Conversations with friends have an ease that is hard to replicate with someone you have just met – often replies come more naturally and timing just seems to click. A strikingly similar pattern plays out in zebra finches, very sociable songbirds whose back-and-forth chatter with familiar individuals can take a noticeably different rhythm to exchanges with strangers. Now, researchers at the Max Planck Institute for Biological Intelligence have uncovered how this communication pattern is reflected in the brain, showing that social context influences the activity of neurons involved in vocal communication.
Innate flexibility
Zebra finches are one of the most widely studied songbirds in neuroscience, partly because they are one of the few animal species that, like humans, learn to vocalize by listening to others. Much of this research has focused on their songs, which males learn by copying adults. However, zebra finches also produce short contact calls in the form of simpler sounds that, unlike songs, the birds are born knowing how to make.
Previous studies have shown that when using these calls in social exchanges, the birds tend to contact call more often and more consistently with individuals they are familiar with. But what happens in the brain when a bird hears a familiar call, and how that might shape its reply, remained unclear. A team led by senior researchers Daniela Vallentin and Jonathan Benichov set out to find answers.
The team played zebra finches recordings from familiar and unfamiliar birds, and the birds replied more often, faster, and more consistently to familiar calls. When the team then studied what was happening in the brain, they found a clear neural counterpart.
“We have found that when zebra finches hear a familiar call, their brains respond differently to one from an unfamiliar bird,” says Carlos Gomez-Guzman, doctoral researcher and first author of the study, published in PLOS Computational Biology . “One of the things that surprised us was the sheer scale of the neuronal response: more than 70% of neurons in HVC, a region involved in controlling vocal timing, responded when birds heard a call — showing this region is not just involved in song, but is actively processing social calls too. Within that broad response, neurons called inhibitory interneurons, which help regulate whether and when a bird calls back, fired more strongly and for longer when the caller was familiar. It is not that calls from familiar birds sound particularly different, but when they recognise the call of an acquaintance the social bond between the birds is reflected in how the brain responds.”
How the brain tunes in
Zebra finches make for a fascinating window into vocal exchanges: like human speech, replies between birds typically follow in less than half a second. However, unlike us each bird’s contact call is something it’s born with and cannot reshape – what varies is when and how quickly it calls back.
To find out what was happening in the brain, the team recorded neuronal activity while birds listened to familiar and unfamiliar calls. HVC contains two key types of neurons – excitatory projection neurons, which send signals to other brain regions involved in song and vocal production, and inhibitory interneurons, which act locally, and can influence whether and when a bird initiates a call. Both types of neurons responded upon hearing any call, however interneurons showed a much higher sensitivity to familiarity, firing more intensely and for longer when the caller was known. This neural activity persisted into the window when a bird would normally reply, suggesting it could influence when the bird calls back.
“The strength of this neural activity closely matched how quickly and reliably the birds replied, and using machine learning to study the data we could even distinguish familiar from unfamiliar callers based on interneuron activity alone,” says Gomez-Guzman. “The study shows it is not just learned song that can be flexibly adjusted in communication – behaviors like contact calling, which birds such as zebra finches are born with, can be too”. That opens up fascinating questions: is this precise social timing itself something birds learn? How do these neurons interplay with those in other, evolutionarily older brain regions? Understanding how zebra finches manage this could shed light on why some species are so much better at vocal exchanges than others, and even give insights into the cognitive demands of holding a conversation – something we take for granted, but which requires the brain to listen, decide, and respond in a split second.
PLOS Computational Biology
Experimental study
Animals
Social familiarity strengthens neural and vocal responses to conspecific calls in zebra finches
11-Mar-2026