Neuroemergentism: At the intersection of ontogeny and phylogeny

Abstract

When considering how particular features of an organism develop, it is often intuitive to turn to examples of phylogenetic adaptation, or evolutionary change over time. The rapid darkening of peppered moths of industrial-era London provide a compelling case, as light-colored moths became easier for predators to spot in a city increasingly blackened by soot (Cook, 2003). Similarly, it is intuitive that the human brain evolved to allow for functions that would have benefited the survival of our ancestors, such as the ability to see and coordinate movement. What is perhaps less obvious, is how the brain carries out functions that are too new to have been selected for during human evolution, such as precise mathematics and language. In their article “Neuroemergentism: A framework for studying cognition and the brain,” Hernandez et al. (in press) review evidence showing that cognitive functions and their underlying neural bases can be best understood by considering both phylogenetic evolution of the brain, as well as ontogenetic development over an individual s lifespan to account for the impact of experience. The authors consider the theories of Neuronal Recycling, Neural Reuse, and Language as Shaped by the Brain, and explain that skills such as reading and numerical processing are made possible by recruiting existing, older neural structures for new functions. They further argue that a comprehensive theory should include consideration of developmental changes over time, and introduce Neuroemergentism as a potential unifying account that seeks to explain how pre-existing elements shaped through evolution are repurposed to meet an organism s developmental needs. In its conception, Neuroemergentism aims to provide a framework for the study of cognition and the brain. Going forward, the theory would benefit from greater specificity in order to transition from an explanatory account to a framework that generates testable and falsifiable predictions. As a first step towards this goal, we discuss three potential topics for which a Neuroemergentist prism could provide constructive insights: Bilingualism, language acquisition, and language attrition. We consider these three areas in light of data that are already compatible with Neuroemergentism and that could be developed further within its framework. For bilingualism, there is already substantial evidence that the effects of using multiple languages vary across the lifespan (Bialystok, Martin, & Viswanathan, 2005). For example, differences in executive function between monolinguals and bilinguals have been well documented among young children (e.g., Bialystok, 2001) and older adults (e.g., Bialystok, Craik, & Luk, 2008), but the effects become more tenuous among younger adults (e.g., Salvatierra & Rosselli, 2011). Bialystok et al. (2005) trace this development and propose that effects of bilingualism are less prominent among young adults because they are operating at peak efficiency, leaving little room for variability. Taking a Neuroemergentist approach could complement this work by systematically considering the neurological bases and changes associated with the behavioral data. For instance, increased white matter among bilinguals has been documented for both young children (Mohades et al., 2012) and older adults (Luk, Bialystok, Craik, & Grady, 2011), suggesting that enhanced cognitive abilities may result from better and more distributed connectivity (see Mount & Monje, 2017 for a discussion of experience-dependent myelination). Grey matter density has also been shown to increase with bilingual experience, and is correlated with both age of acquisition and language proficiency (Mechelli et al., 2004). Methodical examinations of change across