図-地反転の実験的研究 I

持続提示における面積, 意志的統禦ならびに長時間持続観察の効果

抄録

The effects of area, voluntary control and prolonged observation on the figureground reversal were analysed by the continuous presentation method.
The stimulus used was a circle divided into six sectors (Fig. 1). The following measures were adopted for the record and analysis of reversal process : total time of appearances for two shapes (T_α, T_β), total undefined time (T_ε=T-(T_α+T_β)), the number of appearance (n_α, n_β), relative dominancy (R=100T_α / (T_α+T_β)), average duration (t_α=T_α / n_α, t_β=T_β / n_β) and the frequency of first appearance (f_α, f_β).
By varying the sector angles of two shapes, we obtained quantitative relationships between the sector angle and each measure (Table 1, 2, 3, 4 ; Fig. 2, 3). Smaller shape appeared as “figure” more frequently at first view, persisted longer in reversal and was more dominant in the total time of appearance. The larger the areal difference of the two shapes was the stronger were these tendencies, and the slower was the reversal.
By voluntary control, the relative dominancy (R) could be changed to some extent (Table 5). The amounts of shifts of R were almost equal in the three stimuli with various sector angles, but were different in two directions (increasing and decreasing). These shifts of R were based upon the changes in both T_α and T_β, which, in turn, were depended mostly on the changes in t_α and t_β.
The prolonged observation (12min.) did not cause the acceleration of the rate of reversal which had been expected by Köhler (11). On the other hand, the prolonged observation resulted in the increase of the undefined time and the decrease of the favourable shape, and the slight shift of R to the neutral point (50).