What Differentiates Declarative and Procedural Memories: Reply to Cohen,Poldrack, and Eichenbaum (1997)

Cohen, Poldrack, and Eichenbaum (1997; hereafter CPE) offer an account of the nature of individual items in memory and how they relate to one another. They argue that there are two separate memory systems, procedural and declarative (Cohen & Eichenbaum, 1993; Cohen & Squire, 1980). These systems differ in their neuroanatomic substrates, in their operating characteristics, and in the nature of the representations they use. CPE argue that representations in the declarative memory system are compositional, meaning that declarative representations may be composed of other declarative representations. Declarative memories are also flexible, meaning they can be accessed in contexts that differ from those in which they were encoded. Procedural memories, on the other hand, are neither compositional nor flexible. I will argue that there is not sufficient reason to argue that procedural and declarative memories have these distinct characteristics. Both procedural and declarative memories are arguably compositional, and both can appear flexible or inflexible, depending on testing conditions.