Early extensional intuitions about probability
Vittorio Girotto
University IUAV of Venice, Italy;
CNRS-University of Provence, Aix-en-Provence, France;
In this paper, we present the results of a series of studies aimed to show that young
children possess an elementary competence about probability. Following the hypothesis
that naïve individuals can assess probabilities extensionally, by considering the possible
ways in which events may occur (see Johnson-Laird et al, 1999: Girotto & Gonzalez,
2001), we conducted a series of experiments in which children of various ages tackled
decision-making problems, the solution of which implied correct probability evaluations.
The main result is that from the age of six children solve these problems, even in
conditions in which choosing the more probable option implies a comparison of
proportions in sets of different sizes (i.e., an ability that the traditional Piagetian view
considers as a hallmark of adolescent and adult thinking). In a related series of studies,
we showed that from the age of six children are also able to evaluate conditional
probabilities in an extensional way, and to update their evaluations in the light of new
evidence. Finally, we also proved that from the age of nine children solve problems
calling for a combinatorial analysis of possibilities. The latter findings contradicts the
views according to which only adolescents and adults can use combinatorial procedures
to assess probability. Taken together, the reported results corroborate the hypothesis that
naïve probabilistic reasoning is grounded on basic extensional intuitions.