Judgement of two causal candidates from contingency information: II. Effects of information about one cause on judgements of the other cause

Abstract

When judgements are being made about two causes there are eight possible kinds of contingency information: occurrences and nonoccurrences of the outcome when both causes are present, when Cause 1 alone is present, when Cause 2 alone is present, and when neither cause is present. It is proposed that contingency information is used to some extent to judge proportionate strength, which is the proportion of occurrences of the outcome that each cause can account for. This leads to a prediction that judgements of one cause will be influenced by information about occurrences, but not nonoccurrences, of the outcome when only the other cause is present. In six experiments consistent support was found for this prediction when the cause being judged had a positive relation with the outcome, but no consistent tendency was found when the cause being judged had a negative relation with the outcome. The effects found for causes with positive contingency cannot be explained by the Rescorla–Wagner model of causal judgement nor by the hypothesis that causal judgements are based on conditional contingencies.

Notes

Causal powers are ultimately grounded in the natures of things. Similarly, our attributions of causal powers to things can be based on our knowledge of their physical properties. For example, if we come across a type of object that we have never encountered before we might still attribute to it the causal power to break vases on the basis of information about relevant physical properties such as mass, density, and rigidity (White, in press).

In the causal powers theory the term “causal power” refers specifically to the capacity of a material particular to produce a specific effect (White, 1989). The term was later used in the power PC theory (Cheng, 1997; Novick & Cheng, 2004), where it is defined as follows: “causes influence the occurrence of an effect, either producing or preventing it, with certain theoretical probabilities, termed causal powers” (Novick & Cheng, 2004, p. 459, original emphasis). These definitions differ in that the former refers to capacities and the latter to probabilities.

I am deeply grateful to the mathematical skills and endless patience of John Pearce, who enabled me to generate the values reported here.