An experiment to determine, for achieving correct solutions to the Hatrack Problem whether prior experience on a simpler version of the problem helps and the effects of positive and negative reinforcement. After 30 min., 50.0% of the 30 Ss with no experience but only 25.0% of the 60 Ss with experience on the simpler version solved the problem ( p < .05). Positive and negative reinforcement showed no differential effects for 30 Ss receiving each. Previous experience may inhibit productive problem solving by providing too many false directions. Principles of reinforcement developed for learning are limited in their applicability to problem-solving behavior.