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Biomedical subjects

D R Thomas

Publications and source records attributed to D R Thomas.

At least 163 records · Page 9Linked to original sources
PubMed1971

On the form of stimulus generalization curves for visual intensity.

Twelve pigeons were given successive discrimination training involving variable-interval reinforcement for key pecking in the presence of one intensity of monochromatic light randomly alternated with extinction for pecking during another intensity. All of the pigeons were then tested in extinction for generalization along the intensity dimension, and all showed a displacement of maximal responding from the positive stimulus in the direction opposite the negative stimulus. For six of the pigeons, for which the test included only three values beyond the positive stimulus, four showed peaked gradients but two did not, showing monotonic gradients with maximal responding to the most extreme test value. For another six pigeons tested over a wider range, all showed peaked gradients. Thus, when a sufficiently wide range of test values is employed, generalization gradients for visual intensity have the same peaked form as do gradients for qualitative visual dimensions such as wavelength or line angle.

Animals↗
PubMed1969

Stimulus generalization as a function of the delay between training and testing procedures: a reevaluation.

Three groups of 12 pigeons each were trained to discriminate between lights of 550 mmu (S(D)), correlated with 1-min variable-interval reinforcement and 570 mmu (S(Delta)), correlated with extinction. Group A was tested for wavelength generalization in extinction 1 min after meeting the discrimination criterion; Group B was tested 24 hr later; Group C was tested 24 hr later after a 3-min (reinforced) warm-up with the S(D). The post-discrimination gradient of Group B was significantly flatter and showed significantly greater area shift than that of Groups A and C. The gradient of Group C was similar to that of Group A, indicating that the warm-up eliminated the effect of the delay period.

Journal Article↗
PubMed1969

Reinforcement duration and the peak shift in post-discrimination gradients.

Pigeons were trained to key-peck for food, first with single-stimulus training and then with successive discrimination (multiple schedule) training. In the multiple schedule, two different wavelengths were each correlated with equally frequent variable-interval reinforcement but different durations (6 sec vs. 2 sec) of access to grain. For some birds, the different durations of feeding cycle were cued by different intensities of the food hopper light. For some of these "cued" birds, single-stimulus training had been carried out with 6-sec feedings and when multiple-schedule training was introduced, the novel stimulus was correlated with 2-sec feedings. For the others, 2-sec feedings were originally used, and the novel stimulus was then present during the 6-sec reinforcement duration. The cueing procedure enhanced discrimination performance, and was necessary for the consistent production of a peak shift. In addition, the condition in which original training had been carried out with 6-sec feedings, and thus reinforcement duration was reduced in the presence of the novel stimulus, led to the best performance.

Journal Article↗
PubMed1968

Rules, praise, and ignoring: elements of elementary classroom control.

An attempt was made to vary systematically the behavior of two elementary school teachers to determine the effects on classroom behavior of Rules, Ignoring Inappropriate Behaviors, and showing Approval for Appropriate Behavior. Behaviors of two children in one class and one child in the other class were recorded by observers, as were samples of the teachers' behavior. Following baseline recordings, Rules, Ignoring, and Approval conditions were introduced one at a time. In one class a reversal of conditions was carried out. The main conclusions were that: (a) Rules alone exerted little effect on classroom behavior, (b) Ignoring Inappropriate Behavior and showing Approval for Appropriate Behavior (in combination) were very effective in achieving better classroom behavior, and (c) showing Approval for Appropriate Behaviors is probably the key to effective classroom management.

Journal Article↗
PubMed1968

Production and elimination of disruptive classroom behavior by systematically varying teacher's behavior.

The effects of teacher behaviors on the classroom behaviors of children were investigated by systematically varying approving (praise, smiles, contacts, etc.) and disapproving (verbal reprimands, physical restraint, etc.) classes of teacher behavior. Measures were taken on both teacher and child behaviors. Each day a sample of 10 children was observed. The subject pool was a class of 28 well-behaved children in a middle-primary public school class. The results demonstrated that approving teacher responses served a positive reinforcing function in maintaining appropriate classroom behaviors. Disruptive behaviors increased each time approving teacher behavior was withdrawn. When the teacher's disapproving behaviors were tripled, increases appeared most markedly in the gross motor and noise-making categories of disruptive behavior. The findings emphasize again the important role of the teacher in producing, maintaining, and eliminating disruptive as well as pro-social classroom behavior.

Journal Article↗
PubMed1968

Further evidence of a sensory-tonic interaction in pigeons.

The five pigeons in Group 1 were given successive intradimensional discrimination training in which responses to a line of 49 degrees were reinforced on a variable-interval schedule and responses to a line of 33 degrees were not reinforced. Subsequent generalization testing with other line orientations revealed a peak shift from the positive stimulus in the direction away from the negative stimulus in all subjects. The four pigeons in Group 2 received successive discrimination training with the 49 degrees value on the key during both stimuli. During the negative stimulus, however, the floor was tilted 16 degrees counterclockwise. When tested (with the floor flat) these subjects showed peak shifts similar to those observed with Group 1. A third group of three pigeons, given successive interdimensional discrimination training with the 49 degrees line as the positive stimulus and the absence of the line as the negative, showed no peak shift in a subsequent generalization test. It was concluded that tilting the floor on which the pigeon stood systematically distorted the bird's visual perception of the orientation of the line in a manner consistent with the results of other studies in this laboratory.

Animals↗