New research from the University of California, Berkeley indicates that zebra finches do not simply react reflexively to each other’s calls but actually process and understand their meaning. The study, led by neuroscientists Julie Elie and Frédéric Theunissen, suggests that these birds categorize vocalizations in a way similar to humans.
The researchers found that zebra finches organize their calls into about a dozen distinct types, or “words,” which serve different functions such as sounding alarms, signaling identity and location, courtship, distress, hunger, or aggression. Despite acoustic differences between some calls, the birds sometimes confuse those with similar meanings more often than those that sound alike but have different meanings.
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 a level of cognitive processing in vocal communication among zebra finches. Elie said: “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 collaborating on related research involving mice.
The research team designed experiments where captive zebra finches listened to recordings of various call types and were rewarded for identifying specific ones associated with food. Their responses indicated agreement with human categorizations of call types.
Elie described her approach: “This tells us that they agree with whatever organization of the repertoire we made…The human is here observing and saying, ‘Those are your words.’ And the bird is saying, ‘Yes, these are my words.’”
Theunissen commented on their capabilities: “Birds have various degrees of intelligence…But in terms of auditory discrimination while doing this task, they are really quite phenomenal.”
To further test understanding versus reflexive reaction, researchers analyzed mistakes made by birds during discrimination tasks. They found mistakes were based more frequently on semantic similarities than on acoustic ones.
Elie summarized: “By studying vocal communication, 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.”
Ongoing work involves brain recordings during these tasks to locate where perception of meaning occurs within avian brains.
Other contributors include Aude de Witasse-Thézy from University de Lyon in France and Logan Thomas and Ben Malit from UC Berkeley.
For additional information about categorical and semantic perception in zebra finch communication or details about ongoing research projects at UC Berkeley’s Theunissen lab:
– Categorical and semantic perception of call types in zebra finch (Science): https://www.science.org/doi/10.1126/science.adl0485
– Theunissen lab website: https://theunissenlab.berkeley.edu/
