The findings are published in the journal *Communications Biology* and provide new insights into the evolution of communication as well as the perception biases of the human visual system.
Communication signals often evolve to match the perceptual capabilities of the receiving individuals, known as signal-receiver coevolution. Although these sensory biases have been studied extensively in vision and olfaction, little is known about how they affect vocal communication.
This research team used a comparative approach and measured how closely matched vocal communication signals are to the perceptual abilities of the receivers in the same species and in close relatives. They found that species with similar hearing abilities generally evolve more similar vocal communication signals, providing support for signal-receiver coevolution in vocal communication.
To determine the perceptual capabilities of 20 species of birds and primates, the researchers exposed the animals to a series of simple computer animations that moved on a computer screen. The animations varied in their speed and smoothness and were designed to exploit biases in the visual systems of primates.
The researchers measured the animals' responses to these animations using an eye-tracking device and found that the different species consistently differed in their visual perceptual abilities. These different perceptual abilities were associated with the ecological environments of the species, including the density of vegetation in which the animals lived.
The researchers then measured how closely matched the vocal communication signals of these species were to the perceptual capabilities of the receivers in the same species and in close relatives. They found that species with similar hearing abilities generally evolve more similar vocal communication signals, providing support for signal-receiver coevolution in vocal communication.
Dr. Tom Smulders, a lead author of the study based in Queen Mary's School of Biological and Chemical Sciences, said: "This research reveals a new dimension to our understanding of how animals evolve to communicate with one another. For the first time, we can see how signals evolve over evolutionary time in response to the perceptual capacities of their receivers."
"The next stage of this research is to understand the mechanisms by which animals evolve these perceptual biases. We could do this using neuroscience techniques to investigate the underlying neural circuitry in the brains of the animals," Smulders added.
