Revisiting the Acquisition of Conditionals: Children's and Adults' Expression of Hypothetical Thought

Children produce conditional if-clauses later than other complex constructions, but the source of this delay is debated. On the conceptual complexity explanation, children acquire if-clauses later than other morphosyntactically similar constructions because they are cognitively more complex. On the pragmatic overlap explanation, children produce if-clauses infrequently because other, simpler constructions can convey similar conditional meanings. We tested the two explanations experimentally by eliciting hypothetical language in 3- to 6-year-old children and adults. Children and adults expressed hypotheticality through a variety of grammatical constructions, beyond if-clauses, in accordance with the pragmatic overlap explanation. Across age groups, if-clauses were not delayed compared to other similar constructions, against the conceptual complexity prediction. Still, the data showed important developmental differences: 3- and 4-year-old children rarely expressed conditional meanings, whereas 5- and 6-year-olds were adult-like. These findings suggest that expressing hypothetical thought develops substantially during the preschool years through interacting cognitive, pragmatic, and linguistic factors.