Although exposure therapy is an effective treatment for anxiety disorders, fear sometimes returns following successful therapy. The Rescorla-Wagner model predicts that presenting two fear-provoking stimuli simultaneously (compound extinction) will maximize learning during exposure and reduce the likelihood of relapse. Participants were either presented with single extinction trials only or single extinction trials followed by compound extinction trials. Additionally, participants within each extinction group were randomized to caffeine or placebo ingestion prior to extinction to investigate the mechanism by which compound extinction may maximize learning (enhanced associative change or enhanced responding). Participants presented with compound trials demonstrated significantly less fear responding at spontaneous recovery compared with participants who received single extinction trials only. Ingestion of caffeine also provided some protection from spontaneous recovery (as measured by valence ratings). At the reinstatement test, only compound extinction trials predicted less fear responding; caffeine ingestion prior to extinction did not attenuate reinstatement effects.