Abstract.—Lower bound reliabilities for the various parameters of two previously suggested models for the serial colour word test—one linear and one quadratic —are derived and estimated. The quadratic model gave mostly very low reliabilities, and the stronger, linear model also gave only a few high reliabilities. Validity was studied by means of discriminant functions (4 groups being used; 3 clinical and 1 normal). The validity of the test was low. The linear model gave the best results under cross valid