Interference between cues of the same outcome depends on the causal interpretation of the events.

In an interference-between-cues design, the expression of a learned Cue A --> Outcome 1 association has been shown to be impaired if another cue, B, is separately paired with the same outcome in a second learning phase. In the present study, we assessed whether this interference effect is mediated by participants' previous causal knowledge. This was achieved by having participants learn in a diagnostic situation in Experiment 1a, and then by manipulating the causal order of the learning task in Experiments 1b and 2. If participants use their previous causal knowledge during the learning process, interference should only be observed in the diagnostic situation because only there we have a common cause (Outcome 1) of two disjoint effects, namely cues A and B. Consistent with this prediction, interference between cues was only found in Experiment 1a and in the diagnostic conditions of Experiments 1b and 2.