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.

    18/80 (page 18)
    For convenience, I shall call them hereafter orange-red^®, orange- red®® and orange-red^®, using in the tables the abbreviations OR^®, OR®® and OR^®. The first, OR^®, was secured from a mixture of vermilion and mineral orange; the remaining two from vermilion and chrome yellow. This gives a very satisfactory series of colors. Aside from the normal difference in brightness or luminosity, the only difference that could be noted was that of color-tone. There were no other differences apparent which might serve as cues in discrimination. The determination of the position of each color-tone in the scale be- tween orange and red was made with color wheels and is thus subject to a small error of observation. In order to reduce this to a minimum, the equations were determined on a basis of the judgments of at least five persons connected with the psychological laboratory, and were repeated until it seemed certain that the proper hues had been ob- tained. Tests were made on different days and with the normal varying light conditions of diffuse daylight. The wave-lengths of these colors, intermediate between orange, 614/z/z, and red, 639.5/z//, are thus 620.375/z/z, 626.75/t/i and 633.125///i. This statement of the wave-lengths is based on calculations from the standards and not from actual determinations. From the papers secured squares 3x3 cm. were cut and mounted side by side on black cards, each together with a corresponding square of standard red. The colored surfaces were thus 6x3 cm. in area. The series consisted of red together with yellow, orange, orange-red^®, orange-red®® and orange-red^®. The apparatus by means of which these cards were exposed was that devised by Cattell and used by him in the experiments referred to above. A brief description will be given here. It consisted of a black wooden frame, 39x39 cm., in the center of which is an aperture 6 cm. in width and 3 cm. in height. That part of the frame which surrounds the aperture is so cut as to prevent shadows being thrown on any stimuli exposed. The drop-screen has an especial feature which makes it very valuable for experiments such as are to be de- scribed. The screen by means of which the aperture is exposed is of aluminium and is drawn down by a spiral spring. The exposure is practically instantaneous, the eye being unable to follow the screen as it drops. The rate of motion when the exposure is made is about 10 m. per second, and the card is thus uncovered in 3<r. The cards are fitted into a shutter which runs in a horizontal track behind the screen. The screen, when the aperture is closed, is held in place by a lever to which a spring is attached. A small rod is fitted on the screen between the prongs of a fork, which breaks or closes the circuit as the screen is raised or dropped. Simultaneously with the exposure of the card, the electric circuit is closed.