Crows can “count” vocally up to four in response to cues, showing complex vocal control similar to young children.
Researchers have discovered that crows can control the number of vocalizations they produce, effectively “counting” up to four in response to cues. These findings indicate that crows are capable of using a non-symbolic number system and exhibit a level of vocal control similar to the early counting skills of human toddlers.
Toddler and Animal Counting Comparisons
Counting aloud, such as reciting “one, two, three,” requires understanding numerical quantities and deliberate voice control. Humans develop the ability to symbolically count and communicate quantities in early childhood.
Before mastering symbolic counting, where specific words relate to specific quantities, toddlers will often produce a number of speech sounds that match the number of objects they see, using these sounds as acoustic tallies to convey the corresponding number. This early behavior in humans reflects non-symbolic abilities also seen in animals.
Several animals can differentiate between varying quantities of objects and communicate through differing numbers of vocalizations. However, whether non-human animals have the ability to “count” by deliberately producing specific numbers of vocalizations remains unknown.
Research on Numerical Competence in Crows
A team of researchers led by Diana Liao investigated whether carrion crows (Corvus corone) – one of the few bird species possessing both numerical competency and volitional vocal control – can control the number of vocalizations they produce to solve complex vocal response tasks.
The researchers trained three crows to emit one to four vocalizations in response to visual (colored numerals) and auditory (distinct sounds) cues that were associated with numerical values. In each trial, crows had to produce a target number of vocalizations and indicate the end of the vocal sequence by pecking at a target.
Results and Implications
The study showed that crows could deliberately produce specific numbers of vocalizations in response to designated cues, a level of control not previously observed in other animals. According to the findings, the birds used a non-symbolic approximate number system, planning the number of vocalizations before starting.
Further analysis showed that the initial vocalization’s timing and features predicted the number of subsequent vocalizations, and different acoustic features in vocalizations indicated the “number” within a given sequence. “This competency in crows also mirrors toddlers’ enumeration skills before they learn to understand cardinal number words and may therefore constitute an evolutionary precursor of true counting where numbers are part of a combinatorial symbol system,” the researchers explained.
Reference: “Crows “count” the number of self-generated vocalizations” by Diana A. Liao, Katharina F. Brecht, Lena Veit and Andreas Nieder, 23 May 2024, Science.
DOI: 10.1126/science.adl0984
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