Classical conditioning of human systolic pressure: replication and extension using three stimulus durations.

Recent efforts have demonstrated classical conditioning of human systolic pressure (De Leon, 1972). The present research attempted a replication with longer sessions and to maximize the CS+, CS- differentiation by varying CS+ durations. Student volunteers (N = 64) underwent four, 50 minute sessions, three conditioning and one extinction, distributed over two weeks. Shock (UCS) occurred intermittently in light-on (CS+) and never in light-off (CS-). Results closely replicated the earlier work, revealing a characteristic UCR, a significant CS+, CS- differential and, conditioned elevations failed to adapt within and across sessions. The pressure differential was inversely related to CS+ duration. Clarification of conditioning influences requires follow-up research on these clients outside of the laboratory. Nevertheless, these studies provide firm experimental evidence for implicating stimulus variables in the origins of certain hypertensive states.