Competition and facilitation in compound conditioning

Despite the generality and theoretical relevance of cue competition phenomena such as blocking and overshadowing, recent findings suggest that these observations may be due to some degree of publication bias, and that we lack insight into the boundary conditions of these phenomena. The present commentary does not question the existence of cue competition phenomena. Rather, I review findings showing that three variables, namely 1) relative stimulus duration, 2) contingency, and 3) contiguity parametrically determine not only whether cue competition is observed, but also whether no cue interaction, or cue facilitation occur. I discuss theoretical interpretations and implications of these findings, which may provide illuminating insights into the generality and functional significance of the commonly cited ‘principles of learning’.