When I first saw photographs of John Boehner, the new House Speaker, crying at the drop of a hat when he took up the gavel, I paused to wonder if he had come up with a new form of mind control. If so, the lachrymose Congressman has embarked on a brand new offensive in National politics.
All joking aside, now comes news from the journal Science that tears contain imperceptible chemical signals that unconsciously influence the behavior of others. There is evidence that they can alter an observer's thoughts, too.
Consider first that the same lachrymal glands are able to secrete different kinds of tears. There are tears of joy, tears of grief, crocodile tears of deception, and physical pain that brings tears to our eyes. For a long time we have known that emotional tears are chemically different in composition from those produced, say, by irritation or a cold. The mystery was why. Evolution must have a purpose for them given that ocular secretions in most other mammals exert social effects such as bonding and aggression.
For ages, poets and philosophers assumed that one's reaction to weeping was a sympathetic, kindhearted response. Tennyson questioned its purpose, "Tears, idle tears, I know not what they mean," but Alexander Pope was on to something when he sensed that tears had an intended target, "Accept these grateful tears! for thee they flow, / For thee, that ever felt another's woe!"
A women's tears that can tame a tyrant were long thought of in terms of a visual trigger, but crying is more than meets the eye. Dr Noam Sobel has found a chemical signal in tears that inhibits testosterone in men. Though usually thought of in terms of sex drive, the principal male hormone influences a variety of things from mood to the maintenance of muscle mass. It is one busy molecule, stimulating blood cell production, fat breakdown, RNA synthesis, and the balance of essential elements. The brain happens to be loaded with testosterone receptors.
Which brings me to a favorite trick called volume transmission: signaling throughout the nervous system by small molecules. If you think of the brain's wiring of neurons and synapses as a train going down a track, then volume transmission is the train leaving the track! Functional MRI images show that undetectable odors such as androstenedione affect behavior unconsciously by altering glucose metabolism in structures that modulate attention and emotion.
The odorless molecules in tears that tap into unconscious cognition belong to the group known as pheromones. They are similar to messenger signals in urine and those secreted by the apocrine sweat glands around the armpit, groin, eyelids, and anus that become active at puberty.
MRI images Dr. Sobel took while exposing men to female tears had diminished activity in areas concerned with sexual arousal. Even hard-wired physiology like heart rate, skin temperature, and breathing fell. Finding testosterone as a target of tears suggests that oxytocin, which affects social bonding, will likely be one, too. Time will probably turn up additional chemical messengers.
Now that we know about pheromone signals in women's tears, and that these are imperceptible to observers through the ordinary senses, it is likely that we'll find the tears of men and children to contain unique pheromones of their own.
In fact, Dr. Sobel's research group has begun looking at how men's tears unconsciously affect women and other men. The results will take some time. In the meantime, keep your eye on John Boehner and see if he changes any minds—maybe even your own.
View a video gallery of the lacrymose Congressman