RESUMEN
To overcome certain disadvantages of the tilted-mirror situation as a technique for separating visual and postural determinants of the perceived upright, a new procedure was developed. The S was presented with a small tilted room, on the back wall of which was a rod which he had to adjust to the true upright. In a first test, judgments of the rod were obtained with body upright, and under three different conditions of the field: (a) The S, standing at a distance from the tilted scene, viewed it through a tube which restricted his view to the interior of the scene. (b) The S stood directly in front of the scene without a tube. (c) The S stood at a distance from the scene, without a tube, so that he saw not only the tilted scene but the outer upright room as well. Under all three conditions the perceived vertical and horizontal were displaced significantly in the direction of the axes of the tilted scene. When an outer upright field was present, as in the third condition, the effect of the tilted scene upon the perceived upright diminished. In another experiment, judgments of the rod were obtained with body tilted, both to the same side as the field and to the opposite side. It was found that tilting the body resulted in an increased tendency to accept the tilted field as a basis for judging the upright. Not only were the perceived vertical and horizontal displaced further in the direction of the tilted scene, but a number of Ss perceived the tilted scene as fully upright. In another experiment there was found a tendency for the tilted scene to right itself with prolonged observation. In some cases the righting was complete, so that at the end of the observation period, the tilted scene was perceived to be fully upright. Under all conditions, striking individual differences were found in the extent to which the perceived upright was affected by the surrounding tilted field. There is evidence of considerably consistency in a person's performance under the different conditions employed.