Walter Vom Saal

Blocking the development of stimulus control

Abstract Two experiments evaluated the possibility that prior discrimination training on red versus green would block the development of stimulus control by tone versus noise when both stimulus dimensions simultaneously predicted reinforcement. The key pecking response of pigeons was used in a discriminated trial procedure. In Phase 1 of Exp. I, Group D learned a go no -go discrimination based on red versus green, Group N was not run, Group R received reinforced trials only, and Group P received partial reinforcement. In Phase 2, all groups learned a go no -go discrimination based on tone-plus-red versus noise-plus-green. When tested after Phase 2, Group D showed less auditory control than any other group. The difference between Groups D and P was confirmed in Exp. II. These results show that blocking occurred, while ruling out a number of other factors that may have caused apparent blocking in previous experiments.

Choice between stimuli previously presented separately

Abstract Three experiments examined the choice behavior of pigeons in a chamber with two adjacent keys that could each be lit with either a red or a green dot. In each experiment subjects first received several sessions of separate-stimulus training with only one color present on each trial, then a choice test with both colors present on each trial. Trials lasted a fixed period of time regardless of the number of pecks that occurred, with earned reinforcements presented at the end of the trial; no reinforcement was available during choice tests. When separate-stimulus training was arranged so that more reinforcements occurred per unit time with S 1 present than with S 2 present, either because responding was reinforced on a higher proportion of S 1 trials or because S 1 trials were shorter, S 1 was pecked more often on the subsequent choice test. When reinforcements per unit time with the stimulus present were held constant, a number of other variables had little or no effect on subsequent choice, including total number of trials presented, proportion of trials followed by reinforcement, trial length, and total number of reinforcements per session with each stimulus.

Preference for predicted over unpredicted shock

Rats received unavoidable, inescapable shock at each end of a shuttle box. A predictive signal preceded the shock when the rat was at one end of the shuttle box, while a random signal was presented when the rat was at the other end. Subjects spent significantly more than 50% of their time at the end with the predictive signal. Examination of crossover data suggested that the occurrence of crossover responses from one end to the other was influenced by the consequences of those responses, and raised the possibility that preference for predicted shock in this and previous studies was due to differential consequences that normally exist for crossover responses in each direction.

Preference between fixed-interval and variable-interval schedules of reinforcement: Separate roles of temporal scaling and predictability

Pigeons’ preference between fixed-interval and variable-interval schedules was examined using a concurrent-chains procedure. Responses to two concurrently available keys in the initial links of the concurrent chains occasionally produced terminal links where further responses were reinforced under either a fixed- or variable-interval schedule. In previous studies, preferences for the variable schedule with such a procedure have been interpreted as reflecting atemporal scaling process that heavily weights the shorter intervals in the variable schedule. The present experiment examined whetherpredictability, i.e., the presence of external stimuli correlated with the reinforcement interval, might also influence preference in such situations. When the two intervals in a variable schedule were made predictable by being associated with different key colors, preference for that schedule increased. This increase was reliable but small in magnitude and transient when initial-link responses only occasionally produced terminal links; it was large in magnitude when only one response in the initial link was required to produce the appropriate terminal-link schedule. The results suggest that preference between fixed and variable schedules may be influenced both by temporal scaling and to a lesser extent by predictability of the reinforcement intervals.

Respiratory Relief Therapy A New Treatment Procedure for the Reduction of Anxiety

A controlled experiment examined the effectiveness of Respiratory Relief Therapy in reducing public speaking anxiety in college students. The therapy employed two procedures: (a) a systematic desensitization paradigm in which the competing response paired with scene presentations was the relief experienced when the student breathed again after exhaling and holding his or her breath out for as long as possible; and (b) homework assignments to practice breathing deeply and regularly. In this study 60 speech-anxious college students were divided into three groups: a Respiratory Relief Therapy group; a Gradual Repeated Exposure group in which students imagined hierarchy items without initiating a competing response in order to control for placebo and expectancy effects; and a Waiting-List control group in which students were evaluated, waited four weeks, were evaluated again, and then offered treatment. Pre and postmeasures, including self-ratings of anxiety, physiological measures (GSR and pulse rate), and blind observer ratings of videotaped public speaking episodes, showed significantly greater reductions in public speaking anxiety in the Respiratory Relief Therapy group than in the other two groups on most measures, supporting the effectiveness of this procedure in reducing specific anxieties in a controlled experimental setting.

Getting started with microcomputers in undergraduate education: Hints and guidelines

Microcomputers can serve many functions in undergraduate education, including control of laboratory experiments, presentation of classroom demonstrations, generation of handouts, and monitoring student performance. Panel members of a symposium presented several general guidelines for the use of microcomputers, and specific guidelines for selecting and purchasing equipment and for daily operation of a microcomputer facility.

Choice based on separately established response tendencies: The effect of recency of reinforcement☆

Abstract The responding of pigeons was studied in a chamber with two adjacent keys that could each be lit with either a red or a green dot. Fixed-length trials were used, with pecking on positive trials reinforced by presenting food at the end of the trial. In each session the first 40 trials were one-key trials with one key lit on each trial, either red or green, and the next four trials were choice trials with both keys lit, one red and the other green. When blocks of sessions were presented in which all one-key trials were positive trials of a single color, choice responding gradually shifted to the color presented most recently during one-key trials. When all one-key trials were nonreinforced trials of a single color, responding on choice trials shifted toward the other color. When positive one-key trials of one color were intermingled with negative one-key trials of the other color, choice responding shifted exclusively to the reinforced color. These shifts in choice responding occurred even when responding on choice trials was never reinforced, and were viewed as based on separate response tendencies for pecking red and pecking green built up during one-key trials.

Computer production of punched paper tapes for controlling experiments

Controlling experiments with paper-tape readers often requires the production of complex paper tapes. A program was written to allow automatic production and checking of complex punched paper tapes using a small computer. The user first defines the punches or punch sets to be used. He then specifies, for each successive block of tape to be punched, the number of punch sets of each type to occur and whether those punch sets should be copied in order or automatically randomized. The specified tape is then produced using a two-pass procedure, after which the tape may be automatically checked for punching errors if desired. The program has facilities for retention or modification of user commands from previous runs, simplifying the production of a large number of tapes with similar characteristics.

Using microcomputers to control student-designed research in a research methods course

Microcomputers may be used to simulate traditional equipment in the psychology laboratory, such as tachistoscopes, memory drums, and reaction timers. With the diminishing price of microcomputers, such simulation is especially attractive, since it is considerably less expensive than the original special-purpose equipment, and also allows greater versatility. The undergraduate laboratory described here requires only inexpensive microcomputers, simple experimental control programs, and little or no additional peripheral equipment.