Christine Ladd-Franklin

Born in Windsor, Connecticut, Christine Ladd-Franklin spent her early childhood in New York City. Her father was a prominent merchant, and her mother was a feminist. Following her mother's death when Ladd-Franklin was 13, she moved to Portsmouth, New Hampshire, to live with her paternal grandmother. Ladd-Franklin attended the Wesleyan Academy in Wilbraham, Massachusetts, for two years, taking classes with boys preparing to enter Harvard University, and was the valedictorian of her graduating class in 1865. After graduating from Vassar College in 1869 with a primary interest in mathematics and physics, she taught in secondary schools in Pennsylvania, New York, and Massachusetts for more than a decade. During this period, she also published numerous articles on mathematics. In 1878, she applied for admission to Johns Hopkins University for advanced study in mathematics. At that time, Johns Hopkins did not admit women. She signed her application with her first initial only and last name and was admitted because the admissions committee assumed she was a man. At Johns Hopkins, she studied under mathematician James Joseph Sylvester who believed her brain was more important than her gender. Because of her extraordinary intellectual ability, Ladd-Franklin was awarded the stipend of a fellow, although not the actual title because of her gender. Despite completing requirements for the doctorate in 1882, she was denied the degree until 1926.

At the completion of her fellowship in 1882, Ladd-Franklin married Fabian Franklin, a mathematics professor at Johns Hopkins University, and gave birth to two children, one of whom died in infancy. Atypically for married women of the time, and without a formal academic affiliation, she continued to publish scholarly papers, several of which appeared in the American Journal of Mathematics. After hearing Charles Sanders Peirce (1839–1914) lecture at Johns Hopkins, Ladd-Franklin became interested in symbolic logic and wrote a paper, “The Algebra of Logic,” which was published in 1883 in a book of essays by Peirce and his students. In her paper, praised as a landmark achievement by Harvard philosopher Josiah Royce (1815–1916), Ladd-Franklin reduced all syllogisms to a single formula, in which the three parts form an “inconsistent triad.”

Ladd-Franklin's mathematical interests ultimately led her to make important contributions to the field of psychology. In 1886, she became interested in the geometrical relationship between binocular vision and points in space and the following year published a paper on this topic in the first volume of the American Journal of Psychology. During the 1891–1892 academic year, Ladd-Franklin took advantage of her husband's sabbatical leave from Johns Hopkins and traveled to Europe to conduct research in color vision in the laboratories of Georg Müller (1850–1934) in Göttingen, and Hermann von Helmholtz (1821–1894) in Berlin, where she also attended lectures by Arthur König.

Opposing the prevailing three-color and opponentcolor explanations of color vision of the time, LaddFranklin developed an evolutionary theory that posited three stages in the development of color vision. Presenting her work at the International Congress of Psychology in London in 1892, she argued that black-white vision was the most primitive stage, since it occurs under the greatest variety of conditions, including under very low illumination and at the extreme edges of the visual field. The color white, she theorized, later became differentiated into blue and yellow, with yellow ultimately differentiated into red-green vision. Ladd-Franklin's theory was well-received and remained influential for some years, and its emphasis on evolution remained valid in the early twenty-first century.

After returning to the United States, Ladd-Franklin taught, lectured, and pursued research. She continued publishing and presented papers at meetings of both the American Philosophical Association and the American Psychological Association, as well as at international congresses. She lectured in philosophy and logic at Johns Hopkins between 1904 and 1909 and served as an associate editor in those fields for Baldwin's Dictionary of Philosophy and Psychology.

Moving to New York City with her husband in 1910 when he became an associate editor of the New York Evening Post, Ladd-Franklin began lecturing at Columbia University. She published an influential paper on the visual phenomenon known as blue arcs in 1926, when she was in her late seventies, and in 1929, a year before her death, a collection of her papers on vision was published under the title Colour and Colour Theories. In her writings and active correspondence with colleagues, Ladd-Franklin challenged the mores of the day, championing the cause of women in matters of equal rights, access to education and the professions, and the right to vote.