2.1. Participants

Sixty-six individuals participated in this study. They were invited according to their APOE allelic variants, through the NIHR BioResource (for APOE genotyping methods please refer to the NIHR BioResource website: https://bioresource.nihr.ac.uk/). For the present study, participants with APOE ε3/ε3, ε3/ε4, and ε4/ε4 genotypes were invited to participate, 22 (11 males and 11 females) per group (see Table 1 for demographics). Neither the experimenter nor the participants were aware of the genetic status at the time of testing (double-blind protocol).

Demographic characteristics of the final sample (11 male and females per group)

Key: ACE, Addenbrooke's Cognitive Examination.

All participants had normal or corrected-to-normal visual acuity and normal color vision. The study was approved by University of Oxford Ethics Committee. The Addenbrooke's Cognitive Examination III (ACE-III) test was administered as a general cognitive screening test to all participants (means scores in Table 1). None of the participants exhibited significant cognitive impairment using a cutoff of 88/100.