This experiment was designed to test the hypothesis that Tryon's strains of maze-bright and maze-dull rats are different psychological "types" of rats, and to identify specific behavior tendencies within each strain's maze-learning performance. 30 measures were obtained of learning, emotionality, activity, and other behaviors for samples of 10 Brights, 10 Dulls, and 15 rats of a median strain. The mean correlation of Brights with Dulls (an "inverted" correlational analysis) was -.19, whereas members within each strain showed high and positive correlations with one another (+.59, +.53). These results are interpreted as strongly confirming the type hypothesis. A study of the behavior profiles indicated that Brights are food-driven, economical of distance, low in motivation to escape from water, and timid in response to open spaces; while Dulls are relatively disinterested in food, average or better in water motivation, and timid of mechanical apparatus features. The conclusion was drawn that brightness and dullness in the original Tryon Maze may be accounted for in large part by such motivational and emotional patterns. Certain basic "cognitive" tendencies may also be different in the two strains. 24-item bibliography. (PsycINFO Database Record (c) 2016 APA, all rights reserved)