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Title: Processes and mechanisms of stimulus over-selectivity
Author: Reynolds, Gemma
Awarding Body: Swansea University
Current Institution: Swansea University
Date of Award: 2011
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Stimulus over-selectivity refers to the phenomenon whereby behaviour becomes controlled by one element of the environment at the expense of other equally salient aspects of the environment. It is a common problem for individuals with autism, learning disabilities, acquired neurological brain damage, the elderly and typically developing individuals under-going a cognitively demanding task. The current thesis presents 15 experiments that investigate the mechanisms of over-selectivity and explore potential remediation techniques. All experiments employed a simultaneous discrimination procedure using non-clinical participants under-going a cognitively taxing task. Experiments 1-3 demonstrated the robustness of over-selectivity across a range of test conditions. Experiments 5 and 6 extended this by exploring the potential role of conditioning effects and found no evidence of inhibition accruing to the under-selected stimulus. Experiment 4 showed that following extinction of the previously over-selected stimulus, the under-selected stimulus could emerge to control responding despite receiving no further direct training, thus supporting the use of extinction techniques to reduce over-selectivity. Experiment 7 indicated that partial reinforcement (PR) did not reduce over-selectivity and actually increased over-selectivity when participants underwent less training (Experiment 8). Experiments 9 and 10 showed that changing schedule of reinforcement from continuous reinforcement (CRF) to PR or from PR to CRF also failed to reduce overselectivity. Experiment 11 found a reduction in over-selectivity following a downward shift in reinforcer value, whilst Experiment 12 ensured that neither generalisation decrement nor PR influenced this effect. Experiments 13 and 14 suggested that the decrease in over-selectivity was due to a change in the unconditioned stimulus as opposed to changing the nature of the stimuli. Finally, Experiment 15 showed no reduction in over-selectivity when the reinforcer was qualitatively manipulated. These results are discussed in terms of theoretical perspectives of over-selectivity, and implications for the remediation of the effect.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Autism spectrum disorders ; Learning disabilities ; Behaviorism (Psychology)