The correspondence is composed of:-
E97.57 - a collection of letters (11), typescript and manuscript, and some notes on calculations, relating to investigations into Aitken's abilities as a mental calculator, dating from 6 December 1960 to 7 December 1961, from Aitken (on either paper headed with Mathematical Institute, Chambers Street, Edinburgh; or, private address on Primrosebank Road, Edinburgh) to Hunter (Department of Psychology).
E97.58 - a collection of letters (6), typescript, also relating to investigations into Aitken's abilities as a mental calculator, dating from 12 December 1960 to 22 January 1962, with one letter having the paper ' Characteristics of decimalizing performance'; and, letters (22) from various people to Hunter dating from 4 May 1961 to 7 June 1978 including letters from Sir Frederic C. Bartlett (1884-1969) written between 4 May 1961 and 24 June 1962, and letters between Hunter and Dr. John D. Sutherland (1905-1991) written between 15 January 1962 and 23 July 1977.