Testing of the functional capabilities of the vertical semicircular canals of the vestibular system is important in the diagnosis of patients with dizziness and imbalance. A new technology, termed the vestibular head impulse test (vHIT), is being developed for clinical use. A critical factor in this development is to measure the 3-dimensional motions of the head during these tests. The purpose of this study is to develop a method to accurately measures head movements during these tests and combine these data with eye movements that occur.