Smith was described by several of his contemporaries and biographers as comically absent-minded, with peculiar habits of speech and gait, and a smile of "inexpressible benignity".[51] He was known to talk to himself,[45] a habit that began during his childhood when he would smile in rapt conversation with invisible companions.[52] He also had occasional spells of imaginary illness,[45] and he is reported to have had books and papers placed in tall stacks in his study.[52] According to one story, Smith took Charles Townshend on a tour of a tanning factory, and while discussing free trade, Smith walked into a huge tanning pit from which he needed help to escape.[53] He is also said to have put bread and butter into a teapot, drunk the concoction, and declared it to be the worst cup of tea he ever had. According to another account, Smith distractedly went out walking in his nightgown and ended up 15 miles (24 km) outside of town, before nearby church bells brought him back to reality.[52][53]

James Boswell who was a student of Smith's at Glasgow University, and later knew him at the Literary Club, says that Smith thought that speaking about his ideas in conversation might reduce the sale of his books, and so his conversation was unimpressive. According to Boswell, he once told Sir Joshua Reynolds that 'he made it a rule when in company never to talk of what he understood'.

He sounds like a moron.

a rule when in company never to talk of what he understood'.