This paper offers further evidence on the relation between task complexity and amount of transfer, using imbecile subjects. The main aim of the investigation was to determine whether transfer might occur between widely different tasks, requiring some degree of conceptual behaviour for their performance. The transfer task consisted of photographs of objects within five common categories; three different training tasks of varying complexity required the sorting of geometrical shapes. The two more complex of these training conditions resulted in considerable transfer on retest with the photographic material, and upon its subsequent direct acquisition. The simple geometric training gave results mid-way between the former and those of a control group. Transfer between widely different tasks has thus been demonstrated and the possible implications for understanding of the development of conceptual abilities are briefly considered.