Longitudinal study of the development of derived relations in an infant.

A normally developing child, Charlie (16 months old at the beginning and 27 months old at the end of this study), was tested several times for the derivation of relations over a period of 8 months. In a series of studies Charlie was: (1) taught to match names to pictures or pictures to names and was tested for derived relations of mutual entailment, (2) tested for retention of trained and derived relations after a 2 week delay and for the derivation of mutual entailment relations after a 1 week delay from training, (3) taught to match sounds to pictures and names to pictures and tested for mutual entailment relations and name-sound and sound-name combinatorial entailment relations, and (4) tested for the matching of a novel picture to a novel name ("nonverbal" exclusion) and for subsequent naming of the novel excluded picture ("verbal" exclusion). The results show that Charlie derived mutual entailment relations and showed nonverbal exclusion as early as 17 months. Combinatorial entailment relations and verbal exclusion emerged later. These findings lend support to the view that derivation of relations is not dependent upon sophisticated verbal abilities, and that such performances can be viewed as historically and contextually situated actions that develop over time.