Thesis (M.S)--University of Wisconsin-Madison, 1964. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 47-48).

The present study is an attempt to determine which of several different types of reinforcers is most effective in discrimination learning using institutionalized mentally retarded boys of different intellectual levels as subjects. If one type of reinforcement works more effectively in conditioning one level of institutionalized mentally retarded subject, then that type of reinforcement could be used to greater advantage in controlling behavior than some other, less effective kind of reinforcer.

Using both incomplete and complete triads methods , dimensional preference (form or color) was assessed in 121 children (mean age 79.1 months) either before or after performance in a discrimination learning task to determine the effect which prior preference tests have upon the relations between dimensional preference and discrimination learning. The results indicated little support for the perceptual-differentiation hypothesis and some support for both the attentional hypothesis and the developmental-mediational hypothesis . The complete triads method was recommended as an improvement over the incomplete triads and opposed cues methods of preference assessment because the former allows E to determine Ss ability to function in his nonpreferred dimension.

No description available.

No description available.

Thesis (Ph. D.)--University of Wisconsin -- Madison, 1954. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 45-46).

Behavioral flexibility, the ability to change behavior in accordance with the changing environment, was studied in pigeons using a series of reversal learning paradigms. All experiments involved a series of 5-trial sequences and I was interested in whether pigeons are sensitive to the reversal by switching to the other alternative after a single error. In Experiments 1 and 2, the overall probability of the two stimuli was equated over sequences, but the probability correct of the two stimuli changed across trials. In both experiments, subjects showed no sensitivity to the differences in sequence type. Instead they used the overall average of the probability of reinforcement on each trial as the basis of choice. In the final two experiments, the likelihood that a reversal would occur on a given trial was equated such that there was an equal overall probability that the two stimuli would be correct on a given trial, but the overall probability of each stimulus being correct across sequences favored the second correct stimulus (S2). In Experiment 3, the overall probability of S2 correct was 80%, and results showed that subjects consistently chose S2 regardless of sequence type or trial number. In Experiment 4, the overall likelihood of S2 correct was 65%, and results showed that subjects began all sequences at chance, and as the sequence progressed, began choosing S2 more often. In all experiments, subjects showed remarkably similar behavior regardless of where (or whether) the reversal occurred in a given sequence. Therefore, subjects appeared to be insensitive to the consequences of responses within a sequence (local information) and instead, seemed to be averaging over the sequences based on the overall probability of reinforcement for S1 or S2 being correct on each trial (aggregate information), thus not maximizing overall reinforcement. Together, the results of this series of experiments suggest that pigeons have a basic disposition for using the overall probability instead of using local feedback cues provided by the outcome of individual trials. The fact that pigeons do not use the more optimal information afforded by recent reinforcement contingencies to maximize reinforcement has implications for their use of flexible response strategies under reversal learning conditions.

"Stable multi-day recordings from chronically implanted microelectrodes within the dorsolateral prefrontal cortex of two monkeys performing three Go/NoGo visual discrimination tasks (one requiring well-learned responses, two requiring learning) demonstrated that the majority of prefrontal neurons were 'functionally stable'. Action potentials of 94 neurons were stable over 2-9 days; 66/94 (70%) of these cells responded each day, 22/94 (23%) never responded significantly, and 6/94 (6%) responded one day but not the next. Of 66 responsive neurons, 55 were selective for either Go or NoGo trials, individual stimuli, or eye movements." (Greenberg and Wilson, 2004) Selectivity was maintained, for 46/55 neurons across all recording days. Response strength (baseline vs. post-stimulation firing rates) and event-related response timing also displayed stability. Stability generalized across neuronal response type suggesting that functional stability is a general property. Long-term recordings from other studies supported similar conclusions suggesting that neurons throughout the brain are functionally stable. Single-day recordings from different neurons within the same cortical regions demonstrated neuronal response flexibility while monkeys learned associations among visual cues, and Go/NoGo behavioral responses. Of 116 neurons, 57 (49%) displayed significant change points in firing rates during novel learning (n=18), reversal learning (n=12), or both tasks (n=27). Six of 57(10.5%) neurons had firing rates changes prior to learning and might have been causally related to the monkeys' behavioral changes. However, only 18/152 (12%) of the total number of firing rate changes occurred prior to the monkeys' learning meaning that most appeared to be the consequences of learning rather than the causes.

No description available.

The problem was to determine the levels of intellectual capacity necessary at various ages for acquiring rapid and efficient nonspatial discrimination learning sets on problems of increasing complexity.