NJIT Researcher Examines Birds' Vocal Development With Virtual Tutors

In the highly social world of the zebra finch, every male has a unique song: a brief motif resembling the squeak of a mechanical toy that he chirps, often in rapid succession, in courtship and communal gatherings. These songs are not innate. Pubescent finches develop their signature sound by listening to adult male birdsong which they then individualize with subtle variations in frequency, tonality and rhythm.

In Julia Hyland Bruno’s research, fathers have been replaced by virtual tutors in laboratory-based studies designed to examine the birds’ vocal development under controlled conditions. In one type of experiment, the young finches have a device in their cage with a red button that, when pressed with their beaks, releases the pre-recorded song of a mature adult. They are given the freedom to activate it whenever they like; some tap over and over, while others pause more frequently.

“There is such variability in these self-lessons: when and how often the birds listen and whether they vocalize with the recordings. How often they play the song gives us an indicator of how motivated they are to learn,” says Hyland Bruno, an assistant professor of humanities and social sciences who studies communication development in animals. She adds that marked fluctuations in demand for song playbacks — quiet periods and sudden bursts of activity — coincided with vocal changes, such as the emergence of new song syllables.

Hyland Bruno is interested in the roles that self-teaching and social interaction play in language development across species, particularly as digital devices encroach on spoken and nonverbal exchanges and attention more generally.

“Digital technologies are rapidly altering the ways we relate to one another across both space and time, from the reach and topology of our social networks to the rhythms of our social interactions,” she says. “We know social interactions are important to early language development, and I’m interested in what it’s like to grow up and learn how to communicate in such an environment.”

For zebra finches, birdsong is part of a dynamic communication system which also includes innate vocalizations that birds of both sexes use to maintain contact with each other, coordinate parental care and express aggression. Male song is not territorial and song “lessons” require interactions between pupil and tutor, unlike certain other species where birds pick up their songs simply by listening to adults around them.

To better observe these interactions, she’s developing a model system, initially focused on birds, to study the effects of vocal interactivity. In the next phase of her studies, she’s building a virtual bird that will initiate songs and also respond to the young bird. It will allow her to observe the impact of varied response scenarios: adults that sing proactively, reply quickly, pause at length before answering or don’t respond at all.

“In this controlled environment, where we mimic the natural system, but also perturb it, we can study what happens when we alter the learning environment, by introducing, for example, the extremes of high interactivity and non-responsiveness,” she explains. “We know that isolated birds with no tutors develop a song, but it is atypical and generally not accepted by other birds. But we don’t know how early social interactions might affect birds’ ability to communicate as adults.”

Young birds begin to babble when they leave the nest, but it takes months for the song to achieve a repeatable structure. Their song crystallizes at sexual maturity, with no further changes thought to occur. However, Hyland Bruno and her colleagues have observed subtle vocal changes beyond this “sensitive period” for vocal learning, including added ornamentation and changes in rhythm, that seem to depend on different social contexts. Indeed, adults familiar with each other may align the pitch and tone of their songs in the way people adapt to others’ speech, immediately repeating catchy words and adjusting their intonation, volume and phrasing.

She intends to study the interactions of the laboratory-trained birds as adults to try to understand the downstream effects of their early development under varying conditions.

Hyland Bruno says she is also interested in the ways in which language development relies on elemental, nonverbal cues, such as tone of voice, rhythm and responsiveness, and how technology may be disrupting these patterns.

Technology, including screen time, is changing the dynamics of our interactions in significant ways, she notes. Digital devices are causing more distraction, for example, as parents spend more time on them and less time paying attention to developing infants and, while immersed in devices, may respond to them more slowly or less fully.

“Bird studies are useful,” Hyland Bruno says, “because they allow us to process how communication develops in individuals and how patterns are transmitted across generations. We can alter learning conditions in ways that would be unethical in humans.”