Pheromone Friday

Pheromones, emitted chemicals that elicit a social response in members of the same species, have been most widely studied in insects as a mode of communication. In the insect world, pheromones can signal alarm, mark trails, control worker bee behavior, and elicit sexual behavior.

Sex pheromones are the chemicals that come to mind in popular lore. Do human beings secrete substances that are likely to attract potential mates? Unscrupulous players in the fragrance industry would like you to believe that's the case. Unable to attract women (or men)? There's a difference between marketing an intoxicating and sensual fragrance that's pleasing to the nose and snake oil such as:

Amazon even cautions prospective customers about SexyLife.





{BTW, humans lack a functional vomeronasal organ, the part of the accessory olfactory system that detects pheromones / chemosignals / non-volatile molecules (Petrulis, 2013).}


Don't we already know that human pheromones are a crock?

It depends on how you define pheromone, some would say.¹ “In mammals [rodents], few definitive cases have been identified in which single pheromone compounds evoke robust sexual behaviours, which might reflect an important contribution of signature mixtures in sexual communication” (Gomez-Diaz & Benton 2013, The joy of sex pheromones). In rodents, reproductive responses to “odor blends” or chemosignals are heavily modulated by experience, as opposed to the instinctive and fixed behaviors elicited by pheromones in insects. The evidence supporting the existence of mammalian pheromones is so weak that Richard Doty has called it The Great Pheromone Myth.

If rats don't have “pheromones” per se, why look for them in humans? Tristram Wyatt, who believes that human pheromones probably exist, wrote a paper called The search for human pheromones: the lost decades. He criticized the literature on four androgen-related steroids (androstenone, androstenol, androstadienone and estratetraenol), saying it suffers from publication bias, small sample sizes, lack of replication, and commercial conflicts of interest. There is no bioassay-based evidence that these molecules are human pheromones, yet “the attraction of studies on androstadienone (AND) and/or estratetraenol (EST) seems unstoppable” (Wyatt, 2015).

{Curiously, the SexyLife ad accurately lists the putative male pheromones, although their depicted functions are pure fantasy.}

Unstoppable it is. Supporters of human pheromones have recently published positive results on male sexual cognition, male dominance perception, cross-cultural chemosignaling of emotions, and sex differences in the main olfactory system.²


Olfactory Attraction

On the other hand, a null finding from 2017 drew a lot of attention from popular media outlets and Science magazine, where the senior author stated: “I’ve convinced myself that AND and EST are not worth pursuing.” In that study, AND & EST had no effect on the participants' attractiveness ratings for photographs of opposite-sex faces (Hare et al., 2017).

The evolutionary basis of Smell Dating was given a cold shower by studies showing that the fresh (and odorless) armpit sweat of men and women, when incubated in vitro with bacteria that produce body odor, were rated identically on pleasantness and intensity (reviewed in Doty, 2014). Meanwhile, the day-old smelly armpit sweat of men was rated as equally unpleasant by men and women.³ Likewise, pleasantness and intensity ratings for female armpit sweat did not differ between men and women. This doesn't bode well for heterosexual dating...

Odors and fragrances are an important part of attraction, of course, but don't call them pheromones.


Footnotes

¹ There is an accepted definition for "pheromone".

² Since humans don't have an accessory olfactory system with its fun vomeronasal organ, the main olfactory system would have to do the pheromone-detecting work.

³ This could be due to larger apocrine glands, hairy armpits, and more carnivorous diets in men (Doty, 2014).


Further Reading

Scientific post in favor of human pheromones:

• On the Existence of Human Pheromones

“Whether one chooses to believe in the existence of human pheromones or not, steroids clearly serve an essential olfactory signaling function that impacts broadly ranging aspects of the human condition from gender perception to social behavior to dietary choices.”

PET studies on AND, EST, and sexual orientation:

• Sweat, Urine, and Sexual Orientation
• The PNAS Word

• Review of PET studies on AND & EST

References

Doty RL. (2014). Human Pheromones: Do They Exist? In: Mucignat-Caretta C, editor. Neurobiology of Chemical Communication. Boca Raton (FL): CRC Press/Taylor & Francis; Chapter 19.

Gomez-Diaz C, Benton R. (2013). The joy of sex pheromones. EMBO Rep. 14(10): 874-83.

Hare RM, Schlatter S, Rhodes G, Simmons LW. (2017). Putative sex-specific humanpheromones do not affect gender perception, attractiveness ratings orunfaithfulness judgements of opposite sex faces. R Soc Open Sci. 4(3):160831.

Petrulis A. (2013). Chemosignals, hormones and mammalian reproduction. Horm Behav. 63(5): 723-41.

Wyatt TD. (2015). The search for human pheromones: the lost decades and the necessity of returning to first principles. Proc Biol Sci. 282(1804):20142994.

Olfactory Attraction and Smell Dating

Smell Dating, an interactive exhibit by Tega Brain and Sam Lavigne

at The Glass Room.

A conceptual art installation, an extended olfactory performance piece, an elaborate participatory project, or an actual smell-based dating service? Smell Dating is all of these and more!

How it works

1. We send you a t-shirt
2. You wear the shirt for three days and three nights without deodorant.
3. You return the shirt to us in a prepaid envelope.
4. We send you swatches of t-shirts worn by a selection of other individuals.
5. You smell the samples and tell us who you like.
6. If someone whose smell you like likes the smell of you too, we'll facilitate an exchange of contact information.
7. The rest is up to you.

My initial view of the project was based a recent showing of the interactive exhibit, where the participants could sniff small swatches of cloth, rate the unknown wearer's attractiveness (UNATTRACTIVE — NEUTRAL — ATTRACTIVE), learn how others voted, and see basic background information about the wearer (e.g., 30 year old female bisexual pescatarian). The first two I sniffed were odorless, but then there was #8...

The art installation is part of Useless Press, “a publishing collective that creates eclectic Internet things.” I assumed it was an elaborate joke, not an actual matchmaking service, but the artists must have had a grant to implement the idea in real life.

Smell Dating @ Shanghai

In Shanghai, people signed up over a two week period and paid ¥100 to become a “member.”

Smell Dating @ Shanghai [culminated] in the Sweat Lab, a participatory installation event... Visitors are invited to volunteer in the Smell Dating Sweat Lab and intimately experience the smells of strangers. During this event we will prepare the smell samples from our members t-shirts. Shirts will be meticulously cut up and batched to be sent back to Smell Dating members.

Smell Dating premiered in New York in March 2016 and received extensive press coverage, most of which took it seriously. Young female writers at The Guardian, Business Insider, Time, Racked, and a gay man at HuffPo tried out the service. The Buzzfeed reporter realized, “Yes, this is mostly a stunt-y gag” but also touched on the science behind smell and attraction. The health reporter at Time wrote about the underlying science in detail (e.g., major histocompatibility complex) and interviewed smell scientists, including Dr. Noam Sobel (founder of SmellSpace.com), Dr. Richard Doty (author of The Great Pheromone Myth), and Dr. Gary Beauchamp (Emeritus Director of the Monell Chemical Senses Center).

The creators of Smell Dating (Tega Brain and Sam Levine) consulted with olfactory scientists and provided an extensive reading list on the web site.

Most everyone agrees that odors evoke emotion, and the sense of smell has a unique relationship to autobiographical memory. But, as Richard Doty asks, do human pheromones exist?

While it is apparent that, like music and lighting, odors and fragrances can alter mood states and physiological arousal, is there evidence that unique agents exist, namely pheromones, which specifically alter such states?

It turns out that scientific opinion on this matter is decidedly mixed, even polarizing, as I'll discuss in the next post.


Reference

Doty RL. (2014). Human Pheromones: Do They Exist? In: Mucignat-Caretta C, editor. Neurobiology of Chemical Communication. Boca Raton (FL): CRC Press/Taylor & Francis; Chapter 19.




Smell Dating from Tega Brain.

The Neural Correlates of Channeling the Dead

November 2nd is the Day of the Dead, a Mexican holiday to honor the memory of lost loved ones. If you subscribe to certain paranormal belief systems, the ability to communicate with the dearly departed is possible via séance, which is conducted by a Medium who channels the spirit of the dead.

Since I do not subscribe to a paranormal belief system, I do not think it's possible to communicate with my dead wife. Nor am I especially knowledgeable about the differences between mediumship vs. channeling:

Mediumship is mostly about receiving and interpreting messages from other worlds.

Mediums often deliver messages from loved ones and spirit guides during readings.
. . .

...channeling is often about receiving messages from other types of entities, such as nature spirits, spirit guides, or even angels.

In short, Channels can communicate with a broader class of non-corporeal entities, for instance Mahatma Ghandi or Cleopatra (not only the dead relatives of paying clients).

What seems to be uncontroversial, however, is that Channels who enter into a trance state to convey the wisdom of Gandhi may experience an altered or “expanded” state of consciousness (regardless of the veracity of their communications). This permuted state of arousal should be manifest in the electroencephalogram (EEG) as an alteration in spectral power across the range of frequency bands (e.g., theta, alpha, beta etc.) that have been associated with different states of consciousness.

A group of researchers at the Institute of Noetic Sciences adopted this view in a study of persons who claimed the ability to channel (Wahbeh et al., 2019). The participants (n=13; 11 ♀, 2 ♂) were on average 57 year old white women of upper middle class socioeconomic status, representative of the study site in Marin County, California. The authors screened 155 individuals to arrive at their final sample size.¹ Among the stringent inclusion criteria was the designation of being a Channel who directly and actively conveys the communications of a discarnate entity or spirit (rather than being a passive relay).² The participants were free of major psychiatric disorders, including psychosis and dissociation (according to self-report). Oh, and they had the ability to remain still during the channeling episodes, which was advantageous for the physiological measurements.

The participants alternated between channeling and no-channeling in 5 minute blocks while EEG and peripheral physiological signals (skin conductance, heart rate, respiration, temperature) were recorded. At the end of each counterbalanced session (run on separate days), voice recordings were obtained while the participants read stories.

Contrary to the authors' predictions, they found no significant differences between the channeling and no-channeling conditions for any of the physiological measures, nor for the EEG analyzed in standard frequency bands (theta 3–7 Hz; alpha 8–12 Hz; beta 13–20 Hz and low gamma 21–40 Hz) across 64 electrodes. I'll note here that the data acquisition and analysis methods were top-notch. The senior author (Arnaud Delorme) developed the widely used EEGLAB toolbox for data analysis, which was described in one of the most highly cited articles in neuroscience.³

Modest differences in voice parameters were observed: the channeled readings were softer in volume and slower in pace. The authors acknowledged that the participants could have impersonated an alternate voice during the channeling segments, whether consciously or unconsciously.

So does this mean that channeling is a sham? The authors don't think so. Instead, they recommended further investigation: “future studies should include other measures such as EEG connectivity analyses, fMRI and biomarkers.”


Footnotes

¹ This is a rather esoteric population, so I won't fault the researchers for having a small sample size.

² “The channeler goes into a trance state at will (the depth of the trance may vary) and the disincarnate entity/spirit uses the channeler’s body with permission to communicate directly through the channeler's voice, body movements, etc. (rather than the channeler receiving information mentally or otherwise and then relaying what is being received).”

³ I was rather critical of a previous study by this research group, which was ultimately retracted from Frontiers in Neuroscience. See Scientific Study Shows Mediums Are Wrong 46.2% of the Time.


Reference

Wahbeh H, Cannard C, Okonsky J, Delorme A. (2019). A physiological examination of perceived incorporation during trance. F1000Research 8:67.

Bev Tull, the fake medium on Bad Girls.