In 1928, William Moulton Marston conducted a public test of the apparatus he had developed to measure biometric changes in response to emotional stimulus, that would become the basis of his lie detector machines. His test subjects were eight chorus girls ("starlets") watching Greta Garbo and John Gilbert in Flesh and the Devil.
His aim was to test the hypothesis that blondes and brunettes responded differently to salacious movie content.
The Columbia Spectator duly reported the test methodology and Marston's hypothesis.
BLONDES, BRUNETTES DIFFER IN EMOTIONS Marston, of Psychology Department, Says Blondes React to Superficial Stimuli. Glandular differences between blondes and brunettes and between men and women are blamed for differences in emotional responses by William M. Marston of the Columbia psychology department. Blondes, he finds, have a greater reaction to superficial things, while brunettes are more lastingly impressed by love affairs and other situations.
Marston bases his conclusions on a study of some 7,500 men and women, including a group of* Staten Island school children and convicts in the Texas State Penitentiary. The subjects were examined by tests of their blood pressure, breathing and heart action.
... Certain experiments conducted at Radcliffe College showed interesting emotional differences between men and women. Women showed very little response when told that they were about to meet handsome young men, while the men, upon being introduced to the prettiest girls in Radcliffe, exhibited a fear reaction more than anything else.
A blonde will usually succumb quickly to amatory advances, he stated, and will not waste much time in attracting people of the opposite sex. A brunette, on the other hand, will exhibit a more lasting passion, and "would usually go the limit if she were out to have a love affair with a boy."
Boys are not so strongly affected by love affairs as girls, the findings show. They also show a tendency towards that type of response which Marston classes as "dominant". A test in which the experimenter talked to men about women showed a smaller response than the same test applied to women regarding men. A tremendous rise in blood pressure was observed in a Radcliffe girl when the conversation touched on rolled stockings.
Marston's book based on this hypothesis, The Emotions of Normal People was published in the same year. On this basis, he was briefly hired by Universal Studios as part of Hollywood's effort to recruit psychology to the cause of defending cinema against the economic cost of film censorship.