Apparent verticality following short-term sensory deprivation: Differential performances in young and old men

Abstract

The task of adjusting a luminescent rod to the apparent vertical, in a darkened room, was performed by 48 male S s evenly divided in two groups: young adults (from 19 to 30 years of age) and old men (from 65 to 86). Before testing, 6 Ss of each group were submitted to a definite duration of short-term sensory deprivation: i.e., 5 minutes (control condition), 2 or 3 hours (experimental conditions). The S lay on a bed, which was swiftly converted into an easy-chair at the end of deprivation session. The chair could be tilted sidewise, in such a way as to obtain three different body positions (30° left tilt; erect; 30° right tilt), wich were systematically combined with two initial positions of the rod (30° either in a clockwise or in a counterclockwise direction). On the basis of a 2 × 3 × 3 × 2 four-factor design (with repeated measures on the last two factors), analysis of variance was carried out on the experimental data. As regards young adults, the findings confirm the well known E-phenomenon and starting position effect: the apparent vertical shifts towards the opposite side of body tilt and towards the same side of initial position of the rod. Following 3 hours of sensory deprivation, the E-effect tends to increase. On the other hand, our aged Ss show the A-effect (i.e., a shift of the apparent vertical to the same side as body tilt), as well as a greater starting position effect than it occurs with young men. No significant changes are induced in old men's performance by short-term sensory deprivation.