How intelligence mediates liberalism and prosociality

Individuals of most or least intelligence consistently orient further left politically than those of middle intelligence, producing a U-shaped curve. Evidence advanced to support alternative intelligence-moderation and political typing hypotheses is explained mainly in terms of that U-shaped curve. The lower intelligence extreme orients toward the left because it is populated disproportionately by leftist beneficiaries (e.g., economic and racial minorities). The leftist vote by leftist beneficiaries strictly on issues on which they are leftist beneficiaries is attributed to personal experience, rather than self-interest. While self-interest alone is a weak influence, personal experience with a segment is a liberalizing factor on issues involving that segment because it increases the likelihood of oneʹs attributing the stations of individuals in that segment to external causes and of oneʹs being empathetic and trusting toward that segmentʹs individuals. Intelligence confers leftist tendencies primarily for the same reasons, which explains the leftism of the higher intelligence extreme. Unlike the lower intelligence extreme, the higher intelligence extreme is broadly leftist, self-identifies as liberal, and is strongly prosocial overall. An explanatory costly signaling hypothesis is superfluous.