Shared Dopaminergic Mechanisms Behind Extraversion and Executive Functions: An Experimental Approach

Abstract

Initial studies suggest that extraversion and executive functions (EFs), such as working memory updating and shifting, are associated because they partly share individual differences in the dopamine (DA) system. However, it yet remains open whether (1) initial findings are replicable, especially regarding the sensitivity of extraversion-EF associations towards pharmacological manipulations of the DA system, (2) these associations are specific to updating or shifting, or can be attributed to rather general executive processes needed for all EF tasks, and whether (3) extraversion and EFs also causally affect each other. The current project approached these questions in three studies by investigating how performance in several EF tasks is affected by a manipulation of either DA activation via a pharmacological manipulation (DA receptor blocker sulpiride vs. placebo; studies 1 and 2), or extraverted states via acting instructions during a group discussion (enacted extraversion vs. introversion vs. control; study 3). Results of study 1 (N = 92) were in line with our expectations, as we found the interaction between drug condition and extraversion to explain performance in two EF tasks (updating, shifting), and that task performance could be partly explained by shared performance variance among tasks. Study 2 had a design similar to study 1 with several methodological improvements including a second task targeting shifting, but could not replicate any of the previously found effects in a larger sample (N = 200). In study 3 however (N = 108), we unexpectedly found extraversion-EF associations (updating, shifting), although we only expected effects for the three conditions of experimentally manipulated extraverted states. Although (state) extraversion did not seem to have a causal effect on EFs, it affected the spontaneous eye-blink rate as a putative marker of striatal DA activation. Overall, the results are compatible with a role of DA in extraversion-EF associations in studies 1 (sensitive to sulpiride) and 3 (change in eye-blink rate). As results of study 1 were not replicable in study 2, and we found no indication of (state) extraversion causally affecting EFs in study 3, the results are mixed at best. Considering limitations such as low EF task reliability, implications of the present results as well as future directions are discussed.