Abstract
Pupillary changes were measured in response to audio instructions while a subject looked at a visual pattern. Results shows that audio instructions cause the pupil to delate and that pupillary changes are directly related to mental activity. The same results are found when audio instructions are given without presentation of visual patterns. Pupillary changes which occur when a pattern is looked at fixedly are discussed, and subjects can be categorised by their types of pupillary changes. It is suggested that the pupillary response is an indicator, of mental activity.
