New research from the University of California, Berkeley, indicates that zebra finches interpret vocal calls with a level of understanding similar to how humans process language. The study suggests these birds do not simply react reflexively to sounds but instead mentally represent the meaning behind different calls.
The research team found that zebra finches organize their vocalizations into distinct categories or “words” used for various purposes such as sounding alarms, signaling identity and location, courting partners, or expressing distress and aggression. Despite some calls sounding quite different even to human listeners, the birds were sometimes confused by calls within the same semantic group—those with similar meanings—more often than by acoustically similar but semantically different calls.
Julie Elie, a research associate in UC Berkeley’s Department of Neuroscience and lead author of the study, said: “As long as call-types have clearly different meanings for the birds, they are very well distinguished even if their acoustics are quite similar. But call-types further apart in the acoustic space that can be lumped in the same semantic category are surprisingly mistaken more often by the bird. It’s proof that they have this mental representation of the meaning, which leads them to make errors. Otherwise, if this representation of meaning was not there, there’s no reason they would make errors more often between call-types that belong to the same semantic group.”
Frédéric Theunissen, professor of neuroscience at UC Berkeley and senior author on the paper published in Science on September 18th, added: “We have shown, indirectly, that birds understand what they are saying.” He noted it is also “the first time anyone has actually tested whether animals agree with the human experts that calls have different meanings” and whether birds recognize acoustic differences identified by humans.
The findings suggest complex vocal communication may exist beyond zebra finches; Elie commented that species like crows could possess an even more elaborate perceptual landscape due to their complicated vocalizations.
Zebra finches are widely studied because young males learn unique mating songs similarly to how humans acquire speech. This makes them valuable models for understanding vocal learning and auditory perception. Theunissen has previously demonstrated that both social interaction and sound exposure shape development in these birds’ auditory cortexes.
Elie cataloged 11 distinct zebra finch call types during her fieldwork in Australia and subsequent laboratory studies at UC Berkeley. She matched each call-type with specific behaviors through detailed observation. In experiments designed by Elie, captive zebra finches listened to randomized recordings drawn from thousands of individual bird calls; they learned to select particular rewarded call-types associated with seeds by pecking a button.
“This tells us that they agree with whatever organization of the repertoire we made,” Elie said. “The human is here observing and saying, ‘Those are your words.’ And the bird is saying, ‘Yes, these are my words.’”
According to Theunissen: “Birds have various degrees of intelligence… But in terms of auditory discrimination while doing this task, they are really quite phenomenal.”
Further analysis showed when mistakes occurred during these tasks; errors happened more frequently between semantically related calls rather than acoustically similar ones—a surprising result for researchers.
Elie explained one example involving two contact calls used under different circumstances: one (“tet”) exchanged quietly among nearby birds tracking each other’s location; another (“distance” call) is louder when individuals cannot see each other. Despite significant acoustic differences between these two contact calls compared to others like alarm signals (which sound similar), confusion most often arose within this semantic group.
“By studying vocal communication,” Elie said,“we get a better sense of the cognitive ability of animals… Maybe at one point we’ll be able to communicate with other animals. If we do the effort of really deciphering their language, we might be able to understand them better.”
The research team is now conducting brain recordings during discrimination tasks aiming to pinpoint where meaning is represented neurologically within zebra finch brains.
“Now we’re going from sensation to perception,” Theunissen said.“Perception is like assigning a label… Or here,’I understand what you’re speaking.’”
Other coauthors include Aude de Witasse-Thézy (University de Lyon), Logan Thomas (UC Berkeley), and Ben Malit (UC Berkeley). The work was funded by grants from the National Institutes of Health.
