LAUSR

ABSTRACT Despite evidence of a relationship between Apolipoprotein E (APOE) &egr;4+ and later‐life cognitive decline, the lifespan effects of carrying an &egr;4+ allele on cognitive ageing are not well understood. Evidence of &egr;4+ advantages in early‐life are inconsistent, but not inconsiderable. We explored the proposal that APOE &egr;4+ cognitive advantages arise only in response to complex and sensitive tasks targeting specific executive functions. We systematically manipulated executive demand within verbal fluency, decision‐making, prospective memory, and sustained attention tasks. Participants aged 18–25 years (21 &egr;4+, 63 &egr;33) also completed a measure of subjective effort. Under low executive demand, &egr;4+ made fewer verbal fluency word repeats compared to &egr;33 carriers. Under high executive demand, &egr;4+ showed lower costs associated with performing concurrent tasks, greater switching errors, and more verbal fluency root repetition errors. Overall, &egr;4+ appeared to be showing working memory updating advantages under conditions of low executive demand, more effective resource allocation under elevated levels of executive demand, and errors indicating different strategy use compared to &egr;33 carriers, including speed‐accuracy trade‐offs.