Psychology ETDs

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The present experiments sought to investigate the effects of intensity of the unconditioned stimulus (UCS) on differential conditioning. The first experiment was an attempt to replicate the Spence, Haggard, and Ross (1958b) study in which one group of subjects (Ss) received, on a random half of the trials, a light conditioned stimulus (CS) paired with a high intensity UCS, while on the other half of the trials, a tone CS was paired with a weak UCS. Another group received the reverse pairing arrangements. Spence, Haggard, and Ross found higher levels of conditioning exhibited by the CSs paired with the higher UCS, and took such results as supportive of Spence's view that UCS intensity affects habit strength as well as drive. The essential aspects of the Spence, Haggard, and Ross study were successfully replicated in the present experiment.

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Department Name


First Committee Member (Chair)

G. Robert Grice

Second Committee Member

Frank A. Logan

Third Committee Member

Henry C. Ellis

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Psychology Commons