Language evolution: examining the link between cross-modality and aggression through the lens of disorders

Abstract

We demonstrate how two linguistic phenomena, figurative language (implicating cross-modality) and derogatory language (implicating aggression), both demand a precise degree of (dis)inhibition in the same cortico-subcortical brain circuits, in particular cortico-striatal networks, whose connectivity has been significantly enhanced in recent evolution. We examine four cognitive disorders/conditions that exhibit abnormal patterns of (dis)inhibition in these networks: schizophrenia (SZ), autism spectrum disorder (ASD), synaesthesia and Tourette's syndrome (TS), with the goal of understanding why the two phenomena altered reactive aggression and altered cross-modality cluster together in these disorders. Our proposal is that enhanced cross-modality (necessary to support language, in particular metaphoricity) was a result, partly a side-effect, of self-domestication (SD). SD targeted the taming of reactive aggression, but reactive impulses are controlled by the same cortico-subcortical networks that are implicated in cross-modality. We further add that this biological process of SD did not act alone, but was engaged in an intense feedback loop with the cultural emergence of early forms of language/grammar, whose high degree of raw metaphoricity and verbal aggression also contributed to increased brain connectivity and cortical control. Consequently, in conjunction with linguistic expressions serving as approximations/‘fossils’ of the earliest stages of language, these cognitive disorders/conditions serve as confident proxies of brain changes in language evolution, helping us reconstruct certain crucial aspects of early prehistoric languages and cognition, as well as shed new light on the nature of the disorders. This article is part of the theme issue ‘Reconstructing prehistoric languages’.

Reconstructing prehistoric languages

“…As for Gil's [10] contribution, drawing on a quantitative analysis involving the sample of 868 languages, he postulates a covariance relationship between grammatical complexity and certain aspects of cultural/socio-political complexity, inferring that earliest languages in prehistoric times had measurably simpler syntax, including simpler expressions of predication and tense-aspect marking. This consideration is consistent with the postulated proxies of proto-syntax in Benítez-Burraco & Progovac [8] (more below), who offer some concrete examples of compounds serving as proxies or ‘living fossils' of the earliest grammars. Likewise, according to the framework of Construction Grammar, adopted and discussed by Hartman & Pleyer [7] (more below), there is some continuity as well between the grammar and the lexicon from prehistoric times to present days.…”

“…While two other papers touch on the properties of earliest grammars and vocabularies (Hartman & Pleyer [7] and Benítez-Burraco & Progovac [8]), the contributions by Calude [9] and by Gil [10] focus most directly on these questions. Calude provides an overview of the research on number words, concluding that numerals 1–5 are the most stable across cultures, often being preserved for thousands of years, and that they are thus the ones that should be reconstructed for prehistoric languages, while higher numerals have emerged as an innovative tool in more recent times.…”

“…The contributions in this section focus on reconstructing prehistoric behaviour, cognition and/or the brain organization with the aim of inferring structural and functional aspects of prehistoric languages. Two contributions (Gil & Shen [11] and Benítez-Burraco & Progovac [8]) address the question of the concrete versus abstract nature of the first vocabularies and the role of metaphoricity/cross-modality in the shaping of the first grammars. Gil & Shen [11] consider a hypothesis that unidirectionality/asymmetry in the metaphorical domain evolves gradually, in several steps, with the first step correlating with the emergence of asymmetrical grammars universal to all humans (but not found in other species).…”

“…Furthermore, in an experimental setting, Gil & Shen [11] found that there is variability between speakers of two different languages in this respect, concluding that the development of unidirectionality in the metaphorical domain is a gradual, ongoing process. As for Benítez-Burraco & Progovac [8], they focus on the nature of selected proxies (fossils) of the earliest grammars, specifically those relevant to metaphoricity (cross-modality) and verbal aggression (insult), as found in living languages, including in disordered language. The authors purport to solve the puzzle of the link between aggression management, cross-modality and language complexity, and particularly, a persistent co-occurrence found in language disorders between heightened aggressive impulses and diminished metaphorical/figurative language.…”

Metaphors: the evolutionary journey from bidirectionality to unidirectionality

“…In accordance with general directionality, the mere presence of the grammatical medium activates the concrete/abstract conceptual hierarchy, yielding a preference for the more abstract Monday to be understood as explicated in terms of the more concrete Nile, appealing perhaps to the shared property of being long and slow-moving-under this interpretation, Nile is understood as the metaphorical source and Monday as its target. However, this preference comes up against the variegated grammatical constructions in (1) and (2), resulting in differential applications of particular directionality effects. In (1), the two terms occur in symmetric conjunctions, which, as shown by Fishman & Shen [13], are royalsocietypublishing.org/journal/rstb Phil.…”