Cognitive system-principles, styles of perceiving, have been shown by previous research to operate as individual personality constants over a variety of waking conditions. Do they function similarly in dreams? The dimension of flexibility (openness to change, diversity in expression, tolerance for fantasy, and lability in emotion) and rigidity (tight defense against variation or change) were measured on the Rorschachs and in the dreams of patients in psychotherapy. To a significant degree the way a patient responded in this variable to one measure was correlated highly with the way he responded to the other. One inference is that more highly developed adult ego functions may have forerunners in the primitive ego formations seen in dreams.