He was born in Christiania as a son of educator Jacob Jonathan Aars (1837–1908) and his wife Anna Ernesta Birch-Reichenwald (1838–1919).
[3] Aars finished his secondary education in 1887, and graduated from the Royal Frederick University with the degree cand.theol.
He studied abroad from 1894, and was a research assistant under Götz Martius and Angelo Mosso.
degree in 1897 with the thesis Die Autonomie der Moral, and in the next year he was elected as a member of the Norwegian Academy of Science and Letters.
He requested the establishment of a Department of Psychology at the Royal Frederick University,[1] but it took more than ten years before this wish materialized.