Kurt Freund was a sex theorist and researcher. He was the first person to apply plethysmography, or the measurement of bloodflow, to studies of the penis. This work helped him created the penile plethysmograph, commonly known as the erection-detection machine.
Freund also contributed to discussions about a genetic link to homosexuality through his examination of identical twins, who almost always have the same sexual orientation. Influenced by his work "treating" homosexuals, he was one of the first psychiatrists to conclude that homosexuality was not a pathological condition. He worked hard to repeal anti-homosexuality laws in his native Czechoslovakia.
Kurt Freund died in Canada in 1996. He committed suicide during the advanced stages of lung cancer.