There was a significant decrease in the prevalence of impulsive choices with age: 35.0 and 27.5% of the sample preferred the smaller but immediate reward at ages 12 and 14, respectively (McNemar’s test: (χ2 = 8.45, df = 1, P = .004). There were no significant sex differences in the preference of immediate versus delayed rewards at either age (χ2 = .60 and .46, P = .44 and P = .50 at ages 12 and 14, respectively). There was a highly significant within-subject association between choices made at ages 12 and 14 (χ2 = 33.9, df = 1, P < .0001; tetrachoric r = .44) indicating significant developmental stability of temporal discounting preferences despite significant age-related changes.
