The ability of humans to adapt their behavior so as to survive and succeed in their environment is a most fundamental and valuable characteristic of the species. The development of computers and the associated concept of programming has led to the natural metaphor of describing adaptive behavior as program modification and development (Lilly, 1969, Keele, 1973). This paper describes a model of the human cognitive system consisting of production systems and a distributed memory. Production systems are the mental programs which act upon the states of available memories. Within this framework, a means for the adaptation of production systems by production systems is defined.