Crow experiments suggest switching to vocal communication requires extra mental effort

For animals that can produce vocalizations, choosing to emit a sound involves various neural processes. For instance, it entails controlling when to emit a sound and how loud and high-pitched the sound will be, while also adaptively switching between vocalizations and other behaviors in response to changing circumstances.

Researchers at the University of Tübingen recently carried out a study exploring the control processes via which carrion crows (Corvus corone), birds belonging to the corvid family, switch between vocalizations and pecking behavior. Their findings, published in Proceedings of the Royal Society B, suggest that while crows can flexibly alternate between calling and pecking, switching to calling places greater demands on their brains.

"Crows are remarkably good at vocal communication," Diana A. Liao, first author of the paper, told Phys.org. "They can control when to make a sound and even 'count out loud.' This control over vocal production appears rare in animals, and it is a critical part of what allows us, humans, to speak fluently. What we didn't know was whether making a vocalization takes more effort than other motor actions, and this is the general question we set out to address."

Training crows to switch between calls and pecking

Liao and her colleagues carried out a series of experiments involving two male carrion crows raised in large indoor aviaries at the University of Tübingen. These crows were trained to either make a call or peck at a screen, depending on the visual cue presented to them at a given time.

"Crows were very good at both vocalizing and pecking, performing with high accuracy for all sequence types," said Liao. "However, making a vocalization took longer and the responses were more variable compared to pecking."

The researchers presented cues to crows following three distinct sequence types. These included random cue sequences, alternating sequences and blocks of 10 trials eliciting one response type.

"This let us see what happens when the crows need to switch between the two actions, and how predictable those switches are," explained Liao. "We then compared how fast and accurately the crows responded on trials where they switched responses compared with when they repeated the same response."

Switching between activities can come at a cost

The researchers observed that both crows could learn to flexibly switch between vocalizations and pecking. However, switching to calling slowed their responses compared to repeating a call, while switching to pecking had little effect on their response time. This suggests that vocal responses were associated with additional cognitive control demands.

"We observed vocal-specific switch costs," said Liao. "Switching is interesting because in humans and monkeys, changing from one task to another usually slows us down. This is thought to reflect the effort it takes to 'shift gears.' We found the same effect in crows, but only when they switch into making a vocalization after making a peck. This suggests that making a vocalization is more effortful for the crow than pecking."

This study introduces a promising experimental paradigm for investigating vocal control in crows and potentially other birds. Its findings could soon inspire further studies investigating the effort required to switch to calling in a broader range of species. In addition, their experimental methods could be combined with brain imaging tools to shed light on the neural processes supporting bird vocal control.

"The implication of our findings is that crows combine speed, accuracy and executive control over their vocal production, and this may help explain how flexible communication evolved," added Liao. "We are interested in further characterizing switch costs for different types of vocalizations. We would also like to examine the neural mechanisms that support switching between producing a vocal response and a pecking response."

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