Pigeons' preference for free choice: number of keys versus key area.

In concurrent-chains schedules, pigeons prefer terminal links that provide two keys correlated with reinforcers (free choice) over those that provide only one key (forced choice), terminal-link reinforcement rates being equal. With same-size keys, free choice provides a larger area available for pecking. Preferences were examined using terminal links that differed in key number only (one or two) or key size only (small and medium or medium and large), or that equated the area of the two free-choice keys with that of the forced-choice key. Medium (standard) keys were typically preferred to small keys, but indifference was typically obtained between medium and large keys. The size preference usually overrode free-choice preference with one medium key pitted against two small keys, but free-choice preference was reliably observed with one large key pitted against two medium keys. In other words, preferences were a joint function of key number and key area, implying that free-choice preference is not reducible to preference for larger key areas. Free-choice preference requires separate keys rather than larger areas; the relevant behavioral units are the discriminated operants correlated with each terminal-link key rather than classes defined by topographical features such as area or perimeter.

Higher-order behavior classes: contingencies, beliefs, and verbal behavior.

The concepts of reinforcement and of higher-order classes of behavior are reviewed and applied to analyses of self-reinforcement, self-efficacy, the causal status of private events, and the role of verbal behavior in human action. The analyses support the case that Bandura's criticisms of behavior analytic thought rest upon several misunderstandings, the most important of which are the distinctions between theories and phenomena and a neglect of the process of ontogenic selection. Bandura's persistence in promoting these misunderstandings is puzzling, because over a period of at least two decades he has repeated without substantial correction arguments that were refuted at the time he first made them. Bandura's views on these concepts can be interpreted as a contemporary variety of creationism in behavioral science.

Using computers to teach behavior analysis.

When it is impractical to provide behavior analysis students with extensive laboratory experience using real organisms, computers can provide effective demonstrations, simulations, and experiments. Furthermore, such computer programs can establish contingency-shaped behavior even in lecture classes, which usually are limited to establishing rule-governed behavior. We describe the development of computerized shaping simulations and the development of software that teaches students to discriminate among reinforcement schedules on the basis of cumulative records.

B. F. Skinner, organism.

B. F. Skinner illustrated the power of behavior analysis by turning it upon his own behavior. This article considers parallels in the life and work of Charles Darwin and places Skinner's views on life and death in the context of his selectionist paradigm for psychology. The term organism plays a special role, and the account shows why B. F. Skinner might have regarded it as an appropriate title.

The gifts of culture and of eloquence: An open letter to Michael J. Mahoney in reply to his article, "Scientific psychology and radical behaviorism".

In what seems to be a response to a paper by Skinner (1987), Mahoney (1989) provides evidence of unfamiliarity with and intellectual intolerance toward radical behaviorism by presenting a critique of it that includes a variety of improper and counterfactual attributions. For example, he argues that radical behaviorism is Cartesian rather than Baconian when the historical record shows the opposite, that it is fundamentally associationist when in fact it is selectionist, and that its philosophy of science is essentially that of operationalism and logical positivism when instead it moved on to other criteria decades ago. The details of Mahoney's history are sometimes flawed and sometimes unsubstantiated, as when he provides a distorted account of the origins of the Association for Behavior Analysis or when he makes undocumented claims about the banning of books. On examination, many of his arguments are couched in stylistic terms that share their rhetorical features with racial, ethnic, and religious stereotyping.

Nonverbal behavior correlated with the shaped verbal behavior of children.

Children under 6 years old pressed on response windows behind which stimuli appeared (star or tree). Presses occasionally lit lamps arranged in a column; a present was delivered when all lamps were lit. A random-ratio schedule in the presence of star alternated with a random-interval schedule in the presence of tree. These contingencies usually did not produce respective high and low response rates in the presence of star and tree, but the shaping of verbal behavior (e.g., "press a lot without stopping" or "press and wait") was sometimes accompanied by corresponding changes in response rate. Verbal shaping was accomplished between schedule components during verbal interactions between the child and a hand-puppet, Garfield the Cat, and used social consequences such as enthusiastic reactions to what the child had said as well as concrete consequences such as delivery of extra presents. Variables that may constrain the shaping of verbal behavior in children seem to include the vocabulary available to the child and the functional properties of that vocabulary; the correlation between rates of pressing and what the child says about them may depend upon such variables.

Transfer of function across members of an equivalence class.

A child's presses on response windows behind which stimuli were presented via computer monitor occasionally lit lamps arranged in a column; a present was delivered when all lamps in the column were lit. During the operation of a multiple schedule, the child first learned low rates of pressing in the presence of STAR and high rates in the presence of TREE. Later, in an arbitrary matching task, the child learned to select STAR given wiggly WORM and TREE given BLOCK. When WORM and BLOCK were inserted into the multiple schedule, the low and high rates respectively correlated with STAR and TREE transferred to them. Tests of reflexivity (identity matching) and of symmetry of the arbitrary matching implied that STAR and WORM had become members of one equivalence class, and TREE and BLOCK had become members of another.

Reinforcement schedules: Retroactive and proactive effects of reinforcers inserted into fixed-interval performances.

The responding maintained by a reinforcer depends on the relation of the reinforcer not merely to the response that produces it but also to other preceding responses. Early responses in a sequence that ends in a reinforcing consequence make smaller contributions to later response rates than more recent ones, by virtue of the longer delays that separate them from the reinforcer. This study shows that the relation between a response and a later reinforcer contributes to responding only if no other reinforcers intervene; in other words, each reinforcer blocks responses that precede it from the effects of later reinforcers. Pigeons' pecks were maintained by fixed-interval (FI) schedules of food reinforcement. When FI 60-s (short) and FI 75-s (long) schedules began simultaneously within constant 150-s cycles, long FIs did not affect short-FI performances, but short FIs eliminated the first 60 s of long-FI performances. Removing either short-FI reinforcers or short-FI stimuli showed that short-FI reinforcers and not short-FI stimuli blocked the first 60 s of the long-FI performance from the retroactive effects of the long-FI reinforcer. With FI 15-s and FI 75-s schedules, the short-FI reinforcer was followed by reduced long-FI responding, but a schedule that prevented discrimination based on time since a reinforcer eliminated this proactive effect of the short-FI reinforcer. In other words, the retroactive effects were reinforcer effects whereas the proactive effects were discriminative effects. Quantitative descriptions of variable-interval performances, in which reinforcer effects may operate in the absence of temporal discriminative effects, can be derived from these relations.