International Journal of Comparative Psychology

Five experiments investigated the roles of contingency and temporal contiguity in causal reasoning, and the trade-off between them. Participants observed an ongoing, continuous stream of events, which was not segmented into discrete learning trials. Four potential candidate causes competed for explanatory strength with respect to a single dichotomous effect. The effect was contingent on two of these causes, with one of these (A) having a higher probability of producing the effect compared to the other (B), while B was more contiguous to the effect than A. When asked to identify the strongest cause of the effect, participants consistently and reliably selected A, as long as it was not separated from the effect by more than 2.5 s. The extent of preference diminished, however, as the contiguity gradient between A and B increased. Beyond 2.5s, the high-probability, but low-contiguity cause A was seen as equally strong as the low-probability, but high-contiguity cause B, and both reliably stood out compared to the remaining two non-contingent distracter items. This apparent trade-offbetween contingency and contiguity, rooted in contrasting two of David Hume’s (1739/1888) fundamental cues to causality, has important implications for psychological and statistical models of causal discovery, learning theory, and artificial intelligence.