Conditional probability and pragmatic conditionals: Dissociating truth and effectiveness

Recent research (e.g., Evans & Over, 2004 Over, D. E., Manktelow, K. I. and Hadjichristidis, C. 2004. Conditions for the acceptance of deontic conditionals. Canadian Journal of Experimental Psychology, 58: 111–120.  [Google Scholar]) has provided support for the hypothesis that people evaluate the probability of conditional statements of the form if p then q as the conditional probability of q given p, P(q/p). The present paper extends this approach to pragmatic conditionals in the form of inducements (i.e., promises and threats) and advice (i.e., tips and warnings). In so doing, we demonstrate a distinction between the truth status of these conditionals and their effectiveness as speech acts. Specifically, while probability judgements of the truth of conditional inducements and advice are highly correlated with estimates of P(q/p), their perceived effectiveness in changing behaviour instead varies as a function of the conditional probability of q given not-p, P(q/～p). Finally, we show that the conditional probability approach can be extended to predicting inference rates on a conditional reasoning task.     

Everyday reasoning with inducements and advice

In two experiments, we investigated how people interpret and reason with realistic conditionals in the form of inducements (i.e., promises and threats) and advice (i.e., tips and warnings). We found that inducements and advice differed with respect to the degree to which the speaker was perceived to have (a) control over the consequent, (b) a stake in the outcome, and (c) an obligation to ensure that the outcome occurs. Inducements and advice also differed with respect to perceived sufficiency and necessity, as well as the degree to which these statements were perceived to be effective in changing the behaviour described in the antecedent of the conditional. Multiple regression analyses indicated that perceived control over the consequent, necessity, and sufficiency emerged as the best predictors of (a) the degree to which statements were perceived to be effective in changing the behaviour of the addressee, and (b) inference patterns on a conditional arguments task.