Welcome to the third edition of My Favourite Parts From. This time we’re looking at my highlights from Robert Plomin’s bestselling Blueprint: How DNA makes us who we are. A. the most important environmental factors, such as our families and schools, account for less than 5 per cent of the differences between us in our mental health or how well we did at school – once we control for the impact of genetics. Genetics accounts for 50 per cent of psychological differences, not just for mental health and school achievement, but for all psychological traits, from personality to mental abilities. I am not aware of a single psychological trait that shows no genetic influence.