The effect of different psychophysical methods on visual orientation during tilt

The visual vertical with 30 deg right head tilt was determined by three psychophysical procedures: the methods of adjustment with and without bracketing and a modified up-and-down (staircase) method. The visual vertical was on the opposite side of the gravitational vertical to tilt (E-effect) under all conditions. However, the E-effect measured by the up-and-down method was significantly larger than the combined average of the two methods of adjustment. The methods of adjustment with and without bracketing yielded approximately the same means for the visual vertical when averaged over starting positions, but differed significantly in the linear trends taken over starting positions. A greater error of anticipation resulted when bracketing was not allowed.