The Collaborative International Dictionary of English v.0.48:

Associationism \As*so`ci*a"tion*ism\, n. (Philos.)
   The doctrine or theory held by associationists.
   [1913 Webster]

WordNet (r) 3.0 (2006):

associationism
    n 1: (psychology) a theory that association is the basic
         principle of mental activity [syn: associationism,
         association theory]