Do crows know how to count out loud?

Counting out loud, for example, reciting “one, two, three,” requires understanding of numerical quantities and intentional vocal control. Humans use speech to symbolically count and communicate quantities, a complex skill that develops in childhood.

Before mastering symbolic counting, where specific words are related to specific quantities, young children often produce a number of speech sounds that match the number of objects they see, using these sounds as acoustic markers to convey the corresponding number.

This early behavior in humans reflects non-symbolic competencies shared with animals.

Several animals have demonstrated their ability to discriminate between different numbers of objects and to transmit information through different numbers of vocalizations. However, there has been persistent doubt as to whether non-human animals have the ability to “count” by deliberately producing specific numbers of vocalizations.

Diana A. Liao’s team at the University of Tübingen in Germany set out to find out. To that end, she and her colleagues investigated whether black crows (Corvus corone) – one of the few bird species that possesses both numerical competence and control volitional vocal – can control the number of vocalizations they emit to solve complex vocal response tasks.

A raven. (Photo: Donna Dewhurst / US Fish and Wildlife Service / US Geological Survey)

Liao and colleagues trained three crows to produce one to four vocalizations in response to both visual (colored number) and auditory (distinctive sound) cues, which were associated with numerical values.

On each trial, the crows had to produce a target number of vocalizations and indicate the end of the vocal sequence by pointing to a target with their beak.

The study’s authors found that crows could successfully and deliberately produce specific numbers of vocalizations in response to specific cues, a degree of control not yet observed in other animals.

Consistent with these findings, the birds used an approximate non-symbolic number system, planning the number of vocalizations before beginning.

Further analysis showed that the timing and characteristics of the initial vocalization predicted the number of subsequent vocalizations, and different acoustic features in the vocalizations indicated the “number” within a given sequence.

“This competence in crows also reflects the numbering skills of young children before they learn to understand words relating to cardinal numbers and may therefore constitute an evolutionary precursor to true counting where numbers are part of a system of combinatorial symbols,” argue Liao and his colleagues.

The study is titled “Crows ‘count’ the number of self-generated vocalizations.” And it has been published in the academic journal Science. (Source: AAAS)