Temporal variability enhances the acquisition of stereotyped communication signals

Abstract

Species-typical behaviors are organized into species-typical patterns, and deviations away from these patterns often diminish the strength of behavioral and sensory responses to such stimuli. In songbirds like the zebra finch, species-typical songs consist of acoustic elements (syllables) arranged into stereotyped (i.e., highly predictable) sequences with stereotyped timing. However, the degree to which deviations away from these stereotyped temporal patterns modulate the strength of vocal learning (i.e., the fidelity of vocal imitation) remains unknown. Here we tutored 123 juvenile zebra finches with stimuli that varied in the stereotypy of syllable sequencing and timing. In contrast to the prediction that deviations away from species-typical stereotypy would diminish vocal learning, deviations from sequence or timing stereotypy did not decrease how well juveniles imitated the acoustic structure of syllables. Moreover, presenting syllables in species-atypical sequences (i.e., randomized syllable sequences) enhanced vocal imitation in birds that were tutored later in development. This unexpected enhancement of birdsong learning by sequence variability resembles the effects of contextual diversity on speech acquisition and indicates that such variability can benefit learning even for very stereotyped behaviors.