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Citation |
Cobb PW. J. Exp. Psychol. 1925; 8(2): 77-108. |
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Copyright |
(Copyright © 1925, American Psychological Association) |
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DOI |
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PMID |
unavailable |
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Abstract |
In 1923 the writer of the present article reported having found, in experimenting with the visibility of a black dot on a white screen, that the reciprocal of the exposure-time necessary that the dot should be seen was proportional, at least within certain limits, to the logarithm of the field brightness. The writer now reports a similar experiment, on the speed with which the retinal impression occurs. In this case the law seems to be "… that the reciprocal of the threshold time increases equally with equal increases in the logarithm of the brightness." The effect of pre- and post-exposure patterns was to increase the threshold time; a constant increase in the size of all the stimuli tended to reduce it to a minimum. The writer points out that since there were rather wide individual variations among his seven subjects his average values "… may be considered only relatively, as with reference to changes in threshold time or 'speed' with changes in brightness." From Psych Bulletin 23:02:00030. (PsycINFO Database Record (c) 2012 APA, all rights reserved) |