Development of role-differentiated bimanual manipulation in infancy: Part 2. Hand preferences for object acquisition and RDBM--continuity or discontinuity?

This second paper in a series of three investigated the development of hand preference for role-differentiated bimanual manipulation (RDBM) relative to the infant's hand preference for object acquisition and to the infant's hand-use for acquiring the objects used to assess RDBM. The same 90 infants (30 with a right preference, 30 with a left preference, and 30 with no preference to acquire objects) from the first paper were tested from 9 to 14 months for hand preference for acquiring those objects used to assess RDBM and for a hand preference for RDBM. Multilevel analysis revealed that infants with a hand preference for acquiring objects decreased in their use of the preferred hand for object acquisition during the 11 to 14 month interval, which coincided with the development of a hand preference for RDBM. These results are discussed in relation to the cascade theory of hand preference development.