Contingency and stimulus change in chained schedules of reinforcement

Higher rates of pecking were maintained by pigeons in the middle component of three-component chained fixed-interval schedules than in that component of corresponding multiple schedules (two extinction components followed by a fixed-interval component). This rate difference did not occur in equivalent tandem and mixed schedules, in which a single stimulus was correlated with the three components. The higher rates in components of chained schedules demonstrate a reinforcing effect of the stimulus correlated with the next component; the acquired functions of this stimulus make the vocabulary of conditioned reinforcement appropriate. Problems in defining conditioned reinforcement arise not from difficulties in demonstrating reinforcing effects but from disagreements about which experimental operations allow such reinforcing effects to be called conditioned.     

The effects of environmental change on chicks' responses to a familiar stimulus

The purpose of the present experiments was to explore chicks' proximity seeking behaviour in relation to imprinting objects in unfamiliar settings. Experiment I showed that chicks, which were individually imprinted on a stationary imprinting object, displayed reduced proximity seeking behaviour when tested in a pen smaller than the rearing pen. This finding confirmed earlier work on the effects of changed pen size. Experiment II used continuous and intermittent noise rearing and testing conditions, in all possible combinations, and a stationary imprinting object. Increased proximity seeking was found in conditions where the auditory environment was changed from rearing to testing, a result apparently opposite to that obtained in earlier work. It is suggested that the effect of environmental change on proximity seeking may vary with the modality in which change occurs and the salience of the imprinting object.     

An aggression machine II. Interindividual differences in the aggressive defence responses aroused by varying stimulus conditions

PitkÄnen, L. An aggression machine. II. Interindividual differences in the aggressive defence responses aroused by varying stimulus conditions. Scand. J. Psychol., 1973, 14, 65–74.-The subjects, six aggressive and nonaggressive groups of ten 9-year old boys, selected by rating method, were tested with an "aggression machine" (PAM) constructed by the writer. The varying stimulus conditions included two situations of impulsive aggression and six variations of specified attackers. The results showed that (1) the larger part of the variance of the intensity of aggression in the PAM was accounted for by the situational variations than by interindividual differences in coping with thwarting situations as measured by a rating method. (2) The overtly aggressive boys showed strong discrimination between the situations, while the overtly nonaggressive boys were quite insensitive to situational variations. (3) The intensity of aggressive defence towards a boy of the same age correlated most highly with rated aggressiveness. (4) The latency, duration, and number of aggressive responses did not vary as easily as the intensity according to situations.     

Empirical validation of a procedure to correct position and stimulus biases in matching-to-sample

The development of position and stimulus biases often occurs during initial training on matching-to-sample tasks. Furthermore, without intervention, these biases can be maintained via intermittent reinforcement provided by matching-to-sample contingencies. The present study evaluated the effectiveness of a correction procedure designed to eliminate both position and stimulus biases. Following key-peck training, a group of 6 pigeons had extended exposure to matching-to-sample contingencies without a correction procedure, a group of 4 pigeons was briefly exposed to a simultaneous matching-to-sample procedure to assess biases prior to exposure to the correction procedure, and a group of 5 pigeons was exposed directly to the correction procedure. The correction procedure arranged that every time an incorrect match was made, the trial configuration was repeated on the subsequent trial until a correct match was made. Extended exposure to matching-to-sample contingencies without a correction procedure was associated with reduced biases eventually for most subjects, but rapid development of near-perfect accuracy and bias-free performance was observed upon the implementation of the correction procedure regardless of the type of bias. Bias-free performance was maintained following subsequent exposure to a zero-delay MTS procedure.     

Focus of attention, chronic expectancy, and responses to a feared stimulus.

An attentional model of fear-based behavior is proposed and a study that tested the model is reported. It was predicted that among subjects with moderate fear of snakes, heightened self-attention during an approach attempt would cause increased awareness of existing anxiety, followed by one of two courses of events: Subjects who believed that they could do the behavior in spite of their fear were expected to redirect their attention to the behavior--goal comparison and exhibit no behavioral deficit. Subjects who doubted their ability to do the behavior were expected to divert their attention from the behavior--goal comparison and to withdraw behaviorally from the approach attempt. The results of the study support this reasoning. Discussion centers on relationships between the proposed model and previous theory.     

Humor response as related to violation of expectancies and to stimulus intensity in a weight-judgment task.

In a study of humor disguised as a psychophysical task, 60 subjects judged an initial series of 10 weights which was either light or heavy and then a shift weight which was either light, medium, or heavy. Degree of humorous response varied with the discrepancy of the shift weight and its absolute magnitude.     

Independence of stimulus discriminability from absolute rate of reinforcement in a signal-detection procedure.

Three experiments are reported in which two pigeons were trained to detect differences in stimulus duration under varying levels of absolute rate of reinforcement. Two red stimuli, differing in duration, were arranged probabilistically on the center key of a three-key chamber. On completion of the center-key duration, the center keylight was extinguished and the two side keys were illuminated white. Correct responses were left-key pecks following the shorter duration and right-key pecks following the longer duration. In Experiment 1, relative rate of reinforcement for correct responses was held constant and absolute rate of reinforcement was varied in seven conditions from continuous reinforcement to a variable-interval 90-second schedule. In Experiment 2, relative rate of reinforcement was manipulated across three different absolute rates of reinforcement (continuous reinforcement, variable-interval 15-second, and variable-interval 45-second). Stimulus discriminability was unaffected by changes in absolute or relative rates of reinforcement. Experiment 3 showed that discriminability was also unaffected by arranging the same consequences (three-second blackout) for unreinforced correct responses and errors.     

Understanding the dynamics of correct and error responses in free recall: Evidence from externalized free recall

The dynamics of correct and error responses in a variant of delayed free recall were examined in the present study. In the externalized free recall paradigm, participants were presented with lists of words and were instructed to subsequently recall not only the words that they could remember from the most recently presented list, but also any other words that came to mind during the recall period. Externalized free recall is useful for elucidating both sampling and postretrieval editing processes, thereby yielding more accurate estimates of the total number of error responses, which are typically sampled and subsequently edited during free recall. The results indicated that the participants generally sampled correct items early in the recall period and then transitioned to sampling more erroneous responses. Furthermore, the participants generally terminated their search after sampling too many errors. An examination of editing processes suggested that the participants were quite good at identifying errors, but this varied systematically on the basis of a number of factors. The results from the present study are framed in terms of generate-edit models of free recall.