In the context of fear conditioning, different psychophysiological measures have been related to different learning processes. Specifically, skin conductance responses (SCRs) have been related to cognitive expectancy learning, while fear potentiated startle (FPS) has been proposed to reflect affective learning that operates according to simple associative learning principles. On the basis of this two level account of fear conditioning we predicted that FPS should be less affected by verbal instructions and more affected by direct experience than SCRs. We tested this hypothesis by informing participants that contingencies would be reversed after a differential conditioning phase. Our results indicate that contingency reversal instructions led to an immediate and complete reversal of FPS regardless of the previous conditioning history. This change was accompanied by similar changes on US expectancy ratings and SCRs. These results conform with an expectancy model of fear conditioning but argue against a two level account of fear conditioning.