The time of perception as a measure of differences in sensations / by Vivian Allen Charles Henmon.

  • Henmon, Vivian Allen Charles (V. A. C.), 1877-
Date:
1906
Catalogue details

Licence: In copyright

Credit: The time of perception as a measure of differences in sensations / by Vivian Allen Charles Henmon. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    individuals of normal color vision and on color-blind persons the limits can be definitely fixed, and this will then make possible a convenient method of measuring the color sense. This is one of the valuable features of the method that it furnishes a means of measuring rather exactly individual differences in color perception, and not only the fact of color deficiency, but the degree of the deficiency as well. Tests, which do not appear in the tables, on persons of supposedly normal color vision show this and give ground for the belief that a reduction in the color sense is more common than is usually supposed, and that there are all degrees of ability to discriminate colors, ranging from the highest discriminativeness down through the reduction in color sense to the extreme forms of color-blindness where the confusions are numerous and marked. It is, I think, mainly held that the color- blind form a separate species marked off from those of normal color vision. It seems to me that this is not the case, but that the color- blind form the lower end of a normal distribution curve. This method combines the methods based on the confusion of colors with a measure of the time of perception. This becomes apparent when one correlates with the results in Table XI the errors made. Wherever in the table the differences are small between the times for the blues and yellows and the reds and greens this is due in a large measure to the errors and confusions in the reds and greens, which would disclose a defect. Thus, in Series I on subject, K, who is red- green blind, there were many errors both in the discrimination of the reds or greens and in the confusion of reds and greens, especially the light red, which is a rose red approximating Holmgren’s standard, and the dark green. In Series III, however, on the same subject all the reds and greens were correctly distributed, but the time is much longer. In all cases with this subject the differences could be noticed with careful inspection. Of the fifteen series taken, in eight no errors were made and in all but three the errors seemed to be of a chance character. On running over the results of a distribution he could readily detect an error when the colors were side by side. Subject L is distinctly red-blind. There is no confusion of the reds and greens, but a difficulty in discriminating reds, which are ap- parently not distinguished from other colors of equal brightness. Thus lavender, purple and pink seem to him to be shades of blue. A light green-blue, Milton-Bradley’s tint No. 2, is not distinguished from pink. In the case of subject Tj, the difference in time is greater than in the two subjects K and L, which would appear to indicate a greater degree of deficiency. This is due to the fact that no errors were made after the third series. In the first three there was some difficulty in