FIGURE 3.

Hemoglobin concentrations are associated with cognitive performance. (A) Blood hemoglobin concentrations were positively associated with overall accuracy across the cognitive battery. Solid line represents the model fit for hemoglobin covarying for age and sex. Shaded portion reflects the CI of the fit. Density plots depict the distributions of the plotted variables. (B) Hemoglobin significantly mediated the effect of participant sex on overall accuracy, and the strength of the mediation effect was dependent on age (a moderated mediation effect). The moderated mediation effect was such that hemoglobin significantly mediated the association between overall accuracy and participant sex during adolescence—when sex differences in hemoglobin emerge—but not during childhood. ∗P = 0.020, n.s. not significant (P = 0.508).