Neural Correlates of Syntax and Proto-Syntax: Evolutionary Dimension

Abstract

The present fMRI study tested predictions of the evolution-of-syntax framework which analyzes certain structures as remnants (“fossils”) of a non-hierarchical (non-recursive) proto-syntactic stage in the evolution of language (Progovac, 2015, 2016). We hypothesized that processing of these structures, in comparison to more modern hierarchical structures, will show less activation in the brain regions that are part of the syntactic network, including Broca’s area (BA 44 and 45) and the basal ganglia, i.e., the network bolstered in the line of descent of humans through genetic mutations that contributed to present-day dense neuronal connectivity among these regions. Fourteen healthy native English-speaking adults viewed written stimuli consisting of: (1) full sentences (FullS; e.g., The case is closed); (2) Small Clauses (SC; e.g., Case closed); (3) Complex hierarchical compounds (e.g., joy-killer); and (4) Simple flat compounds (e.g., kill-joy). SC (compared to FullS) resulted in reduced activation in the left BA 44 and right basal ganglia. Simple (relative to complex) compounds resulted in increased activation in the inferior temporal gyrus and the fusiform gyrus (BA 37/19), areas implicated in visual and semantic processing. We discuss our findings in the context of current theories regarding the co-evolution of language and the brain.

Natural/sexual selection: What’s language (evolution) got to do with it?

“…While we did not find a contrasting effect in Broca's area, we found that transitives, contrasted with middles, evoked greater activation in the precentral gyrus (BA 6), proposed to be part of the "Broca's complex" (Ardila et al 2016). In a related fMRI experiment (Progovac et al 2018b), we tested the processing of English full sentences with TPs (e.g. The case is closed; The apology is accepted), contrasted with TP-less small clauses (Case closed; Apology accepted), and found a significant difference in both Broca's left BA 44 and right basal ganglia for full (TP) sentences vs. (TPless) small clauses, affirming the relevance of Broca's-basal ganglia network for the processing of more articulated, layered syntax.…”

“…kill-joy; pick-pocket; cry-baby) vs. hierarchical compounds (e.g. joy-kill-er; boot-licker; whistle-blow-er) and found a robust effect in the fusiform gyrus area (BA 37) (Progovac et al 2018b), the area where visual processing and certain non-compositional semantic processing (e.g. concreteness, metaphor) come together (e.g.…”

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

“…In truth, vivid compounds and ideophones may share other features of interest, including possibly a common neurobiological substrate. As shown by Progovac and colleagues [50]), two-slot compounds (the kill-joy type), in contrast with the more complex - er counterparts (i.e. joy-kill-er type), recruit the fusiform gyrus area (specifically BA37), the visual area that is also implicated in synaesthesia, a condition entailing abnormally enhanced cross-modal activity (more on this in the next section).…”

“…A second interesting feature of these compounds is their raw, visceral effect (e.g. [45,50]), and particularly, their great propensity for verbal aggression. In many cultures, comparable compositions are used in verbal duels/contests, whose purpose seems to be to replace physical fighting, thus contributing to a better survival of those who engage in verbal, as opposed to physical, duels (for more discussion, see e.g.…”

Minimalism in the Light of Biology: What to Retain and What to Discard?

“…While in some cases one may be justified in positing a null category, this blanket declaration of uniformity takes away the tools necessary for deciding when this is justified, and when not, giving rise to a host of unfalsifiable claims. Such sweeping claims are also harmful for biological considerations, because it is exactly the variability, the contrasts and comparisons among different constructions, that reveal the evolutionary primitives of syntax (e.g., Progovac, 2015, 2016), which can also be used to probe language variation and language representation in the brain (e.g., Progovac et al, 2018a,b).…”