The Effect of Instructions upon Post-Rotational Sensations and Nystagmus

Abstract

By the technique of sensation cupulometry two matched groups, each of 7 subjects, were obtained. In a subsequent test one group received “strong” instructions and the other, which served as a control, weak instructions similar to those employed in the initial test. With the “strong” instructions there was a prolongation (p = 0.001) of the reported after-sensation, and a fall (p = 0.02) in threshold of the sensation cupulogram but no change in “slope”. In the control group there was no significant change of “slope” or “threshold”. The decay of post-rotational nystagmus was prolonged in the “strong” instruction group and reduced in the control group. It was inferred that the increase in the duration of the after-sensation was produced by a change in the afferent signal rather than by an alteration of sensory threshold.