Effects of stimulus content and postacquisition devaluation of the unconditioned stimulus on retention of human electrodermal conditioning and relational learning

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Abstract
The present experiment (W=72) employed a differential conditioning procedure to investigate the effects of fear‐relevance of the conditioned stimulus (CS) and postacquisition exposure to the unconditioned stimulus (US) on the retention of human autonomic conditioning and relational learning. The CSs were pictures of snakes and spiders (fear‐relevant) for half the subjects, and pictures of flowers and mushrooms (fear‐irrelevant) for the other half. A delay conditioning procedure was employed with a GS‐US onset interval of 8 sec. Following the acquisition phase, one group was exposed to 30 presentations of US‐alone, another was exposed to 30 presentations of white noise, and a third group received no stimulation. The dependent variables were the skin conductance response (SCR) and a continuous measure of US expectancy. The results indicated that fear‐relevant CSs elicited larger responses during the adaptation phase and resulted in greater first‐ and second‐interval SCR conditioning than did fear‐irrelevant CSs. However, the test phase data revealed that electrodermal conditioning was not influenced by postacquisition exposure to the US. Expectancy of the US increased in the presence of CS+ during acquisition and expectancy of no‐US increased in the presence of CS‐. Moreover, postacquisition exposure to the US attenuated US expectancy in the test phase. The results are discussed in terms of general‐process theories of conditioning and in terms of the concept of preparedness.