What Distinguishes Us as Human?

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It’s commonly agreed that what sets us apart from other animals is our linguistic ability. However, musical ability is also unique to humans. Common to both language and music is the capacity to unconsciously combine conceptual elements in an infinite number of ways.

Toolmaking and cognitive evolution

Chipping a piece of flint to make a hand axe seems easy enough. If, 1.76 million years ago, austrolipithicenes could do it, then surely now anyone could. But although early stone tools were simple, their craft became increasingly complex and it took a considerable amount of skill to make them.

As discovered by Dietrich Stout, learning to make a stone hand-axe can take up to 300 hours – a practice called ‘knapping.’ It requires multiple stages of planning, several tools, fine motor coordination and inhibitory control. Monitoring of the knapping learning curve using multiple brain imaging techniques shows that acquiring advanced knapping skills produces changes in the brain implicated in greater cognitive control. Crucially, these studies imply that over evolutionary time, our brains changed in a manner to fit the commendable skills required for making complex stone tools. It is now well recognized that the evolution of the motor system in primates underlies great advancement in cognitive capacity.

What happens in the brain while an advanced knapper knaps? Imaging studies reveal activity in Broca’s area – part of the inferior frontal gyrus (IFG). Related primate studies have shown that within area F5, which is considered the ‘monkey Broca’s area’, are the mysterious mirror neurons that are active during both the observation and execution of goal-directed hand movements. Theories regarding the function of mirror neurons are numerous and far-reaching. One of the most plausible claims, however, is that they facilitate learning through imitation. However, the fine motor coordination required for making advanced stone tools are thought to be too complex to be routinely learned solely by ‘hominin see – hominin do’. Instead, this ability required complex representations of sequences of goal-oriented motoric action – a notion first implied by archaeologist Andrė Leroi-Gourhan in 1964. To some, this sequencing has been termed a ‘grammar of action.’ This representational aspect facilitates a critical cognitive leap, beyond simple mimicry.

Studies of the IFG clearly show a surprisingly vast functional overlap in linguistic and praxis (detailed motor planning and execution). To quote Stout:

“… it is now recognized that frontal ‘language relevant’ cortex extends across the entire inferior frontal gyrus (IFG) and contributes to a diverse range of linguistic functions… Furthermore, IFG is known to participate in a range of non-linguistic behaviours from object manipulation to sequence prediction… It has been proposed that this superficial behavioural diversity stems from an underlying computational role of IFG in the supramodal processing of hierarchically structured information.”

The ability to process hierarchically structured information is key here. It could have been crucial for stone tool making, language and ultimately for survival. It also underlies another uniquely human ability – musicality.

Language and music

Charles Darwin thought that musical enjoyment was something common to many species: “The perception, if not the enjoyment, of musical cadences [i.e., melodies] and of rhythm is probably common to all animals, and no doubt depends on the common physiological nature of their nervous systems.” But is this correct? Do other animals engage in and react to music in the same way we do?

The focus of music is often on this emotional quality. Indeed, music moves us in more than just physical ways and provokes intense reactions. Where does the emotional charge of music come from? Musical enjoyment is tied to the release of dopamine. Similarly, dopamine release underlies addictive behaviours – the intense feelings of anticipation and reward that can happen when playing a slot machine and winning, for example. Music we like often contains climactic points that we unconsciously predict because we have previously identified these musical patterns. When our predictions about these climactic points turn out to be correct we find it satisfying in the same physiological manner.

Considering our faculty for such pattern identification from a broader perspective, unconsciously identifying patterns in sound is a feat common to both musical and linguistic abilities. Specifically, both music and language are organized syntactically – they are arranged to according to a complex, rule-based pattern that we amazingly learn and practice unconsciously. Syntax is the faculty that enables us to combine discrete structural elements into larger sequences, using a shared rule-based system. When music and language don’t follow these rules they become noisy or nonsensical. In fact, studies involving a number of brain imaging and neural activity recording techniques consistently show similar responses (some indistinguishable) to syntactic violations in both music and language.

The shared functional and anatomic resources of linguistic and musical processing are, in fact, central to explanations of generalized improved learning in students with musical training. Musical training and aptitude has in fact, been commonly used as a significant predictor of academic success. Linguistic and musical activities are thought of as tools for increasing prefrontal cortex development and thus promote increases in cognitive capacity.

A broader sense of us

Saying that humans are defined by exceptional musical and linguistic capability is a rather clumsy and narrow way to state our uniqueness. Importantly, what underlies both these abilities is the capacity to structure conceptual elements into an infinite number of complex arrangements. Thus, as best as I can put it, what sets us apart from other animals is our infinitely generative syntactic capacity. Applied solely to linguistics, this feat has been proposed as something called ‘Merge.’ Perhaps a broader term that encompasses music, awaits us.

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