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. SIGNIFICANCE STATEMENTLittle is known about the degree to which the temporal patterning of acoustic elements ("syllables") modulates vocal learning and imitation. We tested the contribution of temporal variability in syllable sequencing and timing, hypothesizing that deviations away from species-typical stereotypy (predictability) in syllable sequence and timing patterns would diminish the strength of vocal learning. In contrast to our predictions, deviations from sequence and timing stereotypy did not decrease vocal learning. Moreover, presenting syllables in random sequences enhanced vocal imitation in birds that were tutored later in development. This unexpected finding highlights that sequence complexity can potentiate vocal learning in individuals with more developed vocal control, resembling how complexity and ability interact to modulate various forms of learning in humans.