Abstract
W. S. Stiles, in a series of classic studies (Stiles, 1939; 1949; 1953; 1959; 1978) developed the two-color increment threshold technique, and applied it to the analysis of the mechanisms of color vision. In Stiles’s procedure an observer is adapted successively to each of a series of increasingly intense exposures of a large field of one wavelength (μ), and the threshold is measured for a relatively small and brief test of another wavelength (λ) presented in the center of the adapting field. The resulting data are plotted as an increment threshold curve or threshold-vs. intensity (t.v.i.) curve, giving log Uλ, the logarithm of the threshold intensity as a function of log Wμ, the logarithm of the background intensity. Even if the test target is confined to the fovea, the full increment threshold curve usually is found to be composed of two or more distinct component regions or “branches”, much as parafoveal dark adaptation curves normally comprise two distinct component regions.
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Pugh, E.N., Thornton, J.E., Friedman, L.J., Yim, M.H. (1985). Stile’s π 1 and π 2 Colour Mechanisms: Isolation of a Blue/Yellow Pathway in Normals and Dichromats. In: Ottoson, D., Zeki, S. (eds) Central and Peripheral Mechanisms of Colour Vision. Wenner-Gren Center International Symposium Series. Palgrave Macmillan, London. https://doi.org/10.1007/978-1-349-08020-5_8
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DOI: https://doi.org/10.1007/978-1-349-08020-5_8
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