When an aversive stimulus (S2) follows a weak neutral stimulus (S1), the responses to S2 are modified. Compared with an S2-alone control, facilitation occurs in the long-ISI (e. g., 8 s) condition, while inhibition occurs in the short-ISI (e. g., . 5s). The S1 employed in this kind of study can have the three properties of time, warning, and physical stimulation as a signal. In this study, the relations between response modifications and S1 properties were investigated, using the response measures of the eyeblink reflex and subjective aversiveness ratings. In addition to demonstrating the importance of the ISI variable, the results indicated that in the eyeblink reflex, the S1 with only a physical stimulation property was necessary for facilitation, while the S1 with at least time and physical stimulation properties was necessary for inhibition, and in the aversiveness ratings, the S1 with at least a physical stimulation property was necessary for inhibition, while no facilitation was found whatever property S1 had.
View full abstract