Recently, random-dot stereograms (RDS) have been widely used as a test of stereopsis. In the present study, we analysed small vergence eye-movement in an RDS test, using an infrared fundus haploscope. Two types of RDS were used: one with a crossed disparity of 14', and another with an uncrossed disparity of the same visual angle. For the RDS with crossed disparity, the angle of convergence changed by approximately 40' when the fixation point moved from the floating central area to the surrounding area. On the other hand, for the RDS with uncrossed disparity, the convergence angle changed by about 25' when the fixation point moved from the recessed central area to the surround. For the strabismic patients, the RDS was presented dichoptically in accord with their angle of squint, and the fusional vergence movement was video-taped. A large portion of the exotropias (50%) were only able to fuse the RDS incompletely, while showing a stereoacuity of better than 80" on the Titmus Circle Test and New Stereo Test. Furthermore, eight subjects from this group (90%) showed a vergence eye-movement defect. These results suggest that fine control of active vergence eye-movement is required for the RDS test.
Field facilitation refers to the phenomenon in which thresholds for a test stimulus obtained on an adapting field, F_1, tends to decrease when the second field, F_2, is superimposed on F_1, if their colors are opponent to each other. This has often been ascribed to "depolarization" of an opponent-color system. In the present study, detection thresholds for a red test stimulus of a 200 ms-duration and 40'-dia were obtained on a steady red adapting field of a fixed intensity, on which a green second field of various intensities was superimposed. The green field was presented for 3s, and the stimulus onset asynchrony (SOA) between this field and the test stimulus was varied systematically. The results of two subjects show that field facilitation critically depends on SOA, i.e. it vanishes at the SOAs shorter than about 100ms. Those results suggest that the opponentcolor system, r-g system here, should take approximately 100ms for depolarization in the present stimulus condition.
A text was presented in one of three modalities (auditory, visual, or audiovisual) at fast or slow rate. Modality difference of recall performance was observed only in the fast rate condition. And this modality effect was auditory superiority over visual and audiovisual presentation. Visual inferiority was interpreted in terms of the necessity of translation. It is supposed that the translation from visual input into an acoustic form consumes some time and it leads to processing insufficiency when presentation rate is fast. Visual inferiority is found also in the processing of word-lists, while audiovisual inferiority is peculiar to text processing. From the deterioration of audiovisual performance at fast presentation rate, the visual component of audiovisual presentation also seems to be translated acoustically during text processing.
In the present paper several theories which might be applicable to the problem of lightness constancy were briefly reviewed. First, it was argued whether perceived lightness could be adequately explained by the luminance ratio principle which suggests that the stimulus correlate of perceived lightness of an achromatic surface is to be found in its ratios to the surrounding in luminance. It was discussed that perceived lightness could not be completely explained by luminance ratio at the retinal level. In the second place, the problem of lightness constancy was discussed from the view-point of the relationship between perceived lightness and perceived illumination. Then, it was suggested that perceived lightness is intimately related to perceived illumination, but the causal relations between these perceptual properties which are suggested by the taking-into-account theory could not be found. And, after all, these percept-percept relationship has important implication for perceptual theory of lightness.