視知覚における形の場の理論の実験的分析

横瀬のポテンシャル場の理論式の検討

抄録

Problem. According to previous experiments, the effect of the figure upon the c.f.f of a flickering point on the ground proved to follow the next rules.
(1) The effect decreases with an increase in the distance from the figure to the test point.
(2) The effect increases within a certain limit with an increase in the light-intensity of the figure.
(3) The disposition of the effect of the fringe of the figure depends on the structural character of the figure.
The experimental curves obtained so far under various figural conditions have shown the tendency considerably similar to that of the theoretical curves obtainable both from Yokose's theoretical formula of the potential field and from Uchiyama's empirical formula under the corresponding figural conditions.
We have then attempted an investigation, using the flicker method, to test statistically the function of the distance from the figure, the light-intensity of the figure, the subjects used (individual difference), the repetition of measurement and the interactions between these factors.
Procedure. The dark-adapted subject was presented with a light-figure in the dark room and the c.f.f. of the flickering point projected on the ground was measured.
The effect of the figure on the ground was estimated by the following equation:
δ=100⋅(i-i₀)/i₀
where i₀ is the c.f.f. value in case of no influencing figure and i is the c.f.f. value with one.
The stimulus figures were contoured circles 4, 6.5, 9 and 14mm in semidiameter, illuminated at varied intensities 1, 10, 100 and 500 radlux. A flickering point 2mm in diameter was projected in the center of each circle.
Results. Supposing that the δ-effect is an integration of the effects of the minute parts of the figure and the effect of the minute part is inversely proportional to the α power of the distance, we can formulate the following functional relation between the δ-effect and the distance (D):
logδ=log2πc(α-1)logD
where c denotes a constant and D corresponds to the semidiameter of each circle.
Then we calculated α and c by the method of least squares in regard to each of the light intensities, of the subjects and of the measurements of our data. The obtained mean and standard deviation of α were respectively 2.04 and 0.45. There was no significant difference of α at the 1 per cent level within the light-intensities, the subjects and the measurements.
We have further investigated the relation between c and the light-intensity (H). We supposed
logc=βlogH+γ
and computed β and γ by the method of least squares in regard to each subject and each measurement repeated. The mean and SD of β were respectively 0.11 and 0.13. These obtained figures indicate that there could hardly be established any definite functional relation between the δ-effect and the light-intensity.
On the other hand, it may safely be assumed from our experimental data that the individual difference is larger under the weaker stimulus conditions than under the stronger ones and that the repetition of measurement reduces some fluctuations of the data.
The above facts were also confirmed in our experiments conducted under the same figural conditions by the method of light stimulus thresholds.