If I may, dzug has hit the answer pretty squarely. Of the three modes of motion inherent in any aircraft, the yawing motion, the movement around the vertical axis can cause the most discomfort. As turbulence occurs, all aircraft, large and small, have a tendency for the nose to move to the left and right (and hence, the tail). All large, transport category aircraft are equipped with electronic sensing equipment called yaw dampeners which do a pretty good, but not totally thorough job of eliminating this discomforting motion. Most passengers can deal with the bumps and jolts that produce up and down movements, but the side to side movement can produce airsickness more easily. This is most pronounced the farther one is away from the center of motion, which is usually over the wing area...