Evaluation strategies for some nonstandard conditionals during adolescence.

380 adolescents and young adults between the ages of 11 and 29 years participated in three experiments in which they were asked to evaluate both universally quantified nonstandard and standard conditionals using items of information bearing upon them. Subjects found it much easier to avoid a biconditional interpretation with the nonstandard than with the standard conditionals, which throws doubt on the explanation of desire for symmetry of biconditional conversion. It was argued, from data of other studies, that a modified version of the Piagetian view that biconditional conversion occurs as a result of a desire to avoid the complications of dealing with three factors explains most cases of such conversion in adolescence. Results also confirmed that it is more profitable to analyse performance on tasks of this kind using a two-stage model of interpretation and information use previously developed to explain performance with standard universally quantified conditionals than to view such tasks as providing truth-table values. Such an analysis was extended to the nonstandard conditionals studied in the present paper. The origins of the dramatic differences in information-use strategies adopted by adolescents for standard and nonstandard conditionals remain unclear.