Get access

Fear acquisition requires awareness in trace but not delay conditioning


  • This study was supported by grants of the German Research Foundation (DFG) to Almut Weike (We 2762/3-1) and Alfons Hamm (Ha 1593/10-2).

Address reprint requests to: Almut Weike, University of Greifswald, Department of Psychology, Franz-Mehring-Str. 47, 17487 Greifswald, Germany. E-mail:


The present study explored fear acquisition in differential delay versus trace conditioning in regard to the potential role of the acquired contingency awareness. One of two neutral pictures (CS+) either coterminated with (delay group; n=32) or was followed by the aversive unconditioned stimulus (UCS) after CS offset (trace group; n=32), while startle blink and skin conductance responses (SCR) were measured. As expected, the acquisition of conditioned startle potentiation in delay conditioning was independent of contingency awareness. In contrast, fear-potentiated startle in trace conditioning was only observed for those participants who were aware of the CS–UCS contingencies. SCR conditioning was generally only obtained for aware participants. The present results suggest a more implicit learning process in delay fear conditioning, whereas the explicit acquisition of contingency awareness might be a prerequisite for trace fear conditioning.