in the periphery
Ewald Hering
Reprinted by permission of Open Court Publishing Company, a division of
Carcus Publishing Company, from Philosophical Portrait Series, © 1898 by
Open Court Publishing Company.
EARLY DEVELOPMENTS IN PHYSIOLOGY AND THE RISE OF EXPERIMENTAL PSYCHOLOGY 243
of the retina, night vision and movement perception
are better than in the fovea. Ladd-Franklin
assumed that peripheral vision (provided by the
rods of the retina) was more primitive than foveal
vision (provided by the cones of the retina) because
night vision and movement detection are crucial for
survival. But if color vision evolved later than achromatic
vision, was it not possible that color vision
itself evolved in progressive stages?
After carefully studying the established color
zones on the retina and the facts of color blindness,
Ladd-Franklin concluded that color vision evolved
in three stages. Achromatic vision came first, then
blue-yellow sensitivity, and finally red-green sensitivity.
The assumption that the last to evolve would
be the most fragile explains the prevalence of redgreen
color blindness. Blue-yellow color blindness
is less frequent because it evolved earlier and is less
likely to be defective. Achromatic vision is the oldest
and therefore the most difficult to disrupt.
Ladd-Franklin, of course, was aware of
Helmholtz’s and Hering’s theories, and, although
she preferred Hering’s theory, her theory was not
offered in opposition to either. Rather, she attempted
to explain in evolutionary terms the origins
of the anatomy of the eye and its visual
abilities.
After initial popularity, Ladd-Franklin’s theory
fell into neglect, perhaps because she did not have
adequate research facilities available to her. Some
believe, however, that her analysis of color vision
still has validity (see, for example, Hurvich, 1971).
For interesting biographical sketches of LaddFranklin,
see Furumoto (1992) and Scarborough
and Furumoto (1987).