Figure 3.

Spontaneous recovery of immediately extinguished fear in humans. Mean (±SE) differential SCR (CS+ minus CS−) in each experimental phase is presented. A difference between responses to the CS+ compared to CS− was present during acquisition and immediate extinction but decreased by delayed extinction. The spontaneous recovery test (between vertical solid lines) compared the differential SCR with the first CS+ and CS− presented in re-extinction with the differential SCR to the last CS+ and CS− presented in extinction. Extinction and re-extinction were separated by 24 h (indicated by the vertical dashed line). As can be seen, the differential responding in the last trial of extinction was not significantly different from zero, whereas the differential responding 24 h later was. This increase in differential responding (recovery test) was statistically significant (*P < 0.05; ‡ denotes comparison of the differential conditioned response to zero; ^ denotes comparison between early and late extinction; † denotes recovery test; n.s., not significantly different from zero).