FIGURE 2.

Relationships between age, loss aversion, and cortical thickness. (A,B) Loss aversion (λ) follows a quadratic trajectory with age, whereas cortical thickness of the posterior cingulate cortex (PCC) declines linearly with time. Shading indicates standard error confidence intervals. (C) Cortical thickness of the PCC mediates age-related changes in λ. The effect of age on PCC thickness is given by “a.” The effect of PCC thickness on λ is given by “b.” The Average Direct Effect (ADE; “c”) is the effect of age on λ when controlling for the mediator of PCC thickness. To calculate the Total Effect (c) of age on λ, without accounting for the mediator, both age and age² were included in the model and the regression coefficient for age² was taken as the strength of the effect. The causal mediation analysis was performed using nonparametric bootstrap confidence intervals and Monte Carlo simulations. The model included age, age², race/ethnicity, scanner, and estimated intracranial volume, as well as PCC thickness as the mediator. Age² was specified as the variable of interest. The measure of significance was given by the Average Causal Mediation Effect (ACME; p = 0.018*). Asterisks denote statistically significant results. *p < 0.05, **p < 0.01. (D) A negative relationship between PCC thickness and λ exists in older participants, but no relationship is present in participants under 35 years. The age of 35 was used to split the data into younger and older groups as it approximates the inflection point of the age-λ quadratic.