As the researchers leading the study pointed out, these beliefs were not based on evidence.
Dr Margareta Tornqvist, who was leading the study, investigated dozens of possibilities before testing food.
"They are all fine and being monitored regularly by the medical team leading the study," it said on Thursday.
That relationship seems to be weaker in urban Chicago than in smaller towns, said Julie L. Davis, the university's community research coordinator and who is leading the study.
The team leading the study published in the journal Learning, Media and Technologyy' suggest that "our ability to function optimally [and learn], varies with biological time rather than conventional social times".
Richard Anderson, a professor of clinical reproductive science at the University of Edinburgh, who is leading the study, said the method was expected to be more effective than condoms, which in real-life conditions are about 82% effective.
"We will look at how the social structures and social behaviour of the whales influences the evolution of menopause and the animals' survival," said Dr Dan Franks of York University, who is also leading the study.
Dan Bloom of MDRC, a research group based in New York that is leading the study, said, "It's very promising, but it's also early," adding that the numbers will change as graduates are followed.
Anne Germain, a Canadian sleep researcher who is leading the study, told me, "It's fascinating to me how people can change the content of a nightmare to a non-nightmare.
"It really does frighten me a lot if people coming into contact with those women and children aren't disclosing their status out of fear of being perceived as bad parents," Harman, who is leading the study, said.
