Threshold value of a small continuous light increases as it approaches in distance to an inducing figure. CFF also becomes larger as a small flickering stimulus near the figure. However, these two results are opposing each other in terms of light sensitivity; since the raise of light threshold is the decrement of but the increase of CFF means the increment of light sensitivity. This discrepancy has not yet been explained. First of all, the light stimuli employed here are not identical in these procedures. Light threshold is determined by gradual darkening of a small continuous light; thus the stimulus has neither clear onset nor offset. On the other hand, CFF is measured by alternating a lighting period and a dark period; thus, the stimulus has its clear onset and offset. Recent work of the electroretinogrames of rods and cones indicates that a discrete light stimulus yields at least three different unit potentials: The on-potential at the beginning of illumination, the ordinary potential during illumination, and the offpotential immediately after the termination of illumination. And CFF is believed to be mainly depended upon the on- and off-potentials, while light threshold of continuous stimulus is related to the amount of the ordinary potential. It is also known that the off-potential tends to be larger in the light-adapted cone retina and to be sharper than the on-potential. Thus the obtained relationship between CFF and the distance between the flickering light and the inducing figure may be explained whether the on-reaction or off-reaction is more dominant in that test situation. It has been shown in the previous paper that Type A stimulus facilitates the on-reaction while Type B stimulus reinforces the off-reaction. (The former reaction is dominant under dark adaptation and the latter under light adaptation.) The Type A stimulus has a clear onset but it disappears gradually, and the Type B stimulus appears gradually, but it has a sharp offset. Evidently, when the inducing light stimulus is placed near the test figure, the retinal cells on which the test figure is projected are adapted by the light. When it is placed away from the figure, the stimulated cells are adapted to dark since the test figure is always visually fixated. Therefore, the purpose of this present study was to test whether or not the off-reaction becomes more dominant when the inducing figure approaches the test figure. The results obtained are shown in Tables 1, 2 and Fig. 6. Responces found in the centre of the human fovea changed from on-type to off-type as the inducing figure approached the fovea. This finding would explain why CFF is higher near the inducing figure and, consequently, why the sensitivity measured in terms of light threshold decreases while that of CFF increases as the inducing figure approaches the test figure. Additional experiments were carried out in order to explain the other two contradictions in sensitivity on the bases of the same principle. One is the initial rise in CFF or in apparent brightness as a function of luminance of the inducing figure, the other is the negative effect of the inducing figure. As shown in Figs. 8 and 9, these two contradictions were also explained on the basis of the very same principle.
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.
This report contains two experimental studies. These studies were undertaken for the purpose of verifying the hypothesis that the recognition of a letter located in different contexts shows the different results in recognition. In the first study, we used higher and lower contextually constrained sequences of letters as the stimuli, and in these stimuli the number of preceding letters were both four. In the second study, as the preceding letters we used 0, 2 and 4 letters respectively, and in all these experiments the response to the succeeding letter was examined. In the first study, the stimulus materials of lower contextually constrained sequences were obtained by selecting letters from the seventy-one Hira-liana letters using a table of random number, and those of the higher contextually constrained sequences were obtained by selecting letters according to their relative frequencies of occurence in sequences of five letters in Japanese. In the second study, the stimulus materials were obtained by the similar method as the first study. The findings resulting from these studies were as follows: (1) The recognition of the letter is influenced by the context in which it is located. Namely, when the higher contextually constrained sequences are exposed, the letter is recognized easily, but when the contextual constraint is lower, it is difficult to recognize the letter. (2) When the contextual constraint is higher, there are few errors on the recognition of letters, but when the contextual constraint is lower, there are many chances to respond erroneously. (3) The recognition of a letter is more influenced by the context, and the structural characteristics of a letter itself may be regarded as a secondary factor on it.
In order to retest the hypothesis advanced by Kimble & Bilodeau and supported by others that the joint effects of work and rest in cyclical motor learning are the simple summation of the two independent effects, 4 groups which represent each combination of two levels of work (15 or 30sec) and two levels of rest (5 or 30sec) variables practiced a task of printing over 16 min period. There was no significant interaction between the two variables, but a tendency toward interaction was observable in the second half period of practice. That is, the joint effect of simultaneous variation of both work and rest variables was a simple summation of the separate effects in the first half period of practice, but the work variable had a significantly higher effect than the rest variable on the second half. Of the two variables, the length of the rest period was more important. The relative importance, however, will depend on the kinds of task and the length of the two variables. The score differences produced by a variation in the amount of rest between trials are an increasing function of the amount of previous practice. The score differences due to the variation in the length of the practice trial became apparent at the 4 min practice although the amount was small, and stayed at a fairly constant level from that time on. The effect of changing the magnitude of one dose not depend upon the value of the other on the first half, but will be dependent upon each other on the second half. The hypothesis of independency and simple summation of work and rest variables was confirmed over shorter period of practice. With regard to the longer practice period, more data are needed to confirm the hypothesis. Thus it would be necessary to retest this hypothesis by extending the period of practice and the length of rest and work intervals.