Discrimination theory of rule-governed behavior

Effects of reinforcement and response-cost history on instructional control

The present study compared the effects of reinforcement or punishment versus no additional consequences for instruction following on instructional control and subsequent rule-governed insensitivity. In two experiments, adult participants were presented with repeated choices between a short progressive-time schedule and either a fixed time-schedule or a longer progressive-time schedule. In Experiment 1, three groups were given an initially accurate instruction relative to the direct contingency. A control group experienced no additional consequences for compliance with instructions, whereas compliance resulted in additional points for a second group, and noncompliance led to the subtraction of points for a third group. In a subsequent phase, instructions became inaccurate and there were no additional consequences for compliance or noncompliance for any group. Consistent with previous results, rule-governed insensitivity was observed in all participants. Experiment 2 employed the same procedure, except instructions were inaccurate throughout all sessions, and compliance in the subsequent phase resulted in diminishing points per session. Reinforcement for following instructions increased instructional control and subsequent rule-governed insensitivity. This increase was maintained even after the termination of additional consequences, a result that supports theoretical suggestions that a history of reinforcement for complying with instructions and rules is an important factor in rule-governed insensitivity.

Empirical Evaluations of Skinner's Analysis of Problem Solving

We reviewed 12 studies in which the researcher taught problem-solving strategies, such as self-questioning and visual imagining, to children and adolescents with and without disabilities to facilitate the learning of math, spelling, play/social, and communication skills. We analyzed these studies in terms of types of problem-solving strategies, the multiple control involved in problem solving, the extent to which problem solving occurred at the overt or covert level. In addition to suggesting limitations of the literature, we recommend areas for future research and practice.

Dynamic probability of reinforcement for cooperation: Random game termination in the centipede game

Experimental games have previously been used to study principles of human interaction. Many such games are characterized by iterated or repeated designs that model dynamic relationships, including reciprocal cooperation. To enable the study of infinite game repetitions and to avoid endgame effects of lower cooperation toward the final game round, investigators have introduced random termination rules. This study extends previous research that has focused narrowly on repeated Prisoner's Dilemma games by conducting a controlled experiment of two-player, random termination Centipede games involving probabilistic reinforcement and characterized by the longest decision sequences reported in the empirical literature to date (24 decision nodes). Specifically, we assessed mean exit points and cooperation rates, and compared the effects of four different termination rules: no random game termination, random game termination with constant termination probability, random game termination with increasing termination probability, and random game termination with decreasing termination probability. We found that although mean exit points were lower for games with shorter expected game lengths, the subjects' cooperativeness was significantly reduced only in the most extreme condition with decreasing computer termination probability and an expected game length of two decision nodes.

A Functional Analysis of Psychological Terms Redux

In his seminal paper, "An Operational Analysis of Psychological Terms," Skinner (1945) offered the revolutionary suggestion that, rather than endlessly debating the meanings of psychological terms, psychologists should analyze the variables that control their occurrence as verbal behavior. Skinner's suggestion reflected the essence of his 1957 book, Verbal Behavior, wherein he argued that the behaviors of which language is composed (i.e., speaking and listening) are controlled by variables found in the social environment (which he called the verbal community), and that analyzing those variables would lead to an understanding of the behaviors. Although Skinner formally introduced his radical approach to language in 1945, it has yet to be fully realized. The result is that psychologists, including behavior analysts, still debate the definitions of terms. In the present paper, I review Skinner's functional approach to language and describe ways in which behavior analysts have already applied it to traditional psychological terms. I conclude by looking at other current terms in behavior analysis that engender some confusion and encourage behavior analysts to apply a functional analytic approach to their own verbal behavior.

A Systematic Review of Pliance, Tracking, and Augmenting

Within relational frame theory, a distinction has been made between three types of rule-governed behavior known as pliance, tracking, and augmenting. This review examined whether there is support for the concepts of pliance, tracking, and augmenting in the experimental analysis of behavior; whether these concepts refer to distinct functional classes of behavior; and how these concepts have been operationalized in experimental (behavioral-analytic) research. Given that the concepts of pliance, tracking, and augmenting were first defined by Zettle and Hayes, we confined our review to studies published in or after 1982. Our results indicate that (a) experimental research investigating pliance, tracking, and/or augmenting is extremely limited; (b) it is difficult to determine the extent to which the concepts of pliance, tracking, and augmenting allow for relatively precise experimental analyses of distinct functional classes of behavior; and (c) pliance and tracking have been operationalized by using a limited set of procedures.

Efeitos da História Comportamental e de Instruções sobre a Aquisição e a Resistência à Extinção em um Esquema Múltiplo FR DRL

RESUMOPara verificar os efeitos da história comportamental e de instruções sobre a aquisição e a resistência à extinção, 15 universitários foram distribuídos em três grupos. Na Fase 1, o Grupo 1 foi exposto a aumentos graduais nos valores dos componentes até um múltiplo FR 60 DRL 20 s; os grupos 2 e 3 foram expostos diretamente a esse esquema, mas o Grupo 3 recebeu instruções. Na Fase 2, o FR foi ajustado e um múltiplo FR n DRL 20 s foi mantido até a estabilidade. Na Fase 3 estava em vigor um múltiplo Extinção Extinção. As instruções, em comparação com a exposição gradual ou direta aos esquemas, facilitaram a aquisição de taxas diferenciadas de respostas, mas aumentaram a resistência à extinção.

Reprint of "Mathematics as verbal behavior"

"Behavior which is effective only through the mediation of other persons has so many distinguishing dynamic and topographical properties that a special treatment is justified and indeed demanded" (Skinner, 1957, p. 2). Skinner's demand for a special treatment of verbal behavior can be extended within that field to domains such as music, poetry, drama, and the topic of this paper: mathematics. For centuries, mathematics has been of special concern to philosophers who have continually argued to the present day about what some deem its "special nature." Two interrelated principal questions have been: (1) Are the subjects of mathematical interest pre-existing in some transcendental realm and thus are "discovered" as one might discover a new planet; and (2) Why is mathematics so effective in the practices of science and engineering even though originally such mathematics was "pure" with applications neither contemplated or even desired? I argue that considering the actual practice of mathematics in its history and in the context of acquired verbal behavior one can address at least some of its apparent mysteries. To this end, I discuss some of the structural and functional features of mathematics including verbal operants, rule-and contingency-modulated behavior, relational frames, the shaping of abstraction, and the development of intuition. How is it possible to understand Nature by properly talking about it? Essentially, it is because nature taught us how to talk.

Mathematics as verbal behavior

"Behavior which is effective only through the mediation of other persons has so many distinguishing dynamic and topographical properties that a special treatment is justified and indeed demanded" (Skinner, 1957, p. 2). Skinner's demand for a special treatment of verbal behavior can be extended within that field to domains such as music, poetry, drama, and the topic of this paper: mathematics. For centuries, mathematics has been of special concern to philosophers who have continually argued to the present day about what some deem its "special nature." Two interrelated principal questions have been: (1) Are the subjects of mathematical interest pre-existing in some transcendental realm and thus are "discovered" as one might discover a new planet; and (2) Why is mathematics so effective in the practices of science and engineering even though originally such mathematics was "pure" with applications neither contemplated or even desired? I argue that considering the actual practice of mathematics in its history and in the context of acquired verbal behavior one can address at least some of its apparent mysteries. To this end, I discuss some of the structural and functional features of mathematics including verbal operants, rule-and contingency-modulated behavior, relational frames, the shaping of abstraction, and the development of intuition. How is it possible to understand Nature by properly talking about it? Essentially, it is because nature taught us how to talk.

Efeitos de perguntas e de respostas às perguntas sobre o seguir regras apresentadas em uma história infantil

O estudo investigou os efeitos de perguntas e respostas às perguntas sobre o seguir regras por 15 crianças, distribuídas em três grupos. Nas fases 1 e 3 era medido o comportamento de doar bombons e na Fase 2 era contada uma história com uma regra especificando que quem doa alimentos tem amigos para brincar. Os grupos diferiram na Fase 2: para o Grupo 1 não eram feitas perguntas; para o Grupo 2 eram feitas perguntas ao longo da história; e para o Grupo 3 eram feitas perguntas ao final da história. Dos participantes que não doaram bombons na Fase 1 dos grupos 1, 2 e 3, 50%, 100% e 100%, respectivamente, doaram na Fase 3. Sugere-se que perguntas e respostas podem interferir na ocorrência do seguir regras.

The role of atomic repertoires in complex behavior

Evolution and reinforcement shape adaptive forms and adaptive behavior through many cycles of blind variation and selection, and therein lie their parsimony and power. Human behavior is distinctive in that this shaping process is commonly "short circuited": Critical variations are induced in a single trial. The processes by which this economy is accomplished have a common feature: They all exploit one or more atomic repertoires, elementary units of behavior each under control of a distinctive stimulus. By appropriate arrangements of these discriminative stimuli, an indefinite number of permutations of atomic units can be evoked. When such a permutation satisfies a second contingency, it can come under control of the relevant context, and the explicit arrangement of discriminative stimuli will no longer be required. Consequently, innovations in adaptive behavior can spread rapidly through the population. A consideration of atomic repertoires informs our interpretation of generalized operants and other phenomena that are otherwise difficult to explain. Observational learning is discussed as a case in point.

Evocative and function-altering effects of contingency-specifiying stimuli

This study examined the effects of various forms of contingency-specifying stimuli (CSSs) on the compliance of 4-year-old children, and attempted to separate the evocative vs. function-altering functions of the CSSs. Each child was presented with a series of CSSs (one per day) that differed with respect to the deadline specified (immediate or delayed) and the consequence specified for performing the task. In the second part of the experiment, the CSSs either specified a delayed deadline or did not specify a deadline. Also, the consequences that were specified were either immediate or delayed. The results showed that under conditions where the opportunity to respond was immediately available, (a) CSSs that specified deadlines and immediate consequences exerted reliable control over behavior, and (b) deadlines, whether delayed or immediate exerted some control over the behavior, even when CSSs specified no consequences for task completion. Under conditions where the opportunity to respond was delayed, (a) CSSs of any kind were less likely to exert reliable control, and (b) children were most likely to respond when CSSs specified immediate consequences and made no mention of a deadline. Results are interpreted in terms of the role of CSSs as evocative and/or function-altering and in terms of deadlines as learned aversive conditions.

A reply to behavior analysts writing about rules and rule-governed behavior

Verbal stimuli called "rules" or "instructions" continue to be interpreted as discriminative stimuli despite recent arguments against this practice. Instead, it might more fruitful for behavior analysts to focus on "contingency-specifying stimuli" which are function-altering. Moreover, rather than having a special term, "rule," for verbal stimuli whose only function is discriminative, perhaps behavior analysts should reserve the term, if at all, only for these function-altering contingency-specifying stimuli.

The trouble with babies and the value of bathwater: Complexities in the use of verbal reports as data

Recent interest among behavior analysts in protocol analysis techniques prompts a consideration of some general measurement issues and some special issues relevant to protocol analysis. The development of behavior- analytic method and theory specific to verbal report research is a good thing, and Ericsson and Simon's (1984) book, Protocol Analysis, provides a useful model of integrating psychological theory and the craft of research. But protocol analysis techniques do not provide a magic window to the "world within the skin," and individual researchers should adopt these techniques only after confronting thorny issues such as how to determine the operating characteristics of verbal reports about private events, how to identify public performances to which protocol analysis can be applied productively, and how to maintain theoretical integrity in the empirical search for private events. We also caution against letting enthusiasm (and controversy) regarding protocol analysis distract behavior analysts from the benefits of using verbal report methods to study interesting events that are public in principle but difficult to measure in practice.

A descriptive analysis of family discussions about everyday problems and decisions

Skinner's Verbal Behavior (1957) and "An operant analysis of problem solving" (1966) were used to develop a coding system to analyze the relationships between verbal behaviors in family problem solving discussions. Taking solution statements as a target behavior, sequential relationships were examined with both subsequent and antecedent verbal behaviors, comparing families with higher and lower rates of solution statements. Results indicated that two categories of verbal behavior occurred both subsequent and antecedent to solution statements more frequently in families with higher frequencies of solution statements: Agreements and contingency statements. Results are discussed in terms of an operant theory of problem solving in which agreements may serve as reinforcers for solutions and contingency statements may serve as discriminative stimuli.

Defining terms in behavior analysis: Reinforcer and discriminative stimulus

Many definitions of reinforcer and discriminative stimulus found in behavioral texts include a requirement of temporal proximity between stimulus and response. However, this requirement is not consistently adopted. We present additional evidence from a questionnaire that was sent to members of the editorial boards of several behavioral journals showing that there is not universal agreement concerning the temporal parameters accepted in the definitions of reinforcer and discriminative stimulus. We suggest that the disagreement over the definitions of these essential terms ought to be at least addressed if not resolved. Because the discrepancy usually occurs when the behavior of verbal humans is at issue, we urge behavior analysts to be conservative when extending the terms reinforcer and discriminative stimulus from the behavior of nonhumans in the laboratory to human behavior where the effects of many stimuli may depend in part on sophisticated verbal repertoires.

Making sense of sensitivity in the human operant literature

Human operant behavior is often said to be controlled by different variables or governed by different processes than nonhuman operant behavior. Support for this claim within the operant literature comes from data suggesting that human behavior is often insensitive to schedules of reinforcement to which nonhuman behavior has been sensitive. The data that evoke the use of the terms sensitivity and insensitivity, however, result from both between-species and within-subject comparisons. We argue that because sensitivity is synonymous with experimental control, conclusions about sensitivity are best demonstrated through within-subject comparisons. Further, we argue that even when sensitivity is assessed using within-subject comparisons of performance on different schedules of reinforcement, procedural differences between studies of different species may affect schedule performance in important ways. We extend this argument to age differences as well. We conclude that differences across populations are an occasion for more precise experimental analyses and that it is premature to conclude that human behavior is controlled by different processes than nonhuman behavior.

Some reflections on 25 years of the association for behavior analysis: Past, present, and future

This paper offers some reflections on the discipline and profession of behavior analysis, as well as on the Association for Behavior Analysis (ABA), on the occasion of the association's 25th anniversary. It is based on a panel session conducted at the 1999 convention that included six past presidents of ABA (Donald M. Baer, Judith E. Favell, Sigrid S. Glenn, Philip N. Hineline, Jack Michael, and Edward K. Morris) and its current Executive Director and Secretary-Treasurer (Maria E. Malott). Among the topics addressed were (a) the survival of behavior analysis in university and cultural contexts, (b) the training of behavior-analytic researchers and practitioners, (c) relations between basic and applied research, (d) convergences between behavior analysis and other disciplines, (e) the structure and function of ABA, and (f) the importance of students for the future of the association, the discipline, and the profession. Questions from the audience raised issues concerning the relevance of major behavior-analytic journals, advances in behavior analysis since the death of B. F. Skinner, and the availability of accessible, popular material on applied behavior analysis.

Separating discriminative and function-altering effects of verbal stimuli

Ever since Skinner's first discussion of rule-governed behavior, behavior analysts have continued to define rules, either explicitly or implicitly, as verbal discriminative stimuli. Consequently, it is not difficult to find, in the literature on rule-governed behavior, references to stimulus control, antecedent control, or to rules occasioning behavior. However, some verbal stimuli have effects on behavior that are not easily described as discriminative. Such stimuli don't evoke behavior as discriminative stimuli, but rather alter the functions of other stimuli in a manner analogous to operant and respondent conditioning. Hence, this type of control has been called function altering. Any known stimulus function (e.g., evocative, or [conditioned] reinforcing or punishing functions) can apparently be altered by such function-altering stimuli. Describing these stimuli as discriminative stimuli obscures their possible function-altering effects and consequently may retard inquiry into them. This paper encourages behavior analysts to begin separating the discriminative and function-altering effects of verbal stimuli and suggests that by doing so, behavior analysts may better understand what may be most unique about these stimuli. Results from several experiments, especially those in which children served as subjects, are analyzed. Finally, some speculations are offered concerning the genesis of function-altering stimuli.

Low interrater agreement on the semantic base of textual material

The present paper describes three experiments which were conducted to determine whether independent raters could agree upon the semantic base of textual materials. These experiments were occasioned by an earlier experiment in which the investigators reported success in increasing the ability of students to extract the semantic base from textual materials. The present paper reports our unsuccessful attempts to obtain an acceptable level of agreement among independent raters about what constituted the semantic base of a number of texts. The paper concludes by raising some doubts about the strategy of extending behavior-analytic research to verbal behavior by combining behavior-change procedures with cognitive constructs.

The dimensions of clinical behavior analysis

In most talk therapies for outpatient adults, the therapist has no contro over the client's daily life or contingencies outside the treatment session. The fundamental theoretical issue facing the behavior analyst is, "How can the talking that goes on during the session help the client with problems that occur outside the session in the client's daily life?" An historical analysis and the application of verbal behavior principles are used to answer the question and form the basis of clinical behavior analysis (CBA). The implications of CBA range from providing a theoretical base for psychotherapy to suggesting new forms of treatment.

Effects of grammar instruction and fluency training on the learning of the and a by native speakers of japanese

In a computer-assisted sentence completion task, the effects of grammar instruction and fluency training on learning the use of the definite and indefinite articles of English were examined. Forty-eight native Japanese-speaking students were assigned to four groups: with grammar/accuracy (G/A), without grammar/accuracy (N/A), with grammar/fluency (G/F), and without grammar/fluency (N/F). In the G/A and N/A groups, training continued until performance reached 100% accuracy (accuracy criterion). In the G/F and N/F groups, training continued until 100% accuracy was reached and the correct responses were made at a high speed (fluency criterion). Grammar instruction was given to participants in the G/A and G/F groups but not to those in the N/A and N/F groups. Generalization to new sentences was tested immediately after reaching the required criterion. High levels of generalization occurred, regardless of the type of mastery criterion and whether the grammar instruction was given. Retention tests were conducted 4, 6, and 8 weeks after training. Fluency training effectively improved retention of the performance attained without the grammar instruction. This effect was diminished when grammar instruction was given during training. Learning grammatical rules was not necessary for the generalized use of appropriate definite and indefinite articles or for the maintenance of the performance attained through fluency training.

A descriptive taxonomy of environmental operations and its implications for behavior analysis

Environmental operations may be classified according to whether they have evocative or function-altering effects. Evocative events, such as the presentation of unconditioned and conditioned stimuli, establishing operations, and discriminative stimuli, serve to increase, decrease, or maintain the momentary frequency of behavior. Function-altering operations, such as operant and respondent conditioning, the correlation of stimuli, and the presentation of certain verbal stimuli, serve to increase, decrease, or maintain the evocative and function-altering (e.g., reinforcing or punishing) functions of other events. This paper expands upon the functional taxonomy of environmental events described by Michael (1993a). The resulting classification scheme should permit behavior analysts to more easily respond to similarities and differences between functional environmental events. This paper discusses implications of the suggested taxonomy for how behavior analysts talk about motivational variables, discriminative stimuli, the operant unit of analysis, and the distinction between operant and respondent conditioning.

The effects of stating contingency-specifying stimuli on compliance in children

The present investigation examined whether distinguishing between the discriminative and function-altering properties of contingency-specifying stimuli (CSS) is of heuristic value in conceptualizing child compliance. Groups of "compliant" and "noncompliant" children were instructed to place several blocks in a box. During half of the trials the children had an immediate opportunity to respond to the instruction (IOR), and during the other trials the children's opportunity to respond was delayed by 10 min (DOR). Results showed that 5 of the 8 children were more likely to comply in the IOR condition, whereas the 3 remaining children were equally compliant in IOR and DOR conditions. In addition, the study investigated the influence of condition presentation sequence on child compliance. Thus, half of the children entered the IOR condition first, and the other half entered the DOR condition first. Results showed no differences in compliance for 3 of 4 children in the IOR-first sequence. However, in the DOR-first sequence, all children, regardless of classification, were more compliant in IOR than in DOR conditions. Presentation order appeared to strongly influence compliance and could likely have affected the results of prior investigations.

Evaluating theory-based evaluation: information, norms, and adherence

Programmatic social interventions attempt to produce appropriate social-norm-guided behavior in an open environment. A marriage of applicable psychological theory, appropriate program evaluation theory, and outcome of evaluations of specific social interventions assures the acquisition of cumulative theory and the production of successful social interventions--the marriage permits us to advance knowledge by making use of both success and failures. We briefly review well-established principles within the field of program evaluation, well-established processes involved in changing social norms and social-norm adherence, the outcome of several program evaluations focusing on smoking prevention, pro-environmental behavior, and rape prevention and, using the principle of learning from our failures, examine why these programs often do not perform as expected. Finally, we discuss the promise of learning from our collective experiences to develop a cumulative science of program evaluation and to improve the performance of extant and future interventions.

Sources cited most frequently in the experimental analysis of human behavior

We conducted an analysis of the sources cited most frequently in primary empirical reports in the experimental analysis of human behavior (EAHB) published in four journals between 1990 and 1999. Citation patterns suggest that modern EAHB is topically focused and relatively independent of both animal operant research and human research conducted outside of behavior analysis.

An analysis of concept learning: simple conceptual control and definition-based conceptual control

Concept learning can involve either contingency shaping of stimulus-class discriminations or the application of definitions of the concepts. Experimental behavior analysts have studied contingency shaping, whereas educational psychologists have studied definitional concept training. In this paper, we analyze definition-based concept learning in terms of stimulus-response chains. Then we apply this chaining analysis to principles of instruction proposed by educational psychologists. These principles include (a) stating the definition in terms of critical and variable attributes, (b) using examples and nonexamples, (c) using a rational set of examples and nonexamples, (d) presenting coordinate concepts simultaneously, and (e) presenting the next instance based on the learner's previous error.

Rules, culture, and fitness

Behavior analysis risks intellectual isolation unless it integrates its explanations with evolutionary theory. Rule-governed behavior is an example of a topic that requires an evolutionary perspective for a full understanding. A rule may be defined as a verbal discriminative stimulus produced by the behavior of a speaker under the stimulus control of a long-term contingency between the behavior and fitness. As a discriminative stimulus, the rule strengthens listener behavior that is reinforced in the short run by socially mediated contingencies, but which also enters into the long-term contingency that enhances the listener's fitness. The long-term contingency constitutes the global context for the speaker's giving the rule. When a rule is said to be "internalized," the listener's behavior has switched from short- to long-term control. The fitness-enhancing consequences of long-term contingencies are health, resources, relationships, or reproduction. This view ties rules both to evolutionary theory and to culture. Stating a rule is a cultural practice. The practice strengthens, with short-term reinforcement, behavior that usually enhances fitness in the long run. The practice evolves because of its effect on fitness. The standard definition of a rule as a verbal statement that points to a contingency fails to distinguish between a rule and a bargain ("If you'll do X, then I'll do Y"), which signifies only a single short-term contingency that provides mutual reinforcement for speaker and listener. In contrast, the giving and following of a rule ("Dress warmly; it's cold outside") can be understood only by reference also to a contingency providing long-term enhancement of the listener's fitness or the fitness of the listener's genes. Such a perspective may change the way both behavior analysts and evolutionary biologists think about rule-governed behavior.

Efeitos de manipulações de propriedades formais de estímulos verbais sobre o comportamento

Objetivando avaliar os efeitos de estímulos antecedentes verbais sobre o comportamento, 24 estudantes universitários foram expostos a um procedimento de escolha segundo o modelo; a tarefa consistia em apontar para cada um dos três estímulos de comparação. O comportamento correto era reforçado em razão fixa 6. Na Condição 1, a ordem de apresentação dos estímulos nas Fases 2, 3, 4 e 5 era: instrução correspondente, instrução mínima, pergunta correspondente, pergunta mínima, respectivamente. As oito condições diferiam quanto à ordem de apresentação das instruções e perguntas. A instrução e a pergunta correspondente estabeleceram o comportamento correto em 95% e 33% dos casos, respectivamente. A instrução e a pergunta mínima não estabeleceram o comportamento correto. Os resultados têm implicações para as definições de regras.

Instructional versus schedule control of humans' choices in situations of diminishing returns

Four adult humans chose repeatedly between a fixed-time schedule (of points later exchangeable for money) and a progressive-time schedule that began at 0 s and increased by a fixed number of seconds with each point delivered by that schedule. Each point delivered by the fixed-time schedule reset the requirements of the progressive-time schedule to its minimum value. Subjects were provided with instructions that specified a particular sequence of choices. Under the initial conditions, the instructions accurately specified the optimal choice sequence. Thus, control by instructions and optimal control by the programmed contingencies both supported the same performance. To distinguish the effects of instructions from schedule sensitivity, the correspondence between the instructed and optimal choice patterns was gradually altered across conditions by varying the step size of the progressive-time schedule while maintaining the same instructions. Step size was manipulated, typically in 1-s units, first in an ascending and then in a descending sequence of conditions. Instructions quickly established control in all 4 subjects but, by narrowing the range of choice patterns, they reduced subsequent sensitivity to schedule changes. Instructional control was maintained across the ascending sequence of progressive-time values for each subject, but eventually diminished, giving way to more schedule-appropriate patterns. The transition from instruction-appropriate to schedule-appropriate behavior was characterized by an increase in the variability of choice patterns and local increases in point density. On the descending sequence of progressive-time values, behavior appeared to be schedule sensitive, sometimes even optimally sensitive, but it did not always change systematically with the contingencies, suggesting the involvement of other factors.