0000000000306907
AUTHOR
Mark F. Tritsch
The veridical perception of object temperature with varying skin temperature.
The effect of skin-adaptation temperature on object-temperature perception was investigated, using the method of dichiric matching, in an attempt to determine whether veridical perception of physical object temperature occurs in human subjects. Observers were presented with a test temperature on one hand and required to find a matching temperature, that is, one that produced the same sensation, on the other, differently adapted, hand. Using equality of test and matching temperatures as a criterion of veridical perception, it was found that the latter improves with ΔT, the difference between object temperature and skin-adaptation temperature. It is postulated that when ΔT is close to zero, v…
Fourier analysis of the stimuli for pattern-induced flicker colors.
Pattern-induced flicker colors (PIFCs) were observed and color matched in rotating discs from which higher-harmonic Fourier components in the square-wave temporal luminance functions of a conventional black-and-white Benham disc had been removed. Since both reddish-brown and blue PIFCs were visible with purely sinusoidal stimuli they cannot result from differences in temporal stimulus shape or pattern and do not provide evidence for a temporal coding theory of color. Green PIFCs differed in that they did require the presence of additional harmonics. In a second experiment the luminance means upon which the sinusoidal PIFC stimuli were imposed were varied. The results show that color is dete…
Erhöhte Schwellen für die Detektion von Phasenunterschieden in musterinduzierten Flimmerfarben bei Patienten mit Glaukom
BACKGROUND: Pattern-induced flicker-colors are subjective colors produced by rotating disks with black-and-white arcs. Changing the direction of rotation results in a different color. Small variations in the temporal sequence (phase differences) of the black-and-white pattern cause the colors to vary and can be perceived as color differences. PATIENTS AND METHODS: We investigated the thresholds for such phase differences in healthy (n = 11) and in glaucomatous (n = 19) eyes. Acuity and color vision were tested and in patients static visual field perimetry (Octopus G1) was carried out. The disks used for producing the pattern-induced flicker-colors were viewed from a distance of 2 m and had …
Color discrimination under mesopic conditions in cats and humans
The ability to discriminate colors under various levels of mesopic illumination was studied in three cats using colored papers as stimuli and with a computer controlled training schedule. Discrimination based on brightness differences was prevented using a new method in which illuminant color was varied. The luminance threshold for color discrimination in cats was found to be 0.5 cd/m2, close to the cone threshold reported by others from ganglion cell recordings. The same experiment was carried out with human subjects and revealed a luminance threshold of 0.00042 cd/m2 for color discrimination.
Color induction via non-opponent lateral interactions in the human retina
Retinal connections causing colors in Benham's top (pattern induced flicker colors, PIFCs) are investigated by psychophysical experiments. PIFCs are still seen when stimuli to different cones are demodulated selectively, indicating the involvement of non-opponent channels. PIFCs also occur on retinal areas next to those affected by modulated stimuli; further, both monochromat and dark-adapted trichromats perceive PIFCs which are achromatic. These additional findings point to horizontal cells as neuronal mediators of modulated excitation leading to PIFCs. The unspecifity of the postulated connection with respect to cone types agrees with anatomic findings of Boycott, B. B., Hopkins, J. M. an…