The neurostructural and genetic basis of human values

This thesis is aimed at investigating the neurobiology underlying individual variation in human value orientation. In over 80 nations, human values have been investigated under the framework of the circumplex model of human values (Schwarz, 1992). The present research probes specific biological markers of the human values described in this model, including macrostructural and microstructural properties of the human brain, brain activation and genetic components. The first section of the thesis investigates human values in the context of behavioural genetics. The motivation of this research is to identify the genetic representation of human values. To this end, I utilized knowledge in personality genetics to investigate an association between values and a specific genetic component: the polygenic neuroticism score. The results indicated that the polygenic neuroticism score was associated with individual differences in human values in a sinusoidal manner that is consistent with Schwartz’s (1992) model of values. These results suggest that it is useful to consider human values in analyses of genetic contributions to personality traits. The second section of the thesis describes two studies aimed at identifying the neurostructural basis of values. Specifically, this first study aimed at identifying the neural substrates that account for individual variation in the values assessed within Schwartz’s model. This individual variation was reflected in both macrostructrual (volume) and microstructural (myelin volume fraction) properties of brain white matter. The second study focused on a specific type of human values: hedonism values. It aimed at identifying the neurostructural link between hedonism and reward-related processing. The results provided evidence of a “hedonic hub” in the human brain by delineating how an intricate network of structures is associated with hedonism. These findings establish the first neurostructural link between hedonism values and the classical neurobiological pathways of the reward circuitry. Building on the previous section, the last chapter investigates the effect of human values on reward-related processing in the context of economic decision making and self-interest. Participants made foraging decisions for themselves and for a charity of their choice in two different foraging paradigms. Across both foraging tasks, self-focused individuals, compared to social-focused individuals, obtained more rewards when foraging for themselves than when foraging for others. This evidence reveals a dynamic interplay between an evolutionarily entrenched decision making system and the higher order belief system of individuals. Taken together, these findings provide new information helping to delineate the biology of values. They also pave the way for a more detailed explanation of psychopathological syndromes such as neuroticism and anhedonia in major depression