Everyday statistical reasoning during adolescence and young adulthood: motivational, general ability, and developmental influences.

Research on adolescent problem solving was extended into the domain of statistical reasoning and potential biases in reasoning. In Experiment 1, adolescents solved everyday reasoning problems dealing with the "law of large numbers" and the "intuitive analysis of covariance." In each problem, evidence was presented that portrayed each participant's dominant career goal favorably or unfavorably. In Experiment 2, adolescents and young adults were presented "law of large numbers" evidence that was goal-threatening, goal-enhancing, or goal-neutral. In both experiments, statistical reasoning could be used to discredit the evidence. Results indicated that (1) adolescents and young adults found goal-enhancing evidence more convincing than goal-neutral evidence which, in turn, was perceived more favorably than goal-threatening evidence; (2) statistical reasoning was more frequent on goal-threatening problems than on goal-neutral and goal-enhancing problems; (3) intellectual ability was unrelated to the biases in adolescents' reasoning; (4) verbal ability was linked to "law of large numbers" reasoning, but no cognitive ability was systematically correlated with "analysis of covariance" reasoning; and (5) law of large numbers reasoning of young adults was superior to that of adolescents, but young adults were no less biased in their reasoning than adolescents. The potential functions and consequences of adolescents' biased reasoning, the relation of everyday reasoning to general intellectual abilities, and the influences of motivation and depth of processing are discussed.