What are the cognitive processes underlying people's decisions from memory? Previous research suggests that these processes can be best described by strategies that are based on abstract knowledge about the decision task (e.g., cue–criterion relations). However, recent results show that different cue presentation formats trigger the use of different decision strategies and that exemplar-based strategies can account for memory-based decisions as well. In three experiments, this effect was replicated, and mediation analyses identified the quality of the underlying knowledge representation as the critical variable that determines decision behavior. This supports the view that exemplar-based reasoning is used as a backup system if cue abstraction is hindered. Copyright © 2012 John Wiley & Sons, Ltd.