抄録
In case of both children and adults, the effects of time and space on velocity estimation in the field of motion perception are generally as follows: In constant physical velocity, subjective velocity increases with decrease in physical and/or phenomenal time and space (see Table 1). These effects may be tentatively explained by the neurophysiological adaptation hypothesis. Findings for the basis of the hypothesis are as follows. It has been reported that in comparatively primitive vertebrates such as frogs and rabbits, some ganglion cells in the retina respond only to a moving stimulus with certain direction, that when such cells are stimulated continuously by the moving stimulus, frequency of the neural discharge declines very quickly, and that in such cells the relation between frequency of the neural discharge and the angular velocity is expressed as an exponential function. These facts suggest that in pursuit movement of the eye a moving stimulus of a certain physical velocity with long exposure time raises sensory adaptation of certain directionally sensitive cells in the retina more strongly and frequency of the neuronal discharge in the cells accordingly decreases and then perceived velocity becomes lower than in the case of a moving stimulus of the same physical velocity but with short exposure time. But in higher mammals any such directionally sensitive cells have scarcely been found in the retina. Whereas those cells have, been found in the visual cortex of cats and monkys. It is therefore assumed that the same kind of neurophysiological adaptation for the moving stimulus might occur also in those cells in human visual cortex.
Now, we have made sure that effects of time, space and velocity on time and space estimations in the field of motion perception may be explained by the hypothesis of sets to choose cues in estimation. The present experiment is so designed as to make clear that in stead of the above hypothesis the neurophysiological adaptation hypothesis might hold better for velocity estimation.
For velocity estimation reproduction method was used. Standard stimuli shown in Table 2 consisted of the four series, each of which contained five standard velocities common to all series. In each series the condition of standard velocity 6.1cm/sec was the main condition and the other four were the additional conditions to a certain set. As the main condition and one of the additional conditions were alternately presented, reproduced velocities were obtained in four times for the main condition and only one reproduced velocity was obtained for each additional condition, in each subject.
The age and number of subjects are designated in Table 3.
The main results ware as follows:
1. Not only reproduced velocities under the main condition of the series TLL were lower than those under the series TSS for both children and adult, but also reproduced velocities under the main condition of the series ELL were lower than those under the series ESS for both children and adult (see Fig. 1, and Tables 4 and 5).
2. Ratios of reproduced velocities to standard velocities under the series TLL and TSS increased as standard velocities were higher, and those under the series ELL and ESS decreased a little as standard velocities were higher (see Fig. 2, and Tables 7 and 8).
These findings never agree with the estimates from the hypothesis of sets to choose cues in velocity estimation, but agrees pretty well with the estimates from the neurophysiological adaptation hypotheses.
