Moderation-Mediation Effects in Bilingualism and Cognitive Reserve

Abstract

We first provide a critical review of the existing findings on bilingualism as a contributor to cognitive reserve from moderator-mediator warranting cause-effect research conclusions. We next address the question of direct or indirect effects between bilingualism and neurocognitive protective factors influencing the associated age-related mental deficits. The existing findings support bilingualism as a predictor and as a moderator. Third, we propose cognitive reserve models of bilingualism describing analytical approaches that allow testing of these models and hypotheses related to path strength and causal relationships between predictors, moderators, and mediators. Lastly and most importantly, we suggest using large datasets available via open repositories. This can aid in the testing of theoretical models, clarifying the roles of moderators and mediators, and assessing the research viability of multi-causal paths that can influence cognitive reserve. Creating collaborative datasets to test these models would greatly advance our field and identify critical variables in the study of the bilingual aging brain.

Keywords: bilingual cognitive reserve; bilingual mediators; bilingual moderators; cognitive reserve; mediating effects; moderating effects.

Figure 1

Bilingualism as a moderator interacting with predictor age moderating Alzheimer’s Disease (AD) markers (see Gollan et al., 2011).

Figure 2

Bilingualism (X) as a predictor variable, and Increased Gray Matter Volume (GMV) (M) mediating Delayed Onset of AD in bilinguals.

Figure 3

A hypothetical mediation (bilingualism) and moderation (immigration, education, immigration × education; immigration × bilingualism × education, immigration × bilingualism, and bilingualism × education) model of bilingual cognitive reserve (cf. Fairchild and MacKinnon, 2009); working memory capacity (attention span), and general intelligence (cf. Martin et al., 2020).