As a result, he developed a deep respect for his father.[224] In contrast, Adams had a rocky relationship with his mother, due to her high expectations of him, and her fear that her children would follow in the footsteps of her brother, who died of alcoholism.[224] His biographer, Nagel, concludes that his mother's disapproval of Louisa Johnson motivated him to marry Johnson in 1797, despite Adams's reservations that Johnson, like his mother, had a forceful personality.[224]
Though Adams wore a powdered wig in his youth, he abandoned this fashion while serving as the U.S. Minister to Russia (1809-1814)[225] and became the first president to adopt a short haircut instead of long hair tied in a queue and to regularly wear long trousers instead of knee breeches according to the fashion of the 19th century.[226][227] It has been suggested that John Quincy Adams had the highest I.Q. of any U.S. president.[228][229] Dean Simonton, a professor of psychology at UC Davis, estimated his I.Q. score at 165.[230] He reportedly spoke eight foreign languages (Dutch, French, German, Greek, Italian, Latin, Russian, and Spanish), more than any other U.S. president. 