Biologists have long debated whether animals process the meaning of vocalizations or simply react instinctively. A new study from neuroscientists at the University of California, Berkeley, provides evidence that zebra finches do form mental representations of meaning when they hear calls from their peers.
The research, led by Julie Elie and Frédéric Theunissen, found that zebra finches categorize calls in a way similar to humans. Both species group calls into about a dozen distinct types used for alarms, identification, courtship, distress, hunger, or aggression. However, the birds were sometimes confused by calls with similar meanings even if they sounded different.
Julie Elie explained: “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 added: “We have shown, indirectly, that birds understand what they are saying.” He also noted: “This is also the first time anyone has ‘actually tested whether animals agree with the human experts that calls have different meanings’ and that the acoustic differences humans detect are also recognized by the birds.”
The findings suggest even small-brained birds like zebra finches possess a cognitive understanding of communication rather than merely reacting reflexively. According to Elie: “If a small bird like the zebra finch has a mental representation of meaning…birds such as crows…likely have an even more elaborate perceptual landscape.” She is now working with researchers in France to investigate how mice represent vocalizations mentally.
Zebra finches serve as important models for studying vocal learning because young males learn mating songs similarly to how humans learn speech. Theunissen has spent decades researching how these birds process sounds and develop auditory perception through both social and sound experience.
Elie cataloged 11 distinct vocalizations among captive zebra finches and associated each with specific behaviors through detailed observation. In an experiment where birds had to identify rewarded call-types among thousands played randomly, she found their responses matched human categorization.
“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.’”
The researchers discovered that mistakes made by finches in identifying calls were more often due to similarities in meaning than sound—a sign of cognitive processing rather than automatic reaction.
“Birds have various degrees of intelligence…But in terms of auditory discrimination while doing this task, they are really quite phenomenal,” Theunissen said.
By analyzing brain activity during these tasks, Elie and Theunissen hope to pinpoint where and how meaning is represented neurologically. As Theunissen described: “Now we’re going from sensation to perception…Perception is like assigning a label…Or here, ‘I understand what you’re speaking.’”
Coauthors on this study include Aude de Witasse-Thézy (University de Lyon) and Logan Thomas and Ben Malit (UC Berkeley). Their work was published in Science and funded by the National Institutes of Health (R01DC018321).
“By studying vocal communication, we get a better sense of the cognitive ability of animals,” Elie said. “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.”
Related resources include information on categorical and semantic perception in zebra finch calls (https://www.science.org/doi/10.1126/science.adk1732) and details about ongoing research at Theunissen’s lab (https://theunissenlab.berkeley.edu/).
