ACTION-BASED LEARNING - A NEW FORM OF DEVELOPMENTAL PLASTICITY IN BIRD SONG

Two forms of developmental plasticity in bird song are contrasted. The classical 'memory-based' or sensorimotor process includes a sensory phase during which a song model is memorized followed by a motor phase during which the bird matches his own song to the model via auditory feedback. In contrast, 'action-based learning' refers to the selection of songs that are already produced for retention in the mature repertoire. Evidence for action-based learning appears in the form of a large (overproduced) repertoire of songs in the plastic phase of song development. During the transition from plastic to crystallized song, social interactions selectively reinforce performance of certain song types, while non-reinforced song types are discarded. We review evidence from three species of sparrow which suggests that song sharing among territorial males, a common form of vocal plasticity usually thought to solely involve memory-based learning, may be the result of action-based learning. These forms of song learning are complementary in that memory-based learning provides the raw song material upon which the selective forces of action-based learning act. We suggest that action-based learning may be widespread among behaviour patterns that involve overproduction of motor patterns in youth.