Can we look at primate communication to learn more about human speech?

When you hear the word “communicate,” what do you think of? Do you think of people talking into cell phones? Do you think of a mother consoling a crying child? Often times, we don’t think that non-human animals communicate, but in fact, extensive research has been done to show that they do. Dogs bark, cats swipe their claws at people and animals, and birds chirp and sing. These are all forms of communication that animals use to interact with one another and other species. Research by Josef Rauschecker and Sophie Scott uncovered the ways that nonhuman primates’ ability to process speech communication may lead to better understanding of how humans process speech (Rauschecker & Scott, 2009). Rauschecker and Scott identified roles for different cortical areas in the perceptual processing of speech and analyzed how the primate auditory cortex works in functional processing.

For this research, Rauschecker and Scott analyzed 100 research articles to determine look at the neuronal mechanisms responsible for speech and language perception. These articles all suggest different or deeper understandings of how human and non-human primates process language and use speech. Even though non-human primates do not truly speak, they use other forms of verbal and nonverbal communication that are similar to the ways that humans communicate. This makes them excellent models for understanding more about the human auditory processing system. After analyzing the research, Rauschecker and Scott constructed potential models for the non-human primate auditory function which relates to human auditory function.

Previous research has suggested that there is a dual-stream process for auditory processing in primates and the ability for the dorsal pathway to contribute to spatial processing but not speech and language. Rauschecker and Scott’s research shows the dorsal pathway of the brain may be useful in auditory processing and language in the same ways that it is useful for spatial processing. Models of both spatial and auditory processing operate as “forward models,” which predict the consequences of actions. In speech and language processing, the research found that networks from the Broca’s area of the brain (primary for speech processing) and the primary motor cortex to the inferior parietal lobe (responsible for hearing) interact with signals from the auditory cortex. This informs the sensory systems that a motor signal is about to occur to articulate speech. If this is true in nonhuman primates, there is a high likelihood that it is true in humans due to the fact that humans are so similar to their primate relatives.

Source: Rauschecker, J. P., & Scott, S. K. (2009). Maps and streams in the auditory cortex: nonhuman primates illuminate human speech processing. Nature Neuroscience, 12(6), 718-724. doi:10.1038/nn.2331