James A. Dinsmoor

Stimulus control: part II.

The second part of my tutorial stresses the systematic importance of two parameters of discrimination training: (a) the magnitude of the physical difference between the positive and the negative stimulus (disparity) and (b) the magnitude of the difference between the positive stimulus, in particular, and the background stimulation (salience). It then examines the role these variables play in such complex phenomena as blocking and overshadowing, progressive discrimination training, and the transfer of control by fading. It concludes by considering concept formation and imitation, which are important forms of application, and recent work on equivalence relations.

Escape-from-Shock Training following Exposure to Inescapable Shock

In this experiment we have studied the effects of exposing rats to non-terminable shock on their subsequent utilization of bar pressing as a means of terminating the shock. Our main findings were: (a) that a 15-min. period of prior exposure significantly delayed the first press in training and significantly reduced the number of presses within a 35-min. session; and (b) that a 15-min. period of exposure between training and extinction altered the shape rather than the initial slope of the extinction curves, producing a significantly more rapid decline in the rate of pressing. These results indicate that competing behavior is acquired when no authorized escape response is available, and that this behavior interferes with the escape response when this is at a low strength but is itself suppressed when the escape response is at a high strength.

Control of avoidance by a response-produced stimulus

Abstract Three pigeons were trained to press a foot pedal to postpone electric shock. The safety signal was a tone of 1000 Hz, which sounded for 5 sec following each press; silence therefore served as a warning signal. After the performance approached asymptote, test sessions were interspersed among the training sessions. Following a warm up, the shock was omitted (extinction), and no tone or a tone of 250, 500, 1000, 2000, or 4000 Hz was presented following each press for the remainder of the session. Gradients of generalization plotted in terms of the number of times the tone was produced on each test peaked at 1000 Hz, indicating that the performance was controlled by the frequency. Since this dimension is orthogonal to absence of tone, the gradient cannot be attributed to differences in the magnitude of change in the warning signal. It was concluded that response-produced stimuli reinforce avoidance behavior.

Wyckoff's observing response: Pigeons learn to observe stimuli for free food but not stimuli for extinction

Abstract Four pigeons received periods of free food delivery alternating with periods of extinction. The experimental chamber was divided in half. Initially the subjects could produce stimuli selectively associated with these schedules by standing on the right side of the chamber and later by standing on the left side. In both phases, subjects produced the free food stimulus most of the time it was available but did not increase above baseline the time spent producing the extinction stimulus. Thus, when alternative stimuli are available, the pigeon prefers the stimulus associated with the greater frequency of reinforcement although the choice results in no biological advantage.

Level of Current and Time between Sessions as Factors in “Adaptation” to Shock

Three groups of 16 rats were exposed to no shock, 200 microamperes, or 400 microamperes, respectively, for 50 min. The next day, half of each group were trained to press a bar to turn off a 200 μa shock and half were trained to turn off a 400 μa shock. The higher the current during the first (exposure) session, the lower and more variable was the rate of pressing during the second (training) session. The higher the current during training, the higher and less variable was the rate of pressing. The persistence of the effects of prior exposure after 24 hr. suggests that some kind of learned behavior is involved.

Differential Production of Positive and Negative Discriminative Stimuli by Normal and Retarded Children.

Abstract Using an observing procedure similar to Wyckoffs (1969) , two normal and two mentally retarded children were studied. The children were initially trained to earn pennies by pressing a rectangular key according to a multiple variable-interval extinction schedule of reinforcement. After discrimination training, the children were allowed to produce the discriminative stimuli by depressing a second or observing key. The retarded children were different from the normal children in that they produced more of the positive discriminative stimulus (S+) than the negative discriminative stimulus (S−). In the case of the retarded children, S+ observing started high and remained high. In the case of the normal children, S+ observing was initially substantial and then rapidly diminished.

Temporal vs. spatial information as a reinforcer of observing

Conditioned reinforcement interpretations of observing behavior predict that certain kinds of temporal information, but not spatial information, will reinforce observing. In a free operant observing experiment, pigeons pecked the left and right keys of a three-key panel to produce intermittent food deliveries. Pecks to the center key (observing responses) produced stimulus displays providing some birds with spatial information (which side key to peck) and other birds with temporal information (which component of a mixed variable-interval/extinction schedule was operating). Four of the six birds that could produce temporal information did so, whereas none of the six birds that could produce spatial information did so. The “information hypothesis” of observing apparently cannot explain this result.

STUDIES IN THE HISTORY OF PSYCHOLOGY: CVI. AN APPRECIATION OF FRED S. KELLER, 1899-1996"

To casual acquaintances, Fred S. Keller may have been known chiefly for his excessive humility, his deadpan wit, his winning way with words, and his propensity for noting and reinforcing the best of the behavior of everyone with whom he came into contact. But to those familiar with the history of the experimental analysis of behavior he was also known as an innovative figure who introduced the use of nonverbal organisms as the laboratory material for the first course in psychology, as coauthor with W. N. Schoenfeld of the classic textbook in the analysis of behavior, as an academic progenitor of something like half of the first generation of behavior analysts, as the founder of scientific psychology in Brazil, and as the principal author of a teaching procedure known as the Personalized System of Instruction.