the subject performed on FI 20 s before the schedule value was increased to 40 s. In some cases (IP, LC, HP, TS, JJ, and SM) this happened over a number of sessions, but other subjects (SR, LR, and MK) were introduced to FI 40 s immediately following performance on CRF. Subsequently, reinforcers were presented on FI schedules ranging in value from 25 to 70 s; schedule values were changed when inspection of the cumulative records showed responding to be stable over three consecutive sessions (see Table 2). Sessions typically lasted from 10 to 15 min and were conducted 3 or 4 days per week. For all children in Groups 1 to 3, reinforcement consisted of an illumination of the column of lights from bottom to top, a cartoon slide projected on the screen for 10 s accompanied by music, and the appearance above the screen of the glove puppet, Sooty, who greeted the child and dropped his/her favorite snack item (e.g., a piece of fruit, candy, potato crisp, etc.) down the tube into the tray where it could be collected and consumed by the child. In many of the experimental sessions the children's verbal behavior was tape-recorded while they performed on the FI schedule. After completing each schedule value, subjects were asked, "What makes Sooty work?" and similar open-ended questions; their replies were recorded. The general procedure employed with infant subjects is outlined by Lowe et al. (1983). Responding was shaped by the method of successive approximations and each occurrence of the response was reinforced in the first two sessions. Subsequently,

Table 2 Number of sessions conducted on each schedule value and standard deviation of postreinforcement pauses for each subject; corresponding means are presented in Figure 8. The order of schedule values is shown from top to bottom. The pause data are from the last three sessions on each FI value. FI Value (seconds) Sessions S. D. (seconds) Subject = Group 1 40 LR 10 10.36 70 5 12.38 5 25 12.68 40 5 7.46 40 SR 6 13.39 70 6 3.19 25 5 2.15 40 5 1.54 IP 40 5 9.81 70 5 14.23 5 25 12.44 40 5 9.94 Group 2 40 HP 7 14.78 70 5 21.83 5 25 10.42 40 5 9.54 40 LC 8 16.11 70 7 35.93 25 6 8.93 40 5 15.72 40 MK 14 12.45 70 5 20.17 25 5 8.11 40 7 17.16 Group 3 40 SM 23 12.55 70 7 18.59 7 25 19.71 40 7 14.34 40 TS 11 13.03 70 10 7.93 25 6 13.57 40 6 13.89 40 JJ 12 7.24 70 10 10.45 25 6 3.63 40 6 7.93 Group 4 20 Jon 18 6.0 30 11 7.0 10 11 3.6 20 Pat 14 7.0 60 9 14.8 40 9 12.5 Ann 20 10 4.8 10 10 1.5 30 6 5.4 20 Will 12 12.4 60 14 16.2 40 12 13.5

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Fig. 2. Cumulative records of responding for each subject in Groups 1 to 3 from some of the early sessions on FI schedules. The cumulative pen was offset with each reinforcement. The number adjacent to each record indicates the session from which the record was obtained. Records were chosen in order to indicate major changes in the development of response patterning. All records, except those labeled otherwise, are from FI 40-s schedules.

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reinforcers were presented on FI schedules ranging in value from 10 to 60 s, schedule value being changed when inspection of cumulative records showed responding to be stable over three consecutive sessions (see Table 2). There was considerable individual variation among infants with respect to events that could function as reinforcers; for example, feeding routines in some homes would either facilitate or rule out the use of food. We relied upon parents for initial guidance as to suitable reinforcers. The reinforcer for Pat and Will consisted of illumination of the row of lights on the portable light unit for 5 s accompanied by music and the presentation of a cuddly doll. ForJon the reinforcer consisted of small snack items; for Ann it was 4 s of music played on music boxes. RESULTS Figure 2 shows individual cumulative records from sessions early in the development of FI performance for all subjects in Groups 1 to 3. In the first FI session, two of

the three 7 /2 to 9-year-old children, SR and LR, showed the high-rate and low-rate patterns, respectively, that are characteristic of adult FI performance. The third subject, IP, showed the low-rate pattern by Session 5. In the 5 to 61/2-year-old group, there was evidence of scalloping in the performance of LC during the early sessions, particularly in Session 2; the patterning of both MK and HP was broken and irregular at first but after 5 to 8 sessions, the three children had begun to exhibit low-rate performance. All of the children in the 2 ½2 to 4-year-old group produced scalloped patterns of responding at some time during the development of Fl performance, although this did not persist for many sessions but gave way to an irregular and broken pattern. Similar transient scalloping has also been reported for young children by Long et al. (1958). The performance of children in the 2Y2 to 4-year-old group took several sessions to stabilize and this was also true of the four infants (see Table 2). Figure 3 shows cumulative records for two infants, Pat and Will, from sessions

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Fig. 4. Cumulative records of responding for each of the children in the 7 /2 to 9-year-old group: on Fl 25 s, first performance on FI 40 s (Fl 40a), second performance on FI 40 s (FI 40b), and on FI 70 s. The records are from the final sessions on each schedule value (see Table 2).

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10 MINUTES Fig. 5. Cumulative records of responding for each of the children in the 5 to 6 Y2 -year-old group: on FI 25 s, first performance on FI 40 s (FI 40a), second performance on FI 40 s (FI 40b), and on FI 70 s. The records are from the final sessions on each schedule value (see Table 2).

early in the development of FI 20-s performance. Some of the initial sessions contained bursts of responding following reinforcement; these bursts were often followed by periods of nonresponding and the next response was then reinforced. The rate of responding of both subjects increased after the early sessions and a pause-respond pattern developed following reinforcement. (For comparable records from Ann and Jon, see Lowe et al., 1983.) The final form of responding on each FI schedule for the 7 Y2 to 9-year-old children is shown in Figure 4, which presents cumulative records obtained from the final session on each schedule value. The two familiar

patterns of human adult FI behavior are evident. The high-rate pattern, which characterized SR's behavior from Session 1, persisted throughout the various schedule changes. The other two subjects, IP and LR, responded only once or twice in each interval and usually just after reinforcement became available. Studies of adult human FI performance have shown that whenever lowrate patterning is exhibited, subjects invariably report a time-based formulation of the contingencies and, often, that they counted out the interval before responding. On the other hand, subjects who produce the high-rate pattern usually report that they considered that more responses would pro-

DEVELOPMENTAL DIFFERENCES IN HUMAN PERFORAMNCE duce more reinforcers and so responded as fast as possible (see Leander et al., 1968; Lippman & Meyer, 1967; Lowe, 1979). A similar relationship between FI pattern and verbal reports was observed in the present study. Both IP and LR produced time-based formulations. IP reported, "After I've pressed the lever, Sooty goes to sleep and then I wait for a little while before waking him"; he also could be heard counting out the fixed interval in some of the early sessions. LR simply said, "I wait for a bit and then press the lever." When questioned about her performance, SR said, "I press as fast as possible." For the most part, subjects in this group emitted little overt verbal behavior during experimental sessions. Figure 5 shows that the low-rate pattern was produced by the three subjects in the 5 to 6 /2-year-old group on each of the FI schedules, the one exception to this being the performance of MK on FI 70 s. All three children reported time-based formulations of the contingencies, and stated that they waited for a time before responding. For example, LC said that "You have to wait a while to get Sooty to come." Their verbal behavior throughout the study included singing, talking to Sooty, and reciting rhymes. Some of the speech took the form of "magical mands" (Skinner, 1957); in the early sessions, for example, LC whispered to the manipulandum, "Work please. Work please. . . . Work when I say work. Why don't you work?" During some of the early sessions, two of the subjects, LC and HP, began to count aloud in each fixed interval; in both cases the emergence of counting was accompanied by a low-rate response pattern that persisted for the remainder of the study. Early in the third session, for example, HP paused after reinforcement and counted aloud to 10; she then pulled the manipulandum and received a reinforcer. In the following interval there was another pause in responding while she counted to nine very quickly, hesitated, and then said, "Ten," and pulled the manipulandum too early to receive the reinforcer. She then said, "Eleven, no ten, no fourteen," before counting to

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fourteen very quickly, after which she responded on the manipulandum and received a reinforcer. During the next interval she counted to fourteen, responded with no effect, and then counted to fifteen before responding yet again. Later in this session overt counting gradually faded out but responding continued to occur at a low rate. The final performance patterns of the 2 l/2 to 4-year-old children, shown in Figure 6, were very different from those of the older children. Nor did they resemble animal behavior, although it is possible to detect in these records some elements of both human adult and animal FI performance - for example, occasional scallops and occasional high-rate responding. But there were also some patterns not typically found in either human or animal behavior, such as bursts of responding after reinforcement followed by a pause and then another burst of responding, or, alternatively, a pause after reinforcement followed by a burst of responding and then another pause. The great variety of response patterning evident in the cumulative records was accompanied by widely varied verbal behavior. Throughout the experimental sessions and in subsequent interviews, none of the children articulated any coherent description of the contingencies, other than stating that pulling the lever made Sooty appear. During experimental sessions they sometimes sang, grunted, hummed tunes, made other noises (e.g., of motor cars and aeroplanes), and talked to the cartoon characters that decorated the walls of the experimental room or addressed various remarks to Sooty. A great deal of whispering took place which was difficult to decipher. Verbalizations directly related to schedule performance were recorded only for SM, who in addition to talking to Sooty and singing, also said after unsuccessful responses, "Can't do it.... Can't do it.. . . Can't.. .. I can't. . . . Can't. . . ." This subject also repeatedly wandered around the room during sessions and played with the seat cover, rotating it over and over again. The infants' final form of responding on each Fl schedule is shown in Figure 7. The

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predominant response pattern consisted of a pause after reinforcement followed by an accelerated rate of responding that terminated when the next reinforcer was delivered. The records are indistinguishable from those obtained from a great variety of animal species on FI schedules (cf. Richelle & Lejeune, 1979). Sensitivity of FI performance to the temporal parameter can be assessed by quantitative measures such as rate of responding

and duration of postreinforcement pause. In the case of animal subjects, running rate (i.e., response rate computed by excluding the postreinforcement pause) declines with increases in the FI requirement and, although the absolute duration of postreinforcement pause increases, the proportion of the fixed interval occupied by the pause decreases on longer FI values (Hanson, Campbell, & Witoslawski, 1962; Hanson & Killeen, 1981; Lowe, Harzem, & Spencer, 1979; Lowe &

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Wearden, 1981; Skinner, 1938; Starr & pauses for the children in each group as Staddon, 1974; Wilson, 1954). The left panel functions of FI value (standard deviations of Figure 8 shows mean postreinforcement are given in Table 2). In the two oldest

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of all four infants were less than the schedule value and increased systematically as a function of the FI requirement; the pause occupied a declining proportion of the interval with increasing FI value. The right panel of Figure 8 shows running rate on each of the FI schedules. The running rate of some of the subjects in the three oldest groups declined as a function of FI value, notably LR (Group 1), LC and HP (Group 2), and TS (Group 3); in the case of the remaining subjects, there was no consistent relationship. The response rate of the four infants, on the other hand, declined systematically with increasing FI value. Taking all the response data togethercumulative records, postreinforcement pause, and running rates only the performances of the infants consistently resembled those typical of animals. For this reason the infant data were submitted to an additional quantitative analysis that directly compared their performance with that of animals. Figure 9 shows mean pause durations from rats, pigeons, and infants, plotted as a function of Fl value in logarithmic coordinates. The rat and pigeon data are means representing the stable performance of a group of four rats and four pigeons at different Fl values (see Lowe et al., 1979, for further details). The data from all three groups of subjects are well described by a power function, where Y is duration of postreinforcement pause and X is FI value, and k and n are empirically determined; in each case the regression equation accounts for 98% of the variance. The fractional exponents, with n ranging from 0.62 to 0.67, are typical of functions obtained from animals in studies of temporal discrimination (see Catania, 1970; Lowe et al., 1979).

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Fig. 8. Mean duration of postreinforcement pause (PRP), shown in left panels, and running rates (i.e., response rates calculated by excluding the postreinforcement pauses), in right panels, for the children in each group as a function of schedule value. Data are from the last three session on each FI value.

groups, the pauses of the five subjects who exhibited the low-rate pattern (IP, LR, MK, LC, and HP) generally increased as a function of schedule value but their duration was often as long as, or longer than, the FI requirement. The pauses of the one subject who showed the high-rate pattern (SR) were DISCUSSION short and did not alter with changes in Within the context of animal Fl perforschedule value. In the case of the three the scalloped pattern appears to be a mance, children in the 2 Y/2 to 4-year-old group, phenomenon (Dews, 1978; truly general pauses were also not very long and did not Lowe & Harzem, 1977; Richelle & Lejeune, show any consistent relationship with the The findings show, however, present 1979). schedule parameter. By way of contrast with of behavior on FI that there is no one pattern the data from other groups, the mean pauses

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Fig. 9. Duration of postreinforcement pause (Y) plotted as a function of fixed-interval value (X) on logarithmic coordinates for a group of four rats, four pigeons, and the four infants who participated in the present study. The power function and coefficient of determination are given for each group. (See text for further details.)

schedules that is typical of all human subjects. The response pattern of preverbal infants is scalloped and resembles that of animals, but by the age of 2 Y2 to 4 years, new and very irregular patterns predominate. This appears to mark a transitional stage between animal and human adult-like behavior; by the age of 5 years the irregular pattern gives way to either the high-rate or low-rate responding typical of adults (see also Long et al., 1958; DeCasper & Zeiler, 1972; Zeiler & Kelley, 1969). It is not only the FI scallop that disappears early in the child's life but also the sensitivity to changes in schedule value that characterizes both animal and infant responding. The low-rate pattern of behavior shown by some of the older children may be sensitive to schedule value insofar as only one or two responses are emitted per reinforcer, but this is a very different kind of sensitivity from that displayed by animals and infants; the behavior of humans who show the high-rate pattern seems to be almost entirely insensitive to FI duration (see also Leander et al., 1968; Weiner, 1969). The present study arose out of our earlier research on animal and human behavior. In a review of the literature, Lowe (1979) described some of the ways in which adult human schedule performance differs from that of other animal species; this applies to response patterning, sensitivity to schedule parameters, and the effects of reinforcement

history. On the basis of this evidence and additional experimental studies concerned with attenuating human subjects' covert verbal behavior by means of either concurrent verbal shadowing tasks (Lowe, 1979; see also Laties & Weiss, 1963; Sokolov, 1972) or the provision of a response-produced clock (Lowe, Harzem, & Bagshaw, 1978; Lowe, Harzem, & Hughes, 1978), Lowe concluded that the principal factor responsible for differences between human and animal schedule performance might be the role of verbal behavior in humans. When, for example, humans learn to formulate rules based upon verbal descriptions of their environment, then responding may no longer be a direct function of reinforcement but may also be governed by rules of the subjects' own devising. The acquisition of such verbal behavior is, of course, itself a function of reinforcement contingencies and there is little reason to doubt that the development of rule-governed behavior and its maintenance are also dependent upon reinforcement. Animal behavior, on the other hand, is directly governed by environmental contingencies and is free of sources of control arising from the development of language (cf. Skinner, 1966, 1974). According to this analysis, the behavior of young infants, like that of ahimals, should be directly contingency-controlled and consequently should show schedule effects that are characteristic of animal behavior. This prediction is confirmed by the present study.

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A second prediction, also confirmed, was that older children, who are capable of framing verbal descriptions of the schedule and rules for responding, should show rulegoverned behavior similar to that of adults. The results revealed that the children of 5 years and older produced verbal descriptions of the contingencies that were very similar to those of adults. Typically, adult subjects describe the Fl schedule either as one requiring many responses to be emitted for reward or as one where an interval of time has to elapse between the delivery of rewards. Adults who produce the low-rate pattern usually report that they had a time-based hypothesis and so counted out the interval before responding, whereas those who produce the high-rate pattern usually report the response-based formulation (Leander et al., 1968; Lippman & Meyer, 1967). Similar descriptions of the contingencies, with correlated patterns of high-rate and low-rate responding, were given by the two oldest groups of subjects in this experiment. In addition to voicing the low-rate hypothesis at the end of the study, some of the children (IP, LC, and HP) were heard to count out the interval during some of the early sessions. Such counting was invariably accompanied by a low-rate pattern of responding that persisted for the remainder of the ex-

periment. Although the response patterns of the two oldest groups of children and the infants were as predicted, the performance of the 2 /2 to 4-year-olds was not. But their behavior is entirely consistent with the present account. These children had some verbal behavior that may have interacted with their responding and disrupted the scalloped pattern, but they showed no evidence of formulating the kinds of description of the contingencies and rules for responding that were produced by the older children. Instead, the apparently unsystematic and varied verbalizations of these children were accompanied by varied and irregular response patterning. These findings are in close agreement with those of Vygotsky (1962, 1978) and Luria (1961, 1981), who have described in

some detail the ways in which conditioning relationships, shared by human infants and animals, are altered when the child learns to verbally describe stimulus events. They, too, have reported that before the age of 4 to 5 years children's capacity to use language to control their behavior is limited. Age, of course, is not the critical variable in their account; they have attempted to show in a number of studies that the development of verbal control is dependent upon appropriate learning conditions within a verbal community. The present results are also consistent with a number of studies that have demonstrated the effects of what children say upon what they do (e.g., Israel & O'Leary, 1973; Paniagua & Baer, 1982; Risley, 1977). Several experiments have shown that when children are instructed to describe how they will behave or how they have behaved, with reinforcers being presented only when their verbal reports correspond to their nonverbal behavior, the incidence of these reports and the behavior to which they refer greatly increases. Catania, Matthews, and Shimoff (1982) have demonstrated similar correspondences between verbal and nonverbal behavior in adults. With respect to the central importance assigned to verbal behavior in the development of rule-governed behavior and "consciousness" in humans, the theoretical system of Vygotsky and Luria is very similar to that of Skinner (1945, 1957, 1963, 1974). It is, therefore, a surprising feature of research conducted in the Skinnerian tradition that it has, to a great extent, ignored the development of language and its effect on behavioral relationships. Indeed the possibility that there might be major developmental differences in human operant responding does not appear to have been seriously considered (but see Bijou, 1976). One of the present authors has suggested elsewhere (Lowe, 1983) that this is in large part due to an excessive reliance by many researchers upon an animal model of human functioning and an exclusive concern with overt "observable" behavior, which has led to the avoidance, if not rejection, of accounts of human perfor-

DEVELOPMENTAL DIFFERENCES IN HUMAN PERFORMANCE mance that make inferences about covert behavior (e.g., see Baron & Galizio, 1983; Baron & Perone, 1982; Branch & Malagodi, 1980; Weiner, 1983). That reference to covert behavior should be considered suspect, in principle, is indeed a strange irony inasmuch as Skinner established the identity of radical, as opposed to methodological, behaviorism largely on the basis of its recognition of the importance of covert events in human behavior (Skinner, 1945, 1957, 1963, 1966, 1974). For example, in defining rule-governed behavior, a key concept in contemporary behavior analysis, Skinner (1966) described how an individual constructs his own rules, and may do so overtly or covertly: "Any actual formulation of the relation between a response and its consequences (perhaps simply the observation 'Whenever I respond in this way such and such an event follows') may, of course, function as a prior controlling stimulus" (p. 243). Similarly, Bijou, who has contributed much to the study of child behavior, has shown how the analysis of covert events is both consistent with behaviorist theory and is a practical necessity in dealing with problemsolving behavior in children (Bijou, 1976, pp. 70-74; Bijou & Baer, 1967). Of course, each researcher is free to choose his/her own research strategy, which may or may not embrace an analysis of the role of covert behavior, but it should be clearly recognized that the radical behaviorist thesis, as articulated by Skinner, does not eschew consideration of such events but, rather, maintains that it is folly for science to ignore them (and see Lowe, 1983, 1984). It may be possible to have other interpretations of the age-related differences in behavior reported here and in other studies (e.g., Bem, 1967; Luria, 1961; Vygotsky, 1962), although, apart from accounts framed in terms of "cognitive" constructs, it is not clear, at present, what they might be. The analysis described here has the merit of providing the basis for a coherent interpretation of most of the phenomena of human operant behavior recorded to date; it is also open to experimental test. It should be possible, for

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example, to determine whether the stages of operant development that we have described can be accelerated by providing children with appropriate verbal instructions and selfinstructions (see Lowe, 1983). Longitudinal studies of individual children, particularly covering the transitional period between 2 and 5 years old, should also be conducted. In addition, it would be of great benefit if an effective method were developed for the detailed analysis of young children's speech and its functional relationships with other operant behavior (cf. Zivin, 1979). We believe that such studies as these, together with related research on adult human performance (e.g., Catania et al., 1982; Lowe & Horne, in press; Matthews et al., 1977), will help to point the way to new directions for fundamental research and applied analysis (cf. Lowe & Higson, 1981, 1983; Zettle & Hayes, 1982).

REFERENCES Baron, A., & Galizio, M. (1983). Instructional control of human operant behavior. Psychological Record, 33, 495-520. Baron, A., & Perone, M. (1982). The place of the human subject in the operant laboratory. Behavior Analyst, 5, 142-158. Bem, S. L. (1967). Verbal self-control: The establishment of effective self-instruction. Journal of Experimental Psychology, 74, 485-491. Bijou, S. W. (1976). Child development: The basic stage of early childhood. Englewood Cliffs, NJ: Prentice-Hall. Bijou, S. W., & Baer, D. M. (1967). Child development: Readings in experimental analysis. New York: Appleton-Century-Crofts. Branch, M. N., & Malagodi, E. F. (1980). Where have all the behaviorists gone? Behavior Analyst, 3(1), 31-38. Catania, A. C. (1970). Reinforcement schedules and psycho-physical judgments. In W. N. Schoenfeld (Ed.), The theory of reinforcement schedules (pp. 1-42). New York: Appleton-Century-Crofts. Catania, A. C., Matthews, B. A., & Shimoff, E. (1982). Instructed versus shaped human verbal behavior: Interactions with nonverbal responding. Journal of the Experimental Analysis of Behavior, 38, 233-248. DeCasper, A. J., & Zeiler, M. D. (1972). Steadystate behavior in children: A method and some data. Journal of Experimental Child Psychology, 13, 231-239. Dews, P. B. (1978). Studies on responding under fixed-interval schedules of reinforcement: II. The scalloped pattern of the cumulative record. Journal of the Experimental Analysis of Behavior, 29, 67-75.

180

R. P. BENTALL et al.

Hanson, H. M., Campbell, E. H. & Witoslawski, J. J. (1962). FI length and performance on an FI FR chain schedule of reinforcement. Journal of the Experimental Analysis of Behavior, 5, 331-333. Hanson, S. J., & Killeen, P. R. (1981). Measurement and modeling of behavior under fixedinterval schedules of reinforcement. Journal of Experimental Psychology: Animal Behavior Processes, 7, 129-139. Israel, A. C., & O'Leary, K. D. (1973). Developing correspondence between children's words and deeds. Child Development, 44, 575-581. Laties, V. G., & Weiss, B. (1963). Effects of a concurrent task on fixed-interval responding in humans. Journal of the Experimental Analysis of Behavior, 6, 431-436. Leander, J. D., Lippman, L. G., & Meyer, M. E. (1968). Fixed interval performance as related to subjects' verbalizations of the reinforcement contingency. Psychological Record, 18, 469-474. Lippman, L. G., & Meyer, M. E. (1967). Fixed interval performance as related to instructions and to subjects' verbalizations of the contingency. Psychonomic Science, 8, 135-136. Long, E. R., Hammack, J. T., May, F., & Campbell, B. J. (1958). Intermittent reinforcement of operant behavior in children. Journal of the Experimental Analysis of Behavior, 1, 315-339. Lowe, C. F. (1979). Determinants of human operant behaviour. In M. D. Zeiler & P. Harzem (Eds.), Advances in analysis of behaviour: Vol. 1. Reinforcement and the organization of behaviour (pp. 159-192). Chichester, England: Wiley. Lowe, C. F. (1983). Radical behaviorism and human psychology. In G. C. L. Davey (Ed.), Animal models of human behavior: Conceptual, evolutionary and neurobiological perspectives (pp. 71-93). Chichester, England: Wiley. Lowe, C. F. (1984). The flight from human behaviour. Behavioral and Brain Sciences, 7, 562-563. Lowe, C. F., Beasty, A., & Bentall, R. P. (1983). The role of verbal behavior in human learning: Infant performance on fixed-interval schedules. Journal of the Experimental Analysis of Behavior, 39, 157-164. Lowe, C. F., & Harzem, P. (1977). Species differences in temporal control of behavior. Journal of the Experimental Analysis of Behavior, 28, 189-201. Lowe, C. F., Harzem, P., & Bagshaw, M. (1978). Species differences in temporal control of behavior II: Human performance. Journal of the Experimental Analysis of Behavior, 29, 351-361. Lowe, C. F., Harzem, P., & Hughes, S. (1978). Determinants of operant behaviour in humans: Some differences from animals. Quarterly Journal of Experimental Psychology, 30, 373-386. Lowe, C. F., Harzem, P., & Spencer, P. T. (1979). Temporal control of behavior and the power law. Journal of the Experimental Analysis of Behavior, 31, 333-343. Lowe, C. F., & Higson, P. J. (1981). Selfinstructional training and cognitive behaviour modification: A behavioural analysis. In G. Davey (Ed.), Applications of conditioning theory (pp. 162-188). London: Methuen.

Lowe, C. F., & Higson, P. J. (1983). Is all behaviour modification 'cognitive'? In E. Karang (Ed.), Current issues in clinical psychology (pp. 207-227). London: Plenum Press. Lowe, C. F., & Horne, P. J. (in press). On the, generality of behavioural principles: Human choice and the matching law. In C. F. Lowe, M. Richelle, D. E. Blackman, & C. M. Bradshaw (Eds.), Behaviour analysis and contemporary psychology. London: Erlbaum. Lowe, C. F., & Wearden, J. H. (1981). A quantitative model of temporal control on fixed-interval schedules: Dynamic properties of behaviour. In C. M. Bradshaw, E. Szabadi, & C. F. Lowe (Eds.), Quantification of steady-state operant behaviour (pp. 177-188). Amsterdam: Elsevier/North Holland Biomedical Press. Luria, A. R. (1961). The role of speech in the regulation of nornal and abnormal behavior. New York: Liveright. Luria, A. R. (1981). Language and cognition (J. V. Wertsch, Ed.). New York: Wiley. Matthews, B. A., Shimoff, E., Catania, A. C., & Sagvolden, T. (1977). Uninstructed human responding: Sensitivity to ratio and interval contingencies. Journal of the Experimental Analysis of Behavior, 27, 453-467. Paniagua, F. A., & Baer, D. M. (1982). The analysis of correspondence training as a chain reinforceable at any point. Child Development, 53, 786-798. Reynell, J. K. (1977). The Reynell developmental language scale (rev. ed.). London: N. F. E. R. Richelle, M., & Lejeune, H. (1979). Time in animal behaviour. Oxford: Pergamon Press. Risley, T. R. (1977). The social context of selfcontrol. In R. B. Stuart (Ed.), Behavioral selfmanagement: Strategies, techniques and outcomes (pp. 71-81). New York: Brunner/Mazel. Skinner, B. F. (1938). The behavior of organisms. New York: Appleton-Century-Crofts. Skinner, B. F. (1945). The operational analysis of psychological terms. Psychological Review, 52,

270-277. Skinner, B. F. (1957). Verbal behavior. New York: Appleton-Century-Crofts. Skinner, B. F. (1963). Behaviorism at fifty. Science, 140, 951-958.

Skinner, B. F. (1966). An operant analysis of problem solving. In B. Kleinmuntz (Ed.), Problem solving: Research, method and theory (pp. 225-257). New York: Wiley. Skinner, B. F. (1974). About behaviorism. New York: Knopf. Sokolov, A. N. (1972). Inner speech and thought (G. T. Onischenko, Trans.). New York: Plenum Press. Starr, B. C., & Staddon, J. E. R. (1974). Temporal control on periodic schedules: Signal properties of reinforcement and blackout. Journal of the Experimental Analysis of Behavior, 22, 535-545. Vygotsky, L. S. (1962). Thought and language (E. Hanfmann & G. Vakar, Ed. & Trans.) Cambridge, MA: MIT Press. Vygotsky, L. S. (1978). Mind in society: The development of higher psychological processes (M. Cole, V. John-Steiner, S. Scribner, & E. Souberman, Eds.). Cambridge, MA: Harvard University Press.

DEVELOPMENTAL DIFFERENCES IN HUMAN PERFORMANCE

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tion. Journal of Experimental Child Psychology, 8, Weiner, H. (1969). Controlling human fixed306-313. interval performance. Journal of the Experimental Zettle, R. D., & Hayes, S. C. (1982). RuleAnalysis of Behavior, 12, 349-373. governed behavior: A potential theoretical Weiner, H. (1983). Some thoughts on discrepant framework for cognitive behavior therapy. In P. C. human-animal performances under schedules of Kendall (Ed.), Advances in cognitive-behavioral research reinforcement. Psychological Record, 33, 521-532. and therapy (Vol. 1, pp. 76-118). New York: Wilson, M. P. (1954). Periodic reinforcement interAcademic Press. val and number of periodic reinforcements as parameters of response strength. Journal of Com- Zivin, G. (Ed.). (1979). The development of selfregulation through private speech. New York: Wiley. parative and Physiological Psychology, 47, 51-56. Zeiler, M. D., & Kelley, C. A. (1969). Fixed-ratio Received March 23, 1984 and fixed-interval schedules of cartoon presentaFinal acceptance November 27, 1984