Assessment procedures that can significantly enhance motivation to perform are needed so that poor performance due to low or avoidance motivation is not misdiagnosed as indicating ability deficits or as symptomatic of learning disabilities (LD). In this connection, research is under way to investigate the degree to which a highly motivating computer game learning task can improve differential diagnoses of LD. Findings from the initial investigation indicate that a large proportion of students diagnosed as LD were able to learn effectively when pursuing such a task. The results illustrate the key role motivation plays in determining the validity of diagnostic assessment and demonstrate the potential value of similar tasks for use in differentiating, from among individuals diagnosed as LD, those who do not have impaired learning processes.