Bimodality, dimensionality, and the notion of hypnotic types.

The notion of hypnotic types--of qualitative differences in the mechanisms by which people respond to hypnotic suggestions--is examined with respect to the kind of evidence that has traditionally been seen to support it. Bimodality in the distribution of hypnosis scores has been taken as evidence for two "types" of hypnotizability. It is argued that little can be said about the nature of underlying processes from the distribution of raw scores. The relationship of factor analytic results to possible underlying typologies is examined. It is concluded that the present evidence simply does not allow an evaluation of the merits of current typological formulations.