To the Editor.
—There is widespread agreement that measurement of hypnotic responsivity has been a seminal contribution to the field of hypnosis. It has enabled disciplined scientific investigation to relate the trait of hypnotizability to a variety of other measures of personality, psychopathology, treatment outcome, and neurophysiologic phenomena. Dr Hilgard, whose article (see p 963) is critical of one aspect of our work, has made major contributions to the development of the field. Inevitably, there will be disagreements about measurement instruments, and it is unlikely that any one instrument will be the best measuring device in all situations. It is within this context that we examined Hilgard's critique of the hypothesis that the eye-roll sign (ER) is lawfully related to measured hypnotic responsivity on both theoretical and statistical grounds.Hilgard stated that the apparent relationship between the ER and hypnotizability is illusory. The crux of this allegation is that we