This chapter concerns the dimensionality inherent to describe and understand schizotypy and schizotypal personality disorder (SPD). It concerns attempts that are being made to discover experimental paradigms to characterize the cognitive functioning of schizotypal and schizotypally disordered individuals; or, develop markers of cognitive nature that might be helpful in high-risk and genetics research. Two traditional views of dimensionality can be discerned, and roughly align to the psychiatric and psychological models. The psychiatric view of continuity is characteristically quasi-dimensional. Focusing on variations within the illness domain, and taking the abnormal state as its reference point, it construes dimensionality as degrees of expression of a disease process. Typical questions include diagnostic and nosological issues such as the relationship between full-blown psychosis and forms of personality disorder as possible formes frustes of disease: SPD in the case of schizophrenia. The fully dimensional takes normality or health as the starting point.