This might be useful in certain circumstances:
Scientists have known for more than a half-century that our pupils dilate whenever we see something we find sexually arousing. This is a non-voluntary response that is controlled by the autonomic nervous system—the body system that controls other automatic responses like heart rate, respiration, and digestion. As a result, it’s not something that people can consciously control, so it gets around the problems of people lying on surveys and faking genital responses.
a new set of studies published in the Journal of Sex Research finds that—among men—pupil dilation doesn’t just reveal the gender of the people they’re attracted to, but also their age.
when viewing images of children, no increase in pupil size was observed for men in any sexual orientation group. In fact, if anything, their pupils actually had a tendency to constrict when viewing kids. The results of all of these studies suggest that pupil dilation holds a lot of promise as a technique for measuring attraction based on both gender and age.
it could also be quite useful to forensic researchers who study pedophilia and other sexual interests that people are strongly motivated to conceal.
It’s not mind reading, but it might be close enough to make life safer for your kids in some situations.