A passenger seat includes a frame, a bottom, a back, and a headrest, and incorporates a cylindrical motion support member. The support member includes a stationary member carried by the passenger seat, including a concave surface having a cylindrical curvature. A moveable member has a convex surface with a cylindrical curvature disposed in contact with the concave surface, and a support surface for supporting at least a part of a passenger's body The moveable member is selectively positionable along the concave surface. In another variation, the seat back and/or seat bottom is moveable in a conical motion.