Figure 4.

Audiovisual reference frame problem. When an audiovisual target is straight ahead (center panel), the auditory and visual reference frames coincide; that is, a plane orthogonal to the auditory head-centered reference frame (blue field) is parallel to the plane orthogonal to the visual eye-centered reference frame (red field), and both are perpendicular to the audiovisual information source (speaker). When the target is moved eccentrically (upper panels), the head-centered and eye-centered reference frames are no longer parallel, with the eye-centered reference frame having rotated around a vertical axis (for horizontal eye movements). In this example, the eye-centered reference frame is still perpendicular to the audiovisual target but the head-centered reference frame is not.