Song preferences predict the quality of vocal learning in zebra finches

Curiosity constructs communicative competence through social feedback loops

One of the most important challenges for a developing infant is learning how best to allocate their attention and forage for information in the midst of a great deal of novel stimulation. We propose that infants of altricial species solve this challenge by learning selectively from events that are contingent on their immature behavior, such as babbling. Such a contingency filter would focus attention and learning on the behavior of social partners, because social behavior reliably fits infants' sensitivity to contingency. In this way a contingent response by a caregiver to an immature behavior becomes a source of learnable information - feedback - to the infant. Social interactions with responsive caregivers afford infants opportunities to explore the impacts of their immature behavior on their environment, which facilitates the development of socially guided learning. Furthermore, contingent interactions are opportunities to make and test predictions about the efficacy of their social behaviors and those of others. In this chapter, we will use prelinguistic vocal learning to exemplify how infants use their developing vocal abilities to elicit learnable information about language from their social partners. Specifically, we review how caregivers' contingent responses to babbling create information that facilitates infant vocal learning and drives the development of communication. Infants play an active role in this process, as their developing predictions about the consequences of their actions serve to further refine their allocation of attention and drive increases in the maturity of their vocal behavior.

Oxytocin receptor antagonism during early vocal learning reduces song preference and imitation in zebra finches

In species with vocal learning, acquiring species-typical vocalizations relies on early social orienting. In songbirds, for example, learning song requires dynamic social interactions with a "tutor" during an early sensitive period. Here, we hypothesized that the attentional and motivational processes that support song learning recruit the oxytocin system, which is well-understood to play a role in social orienting in other species. Juvenile male zebra finches naïve to song were each tutored by two unfamiliar adult males. Before exposure to one tutor, juveniles were injected subcutaneously with oxytocin receptor antagonist (OTA; ornithine vasotocin) and before exposure to the other, saline (control). Treatment with OTA reduced behaviors associated with approach and attention during tutoring sessions. Using a novel operant paradigm to measure preference while balancing exposure to the two tutor songs, we showed that the juveniles preferred to hear the song of the control tutor. Their adult songs more closely resembled the control tutor's song, and the magnitude of this difference was predicted by early preference for control over OTA song. Overall, oxytocin antagonism during exposure to a tutor seemed to bias juveniles against that tutor and his song. Our results suggest that oxytocin receptors are important for socially-guided vocal learning.

Machine learning and statistical classification of birdsong link vocal acoustic features with phylogeny

Birdsong is a longstanding model system for studying evolution and biodiversity. Here, we collected and analyzed high quality song recordings from seven species in the family Estrildidae. We measured the acoustic features of syllables and then used dimensionality reduction and machine learning classifiers to identify features that accurately assigned syllables to species. Species differences were captured by the first 3 principal components, corresponding to basic frequency, power distribution, and spectrotemporal features. We then identified the measured features underlying classification accuracy. We found that fundamental frequency, mean frequency, spectral flatness, and syllable duration were the most informative features for species identification. Next, we tested whether specific acoustic features of species' songs predicted phylogenetic distance. We found significant phylogenetic signal in syllable frequency features, but not in power distribution or spectrotemporal features. Results suggest that frequency features are more constrained by species' genetics than are other features, and are the best signal features for identifying species from song recordings. The absence of phylogenetic signal in power distribution and spectrotemporal features suggests that these song features are labile, reflecting learning processes and individual recognition.