Do baby tears have mind-control properties?
A few weeks ago, Israeli neuroscientists Shani Gelstein and Noam Sobel published a study about mind-control properties in human tears. The gist of the research, which enjoyed much media attention, is that women’s tears contain a chemical signal that reduces sexual desire in men. Tears were collected from the cheeks of emotionally-distraught women watching sad films and wiped on the upper lips of male volunteers. Compared to men who whiffed a salt solution control, the tear-sniffers not only had a reduced sex drive but also lower testosterone levels and reduced brain activity.
A leading explanation is that chemicals in tears generally reduce male aggression, making them more sympathetic.
How does this work? One theory is that one or more of the hundreds of chemicals in tears has “mind-control” properties, triggering specific predictable behaviors in others. (Here and here I write about how this happens in sweat, too.) One candidate is prolactin, a hormone associated with bonding. When inhaled in a person’s tears, prolactin may affect the sniffer’s hypothalamus, the part of the brain that produces hormones which in turn affect behavior.
Baby tears have not been the subject of a study yet (hopefully soon). But it’s not a far cry from certain that if there are chemicals in the tears of women that affect men, there are also chemical triggers in the tears of babies that affect their caregivers or anyone else that comes into contact with them. These tears may trigger care-giving instincts and reduce aggression toward the screaming infant.
I wonder: Infant abuse is relatively uncommon given how irritating a screaming baby can be. Are the people guilty of this crime more likely to be amnosiacs (loss of smell-sense) or have another form of brain damage that would prevent them from inhaling aggression-reducing signals in the baby’s tears?
Another theory: Kids cry all the time and sometimes it’s hard to tell when they really need attention. Might chemicals in emotional tears direct parents to respond appropriately when there is a real need for attention? Assume these chemical signals are only in emotional tears–not crocodile tears or sleepy-time tears. Do they help us intuitively know when it’s OK to let a child cry it out instead of rushing to soothe her?