Biolinguistics and the origins of human communication

Could learned sequences of actions have provided a foundation for language syntax?

According to research from Graziano (2006), there is a hierarchical organisational structure within the motor system that is based from various neuromotor features from ‘abstract motor intentions’ to ‘motor implementation parameters’ signalling in separable brain and spinal regions. This also gives rise to a ‘motor grammar’, through innate human behaviour, which Graziano argues is deeply embroiled in goal-oriented actions.

Through a multidisciplinary approach, Bernstein (1967) proposed a model to describe how such goal-directionality in behaviour could give rise to a ‘motor grammar’ using the evolutionary biomechanics of musculoskeletal actions. One concept was the ‘centrality of action goals’, where incorrect implementation of movement with regards to appropriate action is thought to provide a framework for learning, which in turn forms the basis for the theory behind hierarchical organisational of motor structures.

Within this, Bernstein also describes the action of motor retrieval, or motor recursivity. This is the idea that describes how learned motor components (that contain information on specific actions) can be recalled. This aspect of the model in particular has significant implications for communication, given that recursivity is shared among both language and motor action.

As stated by Chomsky (1957), recursivity is one notable feature of language which appears as a result of the ‘lack of an upper bound’ in grammatical sentences and length within universal language. However, this is where the similarities stop. While grammatical recursion relies on (as mentioned) nested structures, motor action can be noted as being formed of small sequential structures that repeat over a period of time.

Moreover, Fadiga et al (2006) argues that recursivity only exists in two forms within motor actions; in designing tools to build tools (high level processing) and in implementing the correct functioning of the Degrees of Freedom (DOF) in motor control states within specific cortical areas (low level processing). And as such, the process of concatenating motor elements to action in the goal-orientated structure works in tandem with language’s natural tendency to form structure and syntax. This theory is supported from research by Higuchi et al (2009), where neuroimaging (fMRI) data suggested a cross between tool usage and language in the Broca’s area. But most interesting of all, was that this was true in monkeys, and as such, it can be concluded that broca’s area involvement in tool use (and complicated hierarchical structures of modality within the motor system) can act as a model for primitive human cognitive function which predates language.

The role of the broca’s area has also been explored in Dausillio & Fadiga (2011)’s paper where the ventral premotor cortex (vPM) and posterior broca’s area (BA44) are documented to have aspects of similarity with the monkey’s homologous F5 area. Which Rizzolatti et al (1988) also supports, as the neurophysiological data indicated that F5 area within monkeys has shared commonalities with motor and mouth movements.

Moreover; Nishitani et al (2005) has also suggested that in terms of hemispheric asymmetry, great apes have a larger inferior frontal region (this corresponds to the human broca’s area) on the right side, and a smaller inferior frontal region on the left. This discrepancy (or asymmetry) suggests that vocalisation developed before speech from the neuroanatomical substrates of the left hemisphere around 5 million years ago. And that, the vocalisations emerged as a result of a gestural-system of communication for various reasons such as after-dark correspondence, hands-free discussions, and long-distance calls. But most of all, the cerebral asymmetry in the inferior frontal region of apes highlights lateral dominance for vocalisation as well as motor action.

Pasta and Aloimonos (2011) has shown from Chomsky’s minimalist programme (MP) model that motor action is structured in tool roles and affected-object tool role dictates the syntax of the motor action. Therefore, the effects of such then (as indicated by the study) manifests within human language, which leans towards the idea of learned sequences providing a foundation for language syntax, which is compounded by research through the neural overlapping of language parsing, use of tools, and gestural communication (Steele et al., 2011; Higuchi et al., 2009). However the problem of presenting empirical evidence for the biological basis (as opposed to computational) for the use of tools persists. Therefore, there as yet to be a study that investigate this in regards to the organisation of action.

Nevertheless, Nishitani et al (2005) offers a solution that motor sequences are the basis for syntax formation since they may evoke memories that are mapped to the observer’s ‘motor grammar’, or ‘motor vocabulary’. Especially since the Broca’s area plays a key role in holding sequential information via sensory aspects, and manual action via motor aspects. This can be determined via brain injury studies, where the left hemispheric impairment can significantly affect verbal sequencing and right hemispheric damage can non-verbal sequencing (Kim et al 1980). The cerebral lateralisation in verbal vs non-verbal sequential processing is particularly critical in describing asymmetry of inferior frontal region in great apes, and the implications for early human lingual processing.