Mental Terms and the Development of Certainty.

MOORE, CHRIS; BRYANT, DANA; and FuRRow, DAVID. Mental Terms and the Development of Certainty. CHILD DEVELOPMENT, 1989, 60, 167-171. In the present study, we examined children's understanding of the pragmatic function of mental terms to express relative certainty. 69 children between the ages of 3-1 and 8-11 were presented with contrasting pairs of statements by 2 puppets. Different trials contained all the possible pairwise combinations of the terms know, think, and guess. On the basis of what they heard, children were required to find an object hidden in 1 of 2 places. Results showed a significant improvement with age for the know-think and know-guess contrasts, but no improvement with age for the think-guess contrast. By 4 years of age, know was differentiated from think and from guess. In both cases, know was chosen as a more reliable indicator of the location of the object. Further improvement occurred for both contrasts involving the word know between 4 and 5 years of age, so that by 5 years, performance had reached asymptote. These results demonstrate the development of pragmatic competence with mental terms over the preschool period and may also indicate the appearance of the mental state concept of certainty.