Developmental instability in schizotypy and psychosis

A brilliant thinker and a gifted teacher, Paul Meehl's love for and dedication to the philosophy of science did not lead him, as it seems to have led others, to assume that all minds have the same structure and differ only parametrically. One of Meehl's main interests in the latter part of his career was in taxometric methods for identifying psychological types or taxa. Another taxonomic method seeks traits that are very similar, for genetic reasons, in monozygotic twins, but not in other sib pairs. These emergenic traits may be more common than previously realized. Two examples are briefly discussed.