Tool Use and the Emergence of Language
Interdisciplinary research shows the affinity of language and motor skills.
Posted Apr 24, 2016
Current research on the evolution of language shows that we need to move beyond classifying people as “visual” or “verbal.” Using language well involves a vast range of skills, from finely controlling the intonations of one’s voice to hearing other voices’ inflections, interpreting gestures, deciphering handwriting, and learning grammatical patterns. Would anyone call a deaf scholar who excels at sign language a “verbal” but not a “visual” person?
Two weeks ago, a group of researchers convened at Emory University to discuss connections between the evolution of language and the use of tools. I attended the conference, one in a series of ABLE (Action, Brain, Language, Evolution) workshops run by Michael Arbib of USC. This one, “From Tools and Gestures to the Language-Ready Brain,” was co-organized by three Emory scientists: Dietrich Stout, an expert on Paleolithic stone tools; Todd Preuss, an authority on brain evolution; and Erin Hecht, who conducts neuroimaging in monkeys and humans (Hecht et al. 2012). Stout teaches students to make stone tools and works with Hecht to study changes in brain connectivity during tool-making training. Stout’s work was featured in the March 2016 issue of Scientific American (Stout 2016).
The scientists involved in the “Language-Ready Brain” workshop study birds’ nest-building, monkeys’ nut-cracking, children’s and chimpanzees’ gestures, and adult humans’ action-planning. Together, these investigators combine the techniques of neurology, neuroscience, psychology, anthropology, and primatology with the perspectives of biological and cultural evolution. By comparing their findings and thinking across disciplinary lines, they are trying to learn how language evolved.
In the early 1990s, psychologist Merlin Donald presented evidence that a motor “breakthrough” in primates preceded the evolution of language (Donald 1993, 739). Evolution tends to build on existing structures, and probably, language evolved from capacities adapted for other purposes, such as planning and imitating action sequences and processing visual information. Cognitive neuroscientist Erin Hecht pointed out that tool and language use both involve complex integrations of visual and motor information. Someone watching a sculptor chisel stone will follow her movements and imagine herself making them; someone joining a conversation will watch people’s gestures and try to figure out what is going on. Within a single lifetime and in the longer course of evolution, tool use and language-learning may have relied on mirror activity. Finely tuned motor and language skills, both of which are learned, may depend on mirror neurons, motor neurons that are involved in producing actions and that fire when a person observes other people performing these actions. Motor and language skills may seem distinct, but in human brains they are closely related.
What is the evidence for an evolutionary affinity between motor development and language? Broca’s area (the left inferior frontal gyrus in the frontal lobe), known since 1861 to be involved in speech production, engages in many other activities. Giacomo Rizzolatti, whose group discovered mirror neurons in the early 1990s, views Broca’s area as a jumble where “phonology, semantics, hand actions, ingestive actions, and syntax are all intermixed” (Rizzolatti and Craighero 2004, 186). Linguist David Kemmerer reports that Broca’s area plays a role in “imitation,” music-making, and “visuo-spatial perception” (Kemmerer 2011, 6). Erin Hecht, who uses neuroimaging techniques, said that Broca’s area is activated by complex forms of tool use. Michael Arbib has proposed that the close relationship between Broca’s area and hand-related motor neurons in monkeys points to a role for gestures in the evolution of language (Arbib 2012). Psychologist Virginia Volterra has revealed how children learning speech incorporate their sounds into systems of gestures. Clinical, behavioral, and neuroimaging evidence shows how greatly language relies on systems that enable complex visual, spatial, and motor skills.
If one defines tool use as broadly as language, this family affinity makes sense. Neuroscientist Atsushi Iriki pointed out that all primates shape their environments and are in turn shaped by them. Psychologist Dorothy Fragaszy offered an intriguing definition of “tool,” applicable to species far beyond humans: A tool alters the boundary between a body and an environment by adding a new degree of freedom. An object is a tool if an individual handles the body plus the tool differently than she would the body alone. Iriki added that tools may extend and externalize the sensory as well as the motor apparatus. When one hears “tool,” one might picture a human hand holding a hammer, but crows use tools, too. Susan Healy, who studies animal cognition, described birds’ elaborate uses of materials to build nests, and their improvement with practice. The phrase “tool use” may narrow a broad, evolutionary category by imposing a concept familiar to humans. If we thought in terms of a general, creative ability to use environmental materials to enhance one’s life, “tool use” would be shared across many more species.
When the ABLE scientists split up into discussion groups, some new questions arose. By chance, I landed in a group containing four of the meeting’s nine female researchers. What would have been required for language to evolve, we asked? Human ancestors would need a highly developed vocal apparatus, a mirroring capacity, and abilities to simulate, imagine, and look into the future. They would also need social skills that would permit teaching, turn-taking, and joint attention. Most significantly, they would need something not yet mentioned at the conference: affect. Human ancestors would need emotion that would drive them to pay attention. They would have to want to talk. This group composed largely of female scientists agreed that affect should be incorporated into evolutionary models. “Why are we trying to cook up language out of the motor system?” asked one. Probably, language evolved from a combination of existing capacities provided by the motor, auditory, visual, and spatial processing systems. Today, human language continues to diversify and evolve by drawing on all the systems that have gone into its making.
The ABLE conference took place at Emory University on April 10-12, 2016, and was organized by scientists Michael A. Arbib, Erin Hecht, Todd Preuss, and Dietrich Stout. I am grateful to the organizers for inviting me to participate in the meeting.
Arbib, M. A. (2012). How the Brain Got Language: The Mirror System Hypothesis. New York; Oxford: Oxford University Press.
Donald, Merlin. 1993. “Précis of Origins of the Modern Mind: Three Stages in the Evolution of Culture and Cognition.” Behavioral and Brain Sciences 16 (1993): 737-91.
Hecht, E. E., Gutman, D. A., Preuss, T. M., Sanchez, M. M., Parr, L. A., & Rilling, J. K. (2012). "Process Versus Product in Social Learning: Comparative Diffusion Tensor Imaging of Neural Systems for Action Execution–Observation Matching in Macaques, Chimpanzees, and Humans." Cerebral Cortex. doi: 10.1093/cercor/bhs097.
Kemmerer, David. 2011. “The Cross-Linguistic Prevalence of SOV and SVO Word Orders Reflects the Sequential and Hierarchical Representation of Action in Broca’s Area.” Language and Linguistics Compass 1–17.
Rizzolatti, Giacomo, and Laila Craighero. 2004. “The Mirror-Neuron System.” Annual Review of Neuroscience 27: 169-92.
Stout, D. (2016). “Tales of a Stone Age Neuroscientist.” Scientific American 314 (March), 28–35, doi:10.1038/scientificamerican0416-28.