DISCONTINUOUS AND INCREMENTAL PROCESSES IN THE SONG LEARNING OF BIRDS- EVIDENCE FOR A PRIMER EFFECT

Studies on the song learning in birds revealed a puzzling property of the acquisition system: Stimulus memorization becomes effective after remarkably few exposures, but nevertheless shows a relationship to the frequency of exposure to learning stimuli. This raises questions on t he amount of learning that will occur during a given exposure to song. To examine this issue, we tutored handraised fledgling nightingales ( Luscinia megar hynchos) with song strings, in which the serial success ion of species-typical master songs was altered upon subsequent exposu res. The sequencing of imitations obtained from the birds' adult singi ng revealed the following results: (1) A single exposure was sufficien t for subjects to acquire serial information on song-type sequencing. (2) The first exposure to a master string played a key role for this a ccomplishment. (3) Nevertheless, the acquisition of serial information improved with increasing exposure frequency of master strings. (4) Th e acquisition of song patterns was not impaired by a non-regular prese ntation of master song-types. With respect to the particular salience of the first exposure for sequence memorization, we termed the phenome non 'primer effect'. The findings suggest that stimulus acquisition du ring perceptual song learning is mediated by a discontinuous process. Once acquired, information is then consolidated gradually, i.e. throug h an incremental process.