AN EXPERIMENTAL STUDY ON CONDITIONS OF MEASUREMENT IN PERCEPTION OF SPACE DISTANCE (1)

Abstract

When the magnitude of the field-force is measured by the perceived space distance, it is often observed that the measured values of control figures are also under similar influence. It might be expected therefore that the conditions of measurement and the dispositions of figures may exert a great influence on the measurement of perceived space distance, if any minute variations are measured by the method of adjustment. Verification of this effect would be useful for the precise measurement of the opticalillusions involving the distance and size of various figures.
In this experiment, the following two conditions were studied extensively; 1. the conditions of measurement and 2. the dispositions of figures. They were analyzed by a simple procedure in which the space distance between two points were measured by another two points. Four test-distances, 3, 10, 30 and 80mm, were selected in order to find the trend in the constant errors with the variation of the space distances in the standard stimulus. The conditions of measurement include the following five alternatives; 1. the condition of observation (binocular or monocular observation), 2. the distance of observation (1m, or 2m), 3. the method of observation (free viewing or with fixation), 4. the space order of the figures (first space order or second space order), and 5. the method of measurements (the method of adjustment or the method of limits). For the purpose of analyzing the effect of the dispositions of figures, three sorts of disposition were selected out of the several which were usually employed in changing the space distance between two horizontally placed points
Results. 1. The constant error appears to have resulted in either overestimation or underestimation. Furthermore, as the space distance of the standard stimulus increased, the changes of constant error produced a certain pattern of alternations. 2. In the free viewing condition, the constant error was scarcely influenced by the variation in the condition of observation, the distance of observation, and the method of measurement. 3. In the fixation condinion, the constant error resulted in overestimation, and the overestimation increased following a certain tendency. 4. In the second space order, the constant error resulted in overestimation, and the different method of observation did not influence the constant error. 5. Refer to the Fig. 6, a, b, and c. With both methods of observation, the difference in the disposition of the figures did not result in any alternations of tendency in the constant error. However, in the fixation condition, the constant error of the case a was the maximum.
It may be concluded that the difference in the method of observation and that of the space order of figures alter the perception of the space distance remarkably, even in such simple conditions as measuring the space distance between two points by another two points in the limited visual field.