Cold Sweat

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The pheromone debate rages on, with one large consumer-products company manufacturing soap supposedly laden with the li’l devils. (Read all about it here.) Now, truth be told, I’m not so sure I’d want to walk around exuding subliminal signals that say, “C’mere, stranger!” but the MBA’s who develop these products seem to think I would, and you would, so there ya go: the geniuses of American business are at it again!

A couple of things: it’s not at all certain that human pheromones even exist. Animals have a special organ which perceives them; if you’ve ever seen a cat lift its head, open its mouth slightly, draw its lips back and mouth-breathe the air with a vacant expression, you’ve seen it -- the pheromone-detecting organ (VNO) at work. Some researchers think we have them. Others say we don’t. Others think we might, but vestigial, like the appendix.

Sweat, until recently, was just thought to be well, sweat. But there are different kinds of sweat. There is exertion sweat, and emotion sweat. Here’s the best part; the nose can’t tell them apart, if they’re fresh, but the brain can.

In 2009 a team of researchers, funded mostly by the military (are you surprised?) published a quite comprehensive study about the subliminal perception of fear-sweat. They looked at eighty presumably sane people who had signed up for sky-diving lessons. Somehow, the research team convinced these subjects to shave their armpits, control their diet prior to the study, and wear collection devices before, during and immediately after their first jump, done in tandem so they wouldn’t have to move (exert themselves) much, thereby reducing exertion sweat.

The collected apocrine sweat, analyzed by gas chronograph, showed significant amounts of androstadienones and androstenones, compounds reputed to be involved with human reproduction. Aha!

The jumpers and their sweat were put through every imaginable test to rule out what in research is called the “confounding variable.” (If you would like to read the original paper, do so here.) The gist of the research was this: the subjects -- those smelling the collected sweat -- were tested inside a Functional MRI, which “looks” at an active brain in real time, using magnetic imaging. If the methodology is good, and this was, it is the purest, most accurate way to determine what is really going on in the brain and reach the most accurate conclusion.

The areas that lit up in these subjects were in the left brain, specifically in the left corticoid amygdala. The amygdala is a referee of sensory signals and emotional reactions. It modulates, coordinates and ultimately delegates. It is one of the most crucial brain structures, as it links the “old” (primitive) brain with the “new” (cortex) thinking/interpreting one.

The research team then came up with an interesting way to look at how this innocuous substance (remember, the subjects couldn’t smell “sweat” consciously) might affect fear perception in the smeller. They took a series of morphed images of facial expression, which ranged from neutral to ambiguous to fearful, and showed them to the subjects which had or had not been smelling the fear-sweat from the jumpers. The subjects who had been showed significantly sharpened perception; in other words, you might say their vigilance was heightened. What this means is that their brains were put on alert, even though the smellers were not consciously aware of that.

This kind of thing has obvious applications for all kinds of interesting investigation, especially for the military. They also say that more research is needed, as they’d like to look at this kind of brain arousal in conjunction with other kinds of facial expression.

If you really wanted to stretch, I suppose you could call these sweat substances -- androstadienones and andostenones -- “pheromones,” but these researchers don’t. There is another study, not nearly as comprehensive (or as well-funded, I’d guess) as this, which concludes that women can tell the difference between sweat from sexually aroused males and those who are not. Now, if somebody could come up with a way to isolate those same compounds from females, then they’d have something! Can you imagine the big perfume manufacturers just falling all over themselves to get at it?

Back to the soap company. The “pheromones” they supposedly isolated came from good ol’ garden-variety sweat, apparently. Not the sweat of terrified skydivers or aroused males. Research this good is, apparently, hard to find.

But not that hard.




The original article, “Chemosensory Cues to Conspecific Emotional Stress Activate Amygdala in Humans” was published in 2009. Copyright 2009 Mujica-Parodi, L.R. et al including Strey HH, Frederick B, Savoy R, Cox D, et.al, used under open-access status, Creative Commons Attribution License.

Photo copyright Drazen Vukelic, Dreamstime.com,used under license