Trust the science. Don’t trust the hype

The Scent of a Woman: Don’t trust the hype about pheromones and sexual attraction.

“Doty refers to a 2004 study on sheep that interrogated the long-held assumption that females ovulate in the presence of males, most likely due to pheromones. The researchers put lavender on the males and after a few mating sessions, the females began ovulating from the scent of lavender alone. The findings suggest that the females’ hormonal response was an acquired behavior, rather than an innate one.”

In the excerpt quoted above, Doty or an ignorant article author turned the effect of pheromones on luteinizing hormone (LH) into an acquired behavior due to lavender. Trust me, or read it yourself: The 2004 study on sheep demonstrates that ewes learn to associate lavender odor with their sexual partner. A 2010 study shows this association is made via an effect on LH. A 2011 study reports that the effect on LH is linked to testosterone levels of the male, and results soon to be published show the effect of the testosterone-associated pheromones on female behavior is not due to the visual appeal of the male, and that sexual experience is not required (in goats).

Where’s the hype about pheromones that you can’t trust? Four additional studies show exactly the opposite of what we’re told in the article. It’s the pheromones that alter LH and behavior in the sheep (and all other mammals). The effect of food odor on LH is not due to the visual appeal of the food, either.

Trust the science!

Androstenol effects LH in women. It is found in male axillary secretions, which influence LH and mood in women.

We used a mixture of androstenol (which effects LH), and androsterone, (which is an indicator of testosterone levels), to make a man more visually appealing. Earlier this year, our results were presented to other scientists at the Association for Chemoreception Sciences conference. We showed that a mixture of androstenol and androsterone increased women’s observed flirtatious behavior and their self-reported level of attraction. Our results indicate androsterone, which is associated with testosterone levels in human males, affects behavior during 15-minutes of exposure in a typical social circumstance.

Those who understand anything about the biology of behavior will recognize the suspected effect on LH and the demonstrable behavioral affect are expected when testing either food odors or social odors. The social odors are pheromones. Adding human pheromones (specifically, our mixture of androstenol and androsterone) increases sex appeal the same way adding spice increases the appeal of food. Not everyone will respond favorably to all pheromones or all spices, but the effect on hormones and affects on behavior are very predictable. Only a fool would argue against cause and effect with regard to pheromones in any species.

Who’s fooling who about human pheromones, sexual attraction, and who you can trust?

Pheromones and falling in love (circa 1974)

I rediscovered this citation while searching for information on neural pathways that influence the secretion of gonadotropin releasing hormone (GnRH). That’s how mammalian pheromones influence our behavior, which doesn’t happen in Kallmann’s syndrome. It’s a syndrome associated with congenital anosmia. Infants are born with no sense of smell, and there are other symptoms to be considered. You can find details elsewhere. My point, today, is that most researchers were largely unaware (in 1974) that there might be human pheromones. But these guys suggest their involvement in falling in love. (I love it!) Here are my notes;  the quotes are substantially informative.

“I would like to mention specifically Kallmann’s syndrome, which can open up a Pandora’s box.”

“There is a word we have not mentioned in this conference so far: pheromones.  We really had better not only mention it, but start thinking about it if we are going to deal with puberty.”

“…the very deficit that created gonadotropin deficiency also does something else up there in the hypothalamus; i.e., one has a deficiency also with regard to…” … falling in love.

Kulin, H.E., & Reiter, E.O. (1974) Hypothalamic‑pituitary regulation of puberty in man. Evidence and concepts derived from clinical research (discussion) In: Grumbach, M.M., Grave, G.D., & Mayer, F.E., (eds.) Control of the Onset of Puberty. (pages 264‑265) New York: Wiley.

The Demise of Guys

From a discussion about the new American Society of Addiction Medicine definition of addiction comes this 5-minute long humorous, albeit somewhat alarming, video clip providing insight on “the dopamine hypothesis.” Currently, few people realize that the dopamine hypothesis is merely an underdeveloped explanation of neurophysiological cause and effect because no associated environmental stimulus directly effects a neuroendocrine response which links the stimulus to behavior. People think that visual input directly effects dopamine, but no evidence suggests a neurophysiological mechanism that would allow this direct effect. Most of the visitors here will probably need to wait until other researchers learn its the link from food odors and social odors (i.e., pheromones) that gives the dopamine hypothesis its credibility via the effect of odors on a cascade of hormones that begins with gonadotropin releasing hormone (GnRH). But until then, you can still enjoy the video.

Men and women who stare at goats…

…in attempts to determine the cause of their sexual behavior.

Estrous female goats use testosterone-dependent cues to assess mates The testosterone-dependent assessment cues are associated with scent marking or courtship behavior. In a subsequent study, these researchers looked only at the testosterone-dependent assessment cues that were associated with courtship behavior. That is, they looked only at associated visual cues.

Their results are not surprising:  Female goats use courtship display as an honest indicator of male quality. Testosterone dependent courtship display is important. But the design of the second study eliminates testosterone-dependent assessment cues associated with scent. Thus, secondary results are reported only on one of the two important variables that were initially reported. This selective reporting helps to ensure a false conclusion about what is responsible for mate assessment. Testosterone-dependent scent that was initially important is now not even considered to be important enough to compare it to the importance of visual cues seen by the female during courtship behavior.

Comparatively speaking, telling us visual cues are responsible for mate assessment is like telling us apples appeal to us because they look good. If true, there is no further need to determine the chemical or chemicals involved in establishing an apple’s odor appeal. But it’s not true.

Why does an apple look good? Certainly, good-looking apples do not “behave” differently than those that do not look as good, so why would we choose the best looking apple to eat? And why would a female goat chose the male that exhibits good-looking testosterone associated courtship behavior?

These authors seem to forget about any further investigation into the biological (e.g., chemical) basis for the either the apple’s, or the male goat’s appeal. Should we also forget that someone must have once been compelled to eat an apple, and find it appealing? How would the apple’s visual appeal compel anyone to initially eat an apple? How would an animal’s visual appeal compel another animal to initially see it as a potential mate? Suddenly, due to study design, the male’s appeal is due to visually perceived courtship behavior. And I say ‘suddenly’ also because adult behavior is examined in the absence of its development.

What troubles me is that these authors know male morphology is not used by female goats for mate choice (e.g., they cite their own initial study in this regard). They also cite works that show female mammals are able to distinguish between and show preference for particular males using chemical cues alone.

Chemical cues and pheromone activity in goats are testosterone dependent. Females are able to use chemical cues alone to distinguish among high and low quality males. Thus, the courtship cues provided by males are of no concern with regard to the proximate mechanisms involved in female assessment. As it is in all species that sexually reproduce, testosterone-dependent pheromones are responsible for the male’s appeal. That’s why, in our study, we used human pheromones to enhance the appeal of a man wearing them, as demonstrated by the observed increase in women’s flirtatious behaviors, and their self-reported increased attraction.

The Sex Lives of Insects

Here’s an interesting WSJ article about a new book on the sex lives of insects. It prompted one sex researcher to ask: “Did you know that bedbug males penetrate the exoskeleton of females to fertilize them?” And to comment:  “Now that’s penetration!”

Can what is known about insects improve your sex life? The diet of the honeybee queen determines her pheromone production, and every aspect of the hive’s social behavior, including the neuroanatomy of the worker bee’s brain? Now that’s determination!

If the maternal pheromones of mammals alter the developing male brain in a sexually differentiated manner, as I have detailed, the sexual behavior of male mammals may also be conditioned to occur by olfactory/pheromonal stimuli. So, as long as we’re looking at the sex lives of insects, should we not also look at some other comparisons?

The honeybee already serves as a model organism for studying human immunity, disease resistance, allergic reaction, circadian rhythms, antibiotic resistance, development, mental health, longevity, and diseases of the X chromosome. Included among these different aspects of eusocial species survival are learning and memory as well as conditioned responses to sensory stimuli.

Is there any reason to believe that human pheromones are a less powerful influence on human behavior than are honeybee pheromones? The molecular biology of the mechanisms involved is clearly the same.

Kudos to anyone else who helps to detail the cross-species comparisons.

The Sex Lives of Insects (Part II)

The question was posed by one sex researcher: “Did you know that bedbug males penetrate the exoskeleton of females to fertilize them?” Another researcher responded that this question, and wrote that it brings up the age-old question: Which came first — the penis or the vagina? He jokingly added that the answer is pretty clear: it was the penis. This video of “penis fencing” in marine flatworms supposedly exemplifies a fact. There are …four penises flailing and not a vagina in sight: http://www.youtube.com/watch?v=5fx-YgcP8Gg

I recognize the joking nature of the above exchange, but it brings up at least three more important questions, which many sex researchers have not addressed.

1. How did the sight of a vagina become important to sexual behavior?
2. What animal model suggests the importance of visual input is greater than the importance of chemical input either in food choice or mate choice?
3. Is penis fencing in worms an indicator of the relative salience of sensory input?

In the nematode, Caenorhabditis elegans, for example, recent results suggest that even the importance of food odor is not as important to behavior as is the organism’s already ‘hard-wired’ response to the odor. “This was a surprising result because most people thought that sensory information was perceived as neutral, with the brain deciding later from the context whether it was good or bad. Some scientists said that only worms behave this way, but the same result was later obtained in mice.” [1]
1. Given this extension from a worm to a rodent, and
2. the fact that the rodent’s reproductive sexual behavior seems to be driven by its ability to acquire food, and that
3. food acquisition determines its production of social odors (as appears to be consistent across all animal species),
4. the leap to the importance of visual input (e.g., the sight of the vagina) in men seems to be a huge leap that is unsupported by at least three steps that are required to link a sensory stimulus, like a chemical stimulus, to behavior.

But wait, I think that both sex researchers were joking, and so am I, albeit only somewhat. From the perspective of molecular biology, it is clear that ligand (e.g., penis) – receptor (e.g., vagina) interaction requires the co-evolution of both. However, it does not require the evolution of vision.

How then, are sex researchers going to explain their continued focus on the importance of visually perceived physical characteristics of the opposite sex (e.g, the vagina) with regard to behavioral development in humans? The overwhelming importance of chemical stimuli in this regard is a fact of life across every species that reproduces sexually.[2]

The Sex Lives of Insects (Part II)

After the question was posed by one sex researcher: “Did you know that bedbug males penetrate the exoskeleton of females to fertilize them,” another researcher wrote that this brings up the age-old question: Which came first — the penis or the vagina? He joked that the answer is pretty clear: it was the penis. Supposedly,  this video of “penis fencing” in marine flatworms exemplifies that fact. There are …four penises flailing and not a vagina in sight.

I recognize the humorous nature of the above exchange, but it brings up at least three more important and serious  questions, which many sex researchers have not addressed.

1. How did the sight of a vagina become important to sexual behavior? (more…)

The Sex Lives of Insects: Part III

The discussion of the Sex Lives of Insects progressed and a participant commented about the surgical management of intersex infants. Gender assignment was/is often skewed towards female because surgeons find/found it “easier to make a hole than a pole.”  But he also chided that perhaps the same rules do not apply to the Intelligent Designer. Personally, I find such comments to be more than mildly offensive, but will address them from a professional perspective, which may not be well understood by those who are less familiar with molecular biology. The “rules” of the required molecular biology involve ligand-receptor binding. For example, from yeasts to mammals, genetic conservation of the ligand: gonadotropin releasing hormone (GnRH), and the diversification of its receptor (GnRHR) are part of the rules. These rules suggest it is much more difficult to make a functional hole than a functional pole. (more…)

Pheromones, LH, neurogenesis, learning, memory, behavior

Excerpts from: Environmental Impact (Research in behavioral epigenetics is seeking evidence that links experience to biochemistry to gene expression and back out again).

“…behavioral epigenetics seems to demand a different conceptual mindset in neuroscience—a focus on molecular modifications in the cell’s nucleus, rather than on interneuronal circuitry or gross anatomy…”

In my model, molecular modifications result in changes in interneuronal circuitry that are manifested in gross anatomy. Olfactory genetic neuronal hormonal behavioral reciprocity

“…it has long been obvious that some sequence of physiological events must link a human being’s experiences to one’s DNA:…”

In any mammalian model, the sequence of physiological events that link experiences to DNA begins with olfactory/phermonal input. Olfactory genetic neuronal hormonal behavioral reciprocity

“…biochemical signals in the brain … trigger molecular activity in the nuclei of neurons, shutting down some genes and increasing the activity of others. If that weren’t the case, people’s experiences could not affect their behavior.”

In any mammalian model,  the biochemical signals in the brain must trigger molecular activity in the nuclei of neurons that secrete hormones. If that were not the case, experiences could not effect hormones that affect behavior. Olfactory genetic neuronal hormonal behavioral reciprocity

My goal, reached in the early 1990′s was “… to lay out every link in the causal chain that leads from a person’s experience to a neurotransmitter, then to a particular gene, then to a specific molecular modification of protein or DNA that affects that gene, and then back out from gene products to neuronal signaling to a person’s thoughts, feelings and actions.” Olfactory genetic neuronal hormonal behavioral reciprocity

Epigenetics of Alzheimer’s disease

September 28, 2011 | 1:00 PM – 5:00 PM
Epigenetics of Alzheimer’s Disease
This symposium will review current knowledge on the contribution of epigenetic modifications in the initiation and progress of Alzheimer’s disease with the goal of advancing basic knowledge and identifying new areas for therapeutic interventions.

A recent patent application (1) and a recent journal article that present similar information (2) make it more clear that pheromones and their effect on gonadotropin releasing hormone (GnRH)-directed levels of luteinizing hormone (LH) are responsible for adult neurogenesis associated with the conditioning of behavior. Unfortunately, there is no evidence in the program information listed in the link above that this recent information will be discussed. It is even more disappointing to me that the information is not typically discussed with regard to the conditioning of behavior associated with olfactory/pheromonal input across a lifetime of experience with food odors and with social odors. Now that some people are looking at applications of what is known about pheromones in anti-aging medicine (including applications associated with neural stem cell transplants) it might benefit even those of us who are aging well to learn more about the involvement of social odors in the normal aging process.

1.         S. Weiss, E. Enwere, L. Andersen, C. Gregg, USPTO, Ed. (2011).

2.         B. W.-M. Lau, S.-Y. Yau, K.-F. So, Cell Transplant 20, 21 (2011).