Short-term retention of response outcome as a determinant of serial reversal learning

The correlation between short-term retention of the outcome of the preceding response and overall learning proficiency was investigated for serial reversal learning. Pigeons were trained to asymptote on a serial reversal problem and then were presented a percentage reinforcement schedule where only some correct trials were rewarded. Nonrewarded correct trials were treated exactly as incorrect trials. The difference in error probability following the two types of correct trials was then used as a measure of short-term retention. When intertrial intervals (ITI) were short (6 sec), substantial differences occurred. When the ITI's were increased, the difference in accuracy declined regularly to no difference at an ITI of 60 sec. This demonstration of a short-term retention gradient, coupled with the finding that overall reversal learning was much better with the shorter ITI's, suggests that a primary mechanism of improvement in serial reversal learning is the acquisition of a conditional discrimination based on the outcome of the preceding response.     

Effects of postresponse visual stimuli on visual discrimination learning in the rhesus monkey

To learn more about the mechanism (or mechanisms) involved with postresponse stimulus processing during discrimination learning, a series of studies was conducted with monkeys to determine why the combined relevant and irrelevant stimuli impair learning more than irrelevant stimuli appearing alone. It was found that: (a) the greater size and complexity of the combination of stimuli were not responsible for the greater deficit, while the presence of the relevant stimuli (S^D and S^Δ) within the stimulus combination apparently was; (b) the more similar the postresponse irrelevant stimuli were to the relevant stimuli the greater the deficit that resulted; and (c) monkeys that had earlier learned to discriminate the relevant and irrelevant features of a combination showed no learning impairment when this same stimulus combination was later presented after the response during a new learning problem. These results were interpreted as evidence that: (1) processes associated with learning a discrimination problem do not end with the execution of a choice response; (2) postresponse stimuli produce greater impairment in discrimination learning when they are distorted versions of the relevant stimuli; and (3) the impairment resulting from postresponse irrelevant stimuli occurs primarily when this misinformation is processed and misperceived as being relevant to learning the discrimination problem.     

Configural conditioning in the CER: Loss of element strength after repeated reinforced compound CS trials

Different groups of rats received different numbers of compound CS (light/noise) conditioning trials in the CER procedure. The amount of suppression evident to the single elements of the compound decreased as a function of the number of previous compound trials. This loss of CR strength was interpreted as a configuring effect. Further experimental comparisons indicated that the configuring effect could not be readily explained in terms of a generalization decrement or a stimulus novelty hypothesis.     

Positive contrast following gradual and abrupt increases in reward magnitude using delay of reinforcement

In Experiment 1, rats were given a 1-pellet reward for 48 preshift trials. During a subsequent 20-trial postshift phase, one group was shifted to a 12-pellet reward on Trial 1, a second was shifted on Trial 11, and a third was given 1 more pellet each trial and then 12 pellets for the last 10 trials. The speeds of all three groups increased to a level above that of a control group given a 12-pellet food reward throughout training (positive contrast). In experiment 2, rats were shifted from 1 to 12 pellets either gradually or abruptly following either abbreviated training (9 trials) or extended training (20 trials). One group of control subjects received 12 pellets throughout training. The results revealed a positive contrast effect for gradually shifted subjects following extended training but not following abbreviated training. The abrupt shift procedure produced positive contrast following abbreviated training but only a marginal effect following extended training. These results indicate that, contingent upon the amount of preshift training, either gradual or abrupt reward increases may produce positive contrast.     

Effect of sample presentation time on long-delay matching in the pigeon

The effect of sample stimulus presentation time on long-delay matching in highly practiced pigeons was investigated. The birds were found capable of above chance matching performance at a delay of 60 sec provided the sample stimulus was presented for 4 sec or longer. Matching accuracy increased as a negatively accelerated function of sample stimulus presentation time and decreased as a negatively accelerated function of time since the termination of the sample. The rate of forgetting was found to be independent of sample stimulus presentation time. The data were inconsistent with a temporal discrimination interpretation of the effect of presentation time on delayed matching. The data were interpreted as supporting a simple trace strength and decay model of pigeon delayed matching.     

Effects of schedule and magnitude of reinforcement under conditions of thirst motivation

In contrast to a recent finding (Macdonald, G. E., & De Toledo, L. Learning and Motivation, 1974, 5, 288–298.) the results of three experiments investigating various partial reinforcement (PRF) manipulations under conditions of thirst motivation demonstrated strong similarity to analogous manipulations involving food reward. Specifically, for animals receiving water reinforcement, PRF was shown to generate greater resistance to extinction than continuous reinforcement (Expt 1 & 3), the schedule of reinforcement was shown to interact with level of acquisition (Expt 1 and 2), and the magnitude of the partial reinforcement extinction effect was shown to be a function of reward magnitude (Expt 3). These results provide strong evidence that mechanisms which operate in partial reinforcement situations are highly similar, regardless of the type of appetitive reinforcement.     

Changing roles for the school mental health professional

Draws on the experience of an innovative school mental health project, emphasizing early detection and prevention of school adjustment problems, to describe emergent, needed roles for school psychologists. The later include: systematic screening of primary graders and parent interviewing to further early detection; consultation with teachers and other school personnel; and recruitment, training, and supervision of nonprofessional help-agents. Such roles bring early effective services to many children, in ways that optimize their educational and personal development.     

Physical distance and attraction: An intensification effect

This study was designed to test the effects of both interaction distance and the quality of the interaction upon attraction. It was found that close interaction distances amplified the quality of the interaction so that for a positive interaction there was more liking for a close rather than a far partner, while for a negative interaction a close partner was liked less. The implications of this finding for research concerning crowding is discussed, as are possible explanatory mechanisms.     

Delayed effects of practiced versus unpracticed responses after observation of movie violence

University men participating in an ostensible study of “impression formation” first received either an insulting or neutral evaluation of themselves from their supposed partner and then watched either a prize fight or an exciting but nonaggressive scene. After this, they either had an opportunity to evaluate their partner right away or they had to wait an hour before evaluating him. On scoring the subjects' written statements about the partner (to be seen by him and the experimenter), it was found that (1) for those given the immediate opportunity to be aggressive, the violent movie increased the strength of the angered subjects' initial attack on their partner over that displayed by the similarly insulted men shown the nonaggressive film; (2) if the angry subjects had to wait an hour before evaluating their partner, there was no difference between the aggressive and nonaggressive movie groups; (3) the aggression-heightening effect of the violent scene did carry over the intervening hour, however, if the insulted men had been given the earlier opportunity to evaluate their partner. It is suggested that the performance of an aggressive response soon after seeing an aggressive film increases the persistence of the aggressive reactions over time.     

Group caution at the race track

McCauley, Stitt, Woods and Lipton's finding that groups were more conservative than individuals when betting at a race track has been criticized on statistical and methodological grounds. The present study which does not suffer the shortcomings for which McCauley et al. were legitimately criticized does, nonetheless, sustain their general results and conclusions. Groups were significantly more cautious than individuals when wagering $2.00 on a horse race.