I read about a study of serotonin that was made on mices. The levels of serotonin was manipulated with the help of diets rich in tryptophan aminoacid and in diets without. The result of the study showed something amaising. The mouse that didnt had a diet rich in tryptophan [that of course means low leves of serotonin] was turned in a bisexual mouse. This study made waves in the science comunity regarding gay people.