A study of the probabilistic prediction in adolescents under conditions of presentation of sygnals with different probabilities has revealed three types of prognostic activities similar to those characteristic of adult subjects: 1) prevalence of choices of highly probable events, 2) probabilistic correspondence of predictions and events, 3) prediction of alternative events on the basis of equal probabilities. Comparison of subjects differing by the parameter "strength-weakness of the nervous system" shows that "strong" subjects tend to make probabilistic preditions of the first type, "middle" subjects tend to predictions of the second type, and "weak" - to the third type.