(a) Experimental design and timeline. (b) Mean differential SCRs (CS+ minus CS−) during acquisition (late phase), extinction (last trial) and re-extinction (first trial) for each experimental group (10 min reminder, 6 hr reminder, and no-reminder). The three groups showed equivalent fear acquisition and extinction. Spontaneous recovery (first trial of re-extinction versus the last trial of extinction) was found in the group that had not been reminded or that was reminded 6 hours prior to extinction. In contrast, there was no spontaneous recovery in the group reminded 10 min before extinction. *Significant difference between acquisition and extinction, or extinction and re-extinction within group at p < 0.05; Error bars represent standard errors