Provides data indicating that development occurs in cycles, with behavioral competencies appearing and developing and then disappearing only to reappear again in a more complex form at a later age. Data on conservation and auditory-manual coordination in infancy are used to support this theory. (ED)

Reports on development of a model for studying communicative competencies using naturalistic observations of specific behaviors. Discussion focuses on ways mothers and toddlers train each other to be successively more effective in their relationships. (ED)