Birth Cohort Differences in the Monitoring the Future Dataset and Elsewhere: Further Evidence for Generation Me—Commentary on Trzesniewski & Donnellan (2010)

A substantial majority of published studies have reported increases of individualism and materialism and declines in mental health and interpersonal trust over generations. The data Trzesniewski and Donnellan (2010, this issue) present from the Monitoring the Future (MTF) survey of high-school students is almost entirely consistent with these previous findings, showing decreases in civic interest and trust and increases in high expectations, materialism, and self-satisfaction. Problems with measurement and variable labeling explain the few seeming discrepancies. They analyze only 15% of the variables in MTF, ignoring many others that also demonstrate increases in individualistic traits. Ecological correlations are not an issue in previous studies as the individual-level standard deviation is used to compute effect sizes. Increases in narcissism are clear when important moderator variables (e.g., campus) are controlled. The real puzzle is why these authors’ conclusions fall so far from the data.