The rod and frame effect and induced head tilt as a function of observation distance

Several experiments investigated the influence of a tilted luminous frame on the rod and frame effect (RFE) and on adjustments of the head to apparent vertical, while observation distance to the frame was varied between 1 and 5 m. Comparisons of repeated measures from the same subjects as well as between independent groups showed that distance was a highly effective variable. Both the RFE and the apparent head tilt varied inversely with distance to the frame, diminishing Lo zero at about 5 m. Since head settings were in the direction of the tilted frame, the latter may be inferred to have caused an induced head tilt (IHT) opposite in direction to the tilted frame, when the head was objectively upright. Issues discussed were the role of IHT in the RFE and factors underlying the role of distance in both phenomena.