It’s no secret that corvids are capable of amazing feats of creative and intelligent thinking, but the newly discovered ability has us amazed.
A team of scientists has shown that crows can ‘count’ out loud – producing a specific and deliberate number of crows in response to visual and auditory stimuli. While other animals such as bees have demonstrated the ability to understand numbers, this specific display of numeracy has not yet been observed in any other non-human species.
“Producing a specific number of vocalizations with a purpose requires a sophisticated combination of numerical abilities and vocal control,” writes a team of researchers led by neuroscientist Diana Liao of the University of Tübingen, Germany.
“Whether this ability exists in animals other than humans is not yet known. We have shown that crows can flexibly produce variable numbers of one to four vocalizations in response to arbitrary stimuli associated with numerical values.”
The ability to count aloud is different from understanding numbers. It requires not only understanding, but purposeful control of the voice with the goal of communication. Humans are known to use speech to count numbers and communicate quantities, a skill learned by the young.
When toddlers are learning to count, learning specific numbers associated with specific quantities can take time to master. Meanwhile, children can sometimes use random numbers to make a voice recording. Instead of counting “one, two, three”, they may say “one, one, four” or “three, ten, one”. The number of vocalizations is correct, but the words themselves are scrambled.
The biological origins of symbolic counting are unknown, but since crows are known to understand difficult numerical concepts such as zero, Liao and colleagues thought they represented a good candidate for investigating more sophisticated number skills.
They conducted their study on three common crows (Corvus corone), which the researchers trained to produce a variable number of vocalizations, between one and four, after being shown an arbitrary symbol or sound stimulus. Once the crows had produced the required number of cows, they had to peck at a target to indicate they were done.
The researchers found that all three crows were able to produce the correct number of cows in response to the stimuli, with the occasional error usually appearing as one cow too many or too few.
The researchers say this is similar to the way human toddlers count, using a non-symbolic approximate number system that is planned in advance before the first vocalization.
Interestingly, the timing and sound of the first vocalization in the sequence was associated with how many vocalizations were made subsequently, and each vocalization in the sequence had acoustic properties specific to its place in the sequence.
This feat is particularly impressive for crows, as intentional vocalizations are more difficult to produce and have longer reaction times than pecking or head movements, for example.
It could represent a previously unknown channel for avian communication in the wild. For example, chickens make more “dee” sounds in their alarm calls to larger predators.
“Our results show that crows can flexibly and intentionally produce an ordered number of vocalizations using the ‘approximate number system,’ a non-symbolic number estimation system shared by humans and animals,” the researchers write in their paper.
“This competence in crows also reflects the numeracy skills of toddlers before they learn to understand basic number words, and may therefore represent an evolutionary precursor to true counting, where numbers are part of a combinatorial symbol system.”
The research was published in Science.