The evoked cardiac response (ECR) of heart rate deceleration, the skin resistance response (SRR), respiratory pause, and the peripheral pulse amplitude response (PPAR) of vascular constriction were examined in 30 subjects using a dishabituation paradigm. Ten trials of one stimulus magnitude were followed by an interpolated change trial of a different magnitude, and five trials of the orginal magnitude. Results indicated that ECR was consistent in amplitude, failing to reflect any aspect of stimulus manipulation, PPAR behaved as an absolute indicator of stimulus magnitude and respiratory pause reflected stimulus novelty. SRR exhibited stimulus novelty and magnitude effects, recovery to the change stimulus and dishabituation with the following stimuli. These results are incompatible with unitary OR theory and provide support for an alternative multi-register theory of preliminary processes in OR elicitation. © 1981.