Perfuming the Mind




Perfuming the Mind: The Biological Logic of Physical Attraction


By James V. Kohl



People tend to think of "seeing" or "observing" directly with their senses, as if what we see, hear, touch, taste, or smell directly determines our overall impression of the world around us. Few people think about unconscious affect, which by its nature does not require any thought.


The influence of the pheromones from one person on hormone levels in another person is an unconscious affect. The unconscious affect of pheromones on hormones incorporates biological logic that explains how we interpret what we "see" in others.[1]      


All mammals use pheromones — chemicals that signal reproductive fitness and ensure proper timing for sexual behavior and mate choice by changing hormone levels. The sense of smell alone is sufficient to respond to mammalian pheromones, and the hormone response is not consciously processed.[2]


When it comes to the development of sexual behavior, unconscious affect (e.g., on hormones) is, ultimately, a more powerful force than conscious processing or cognitive function. The powerful force of unconscious affect is obvious in other mammals; their sexual behavior does not require any conscious processing.


People are the only mammals who incorporate conscious processing into what they think when they see another person.[3] Other mammals do not think about the visual appeal of a potential mate; their sexual behavior is biologically directed by the unconscious affect of pheromones on hormone levels.[4] Despite what most people think, human sexual behavior also is directed by the unconscious affect of pheromones on hormone levels.


Pheromone production and distribution are dependent on hormone levels like estrogen (E) and testosterone (T), which make the natural body odor, scent, or pheromones, of men and women different. When we are exposed to the pheromones of another person, we respond with changes in E and T (and other hormones) that influence our sexual behavior. The pheromone-induced changes in E and T (as well as in other hormone levels) determine what we find physically appealing when we look at another person via the developmental effects of E and T on the neuronal pathways (i.e., wiring) of the brain.[5]


What we find physically appealing when we look at another person is how sex differences in hormones like E and T have shaped the physical characteristics that are different in the sexes (e.g., facial characteristics, waist-to-hip ratio, pendulous breast development). But there is no direct link from what we see to sex differences in sensory processing, hormonal changes, or any sex difference that would allow men and women to respond differently when they see another man or woman.


The unconscious affect of pheromones on hormones directly links olfactory input and changes in our hormone levels to what we see when — at the same time —  we are exposed to the pheromones of other people. At best, the link from the visual appeal of others to changes in our behavior is a conditioned response to pheromones.[6] But the bottom line is: olfactory conditioning may cause us to behave, sexually, like other mammals. Once visual appeal is conditioned to pheromones, olfactory input is no longer required. We will respond to what we see, just as if we saw it while experiencing the unconscious affect of pheromones.


Other mammals don't look for a good-looking mate. Males sniff out females that use pheromones to advertise fertility; females sniff out males that use pheromones to advertise reproductive fitness. Biologically based mammalian models of sexual behavior rely on basic sex differences: a sex difference in the signal being sent, and a sex difference in the unconscious affect of signal processing.  If males and females did not respond differently to sex differences in pheromones from other males and females, there would be no biological basis for choosing an opposite sex mate.[7]


Any influence that disrupts the development of sex differences in the brain before we are born, also disrupts the development of sex differences in the olfactory system. A mother’s psychological stress, or her exposure to environmental toxins, or changes in her immune system status will also influence sex differences in the sense of smell. Any genetic difference that results in incomplete sexual differentiation of the olfactory system can result in a sex-atypical response to pheromones.[8]


Components of natural body odor (e.g., scent) vary with genetic sex and with sexual orientation. Heterosexual males and females as well as homosexual males and females produce different scents. Heterosexuals prefer the scent of the opposite sex; homosexuals prefer the scent of the same sex. These preferences begin to develop at birth due to the unconscious affect of pheromones on hormones and behavior.


Once a child is born, sex differences in the sense of smell determine how the child responds to pheromones. If the child is genetically predisposed to respond in a typical manner to pheromones of the opposite sex, that child will develop a preference for the pheromones of the opposite sex. If the child does not respond in a typical manner to the pheromones of the opposite sex, that child will be predisposed to develop a preference for the pheromones of the same sex.


All mammalian sexual behavior, including human sexual behavior is driven by pheromones. Since only humans make conscious associations (e.g., think), men and women are likely to think that their sexual behavior is driven by visually perceived physical attraction. This erroneous thinking defies biological logic, and consistently fails to offer an explanation for many aspects of human sexual behavior (e.g., paraphilias, and homosexuality).[9]




During the week ending September 10, 2005 five of six news articles defy this biological logic by examining aspects of physical attraction from a visual perspective. Here is a brief review of the six articles, with my comments on how they defy or incorporate biological logic.


1. Baby study suggests beauty is not in the eye of the beholder. By Rachelle Money[10]

Newborn babies spend 60-65% (of the time allotted) looking at attractive faces, compared to unattractive faces. Babies are born with a genetic predisposition that causes them to favor pretty faces rather than unattractive ones. The perception of beauty is genetically determined rather than socially constructed.


Defying biological logic

No model suggests that the infants of any mammalian species are born with a genetic predisposition to favor pretty faces. Avian models of attractive adult plumage are, literally, for the birds; we are mammals. It is unlikely that humans managed to diverge from the biological basis of mammalian physical attraction ( i.e., pheromones and olfaction). Biology favors an olfactory explanation. Newborn infants have a fully developed sense of smell. This means newborns can distinguish between very slight differences in scent signatures. They respond to the pheromones of their mother instantly and learn to recognize her scent within 24 hours of birth. Because there is no biological basis for their direct response to visual input, it appears that newborn infants respond to olfactory cues that are associated with beauty. That would explain why they spend more time looking at attractive faces: the pheromones of attractive people elicit a more powerful unconscious affect.


2. Ah, sweet mysteries of science. By David P. Barash [11]

Women conceal ovulation to keep men around for more than the brief time it takes to conceive, or perhaps to ensure another woman doesn't interfere with the selection process.


Defying biological logic

The concept of concealed ovulation could be born only from illogical human thought processes. This concept should have been abandoned when a study based on properly timed mammalian reproductive sexual behavior showed that men prefer the scent of ovulatory phase women. An earlier study showed that men exhibit the typical male response to the pheromones of ovulatory phase women: an increase in T. Nearly 30 years ago, forward thinking researchers wrote that a form of communication exists between men and women by which she informs him that she is ovulating, and he responds—as does the dominant male rhesus monkey — with a testosterone increase, that facilitates properly timed reproductive sexual behavior.[12]  Thirty years ago, researchers may not have known exactly what form of communication they had revealed, but at least they recognized that the cue wasn't visual.


Who cares whether women exhibit visual cues that they are ovulating? Men can detect the olfactory cues. Ovulation is not concealed.




3. Child murders not a modern phenomenon. By Bob Campbell ([13]

More step-dads and boyfriends kill children than do biological fathers. Many mammalian males exhibit this behavior as a reproductive strategy. Why help the child of another male survive?


Incorporating biological logic

Male mammals sniff out genetic differences in infants, and if the male detects olfactory cues that tell him the infant is not his offspring, he kills it. As hideous as this behavior might appear to be, it is biologically driven. The odor cues of another male’s male child elicit chemical changes in the brain that lead to murderous behavior.


The odor cues of another male’s female child will, with her sexual maturity, elicit a sexual response. This olfactory approach offers the best explanation for step-father/daughter incest.


4.Cowboys in Love . . . With Each Other. By Karen Durbin[14]

A movie review examines male homosexuality: “Cowboys in Love…With each other.”


Incorporating biological logic

How does one cowboy develop physical attraction for another cowboy? Does he wake up one day and decide that the visual appeal of the other cowboy is so arousing that he must have sexual relations with him? Proponents of non-mammalian approaches to physical attraction have some explaining to do when it comes to same-sex attraction. It’s not biologically feasible to explain heterosexuality with one approach, and take a different approach when explaining homosexuality.


Mammalian models of heterosexuality and homosexuality incorporate the olfactory-pheromonal approach. Homosexuals respond hormonally and behaviorally to the pheromones of the same sex. Human studies suggest that the preference for same sex odors is developed based upon genetic predispositions that alter the brain’s response to pheromones. 


5. Men, women and Darwin. By Julia M. Klein.[15]

In speed-dating scenarios, both men and women regard physical attraction as most important, but perhaps for different reasons.


Defying biological logic

The appeal of physically attractive features develops as males and females mature. Preadolescent males and females do not find sex differences to be important enough to form the basis for a lasting physical relationship. We already know that even when men and women say that physical attraction is most important, if a potential mate doesn’t smell right, there will be no relationship. However, some people don’t realize how much the scent of others influences their mate choice as adults.


Testosterone is responsible for men being taller, with darker complexions, and for their masculine facial features (e.g., a more pronounced jaw). Testosterone is also responsible for male pheromone production; higher testosterone means a more masculine scent signature. Tall, dark, and handsome is merely a visual description of a masculine scent signature.


Estrogen makes the physical features of women vary from those of men, and also makes the scent of a woman different than the scent of a man. Estrogen is responsible for establishing the foundation for body fat distribution that makes the most attractive waist-to-hip ratio (WHR) approximately 0.7 in women, compared to approximately 1.0 in men. A woman with a 0.7 WHR smells better to a man, just as a woman who is in her ovulatory phase smells best to a man — because her hormone levels reflect and signal increased reproductive fitness.




6. Passion and the Prisoner By Daphne Merkin.[16]

Women are attracted to the scent of demonic males; “Such is the unreasonable pull of pheromones…”



Incorporating biological logic

Testosterone masculinizes the facial features and the scent signature of men. In an experiment that changed facial characteristics across a continuum from the most feminine to the most masculine, the most masculine face was described as demonic. The association is clear; women are attracted to the scent of testosterone-charged males. In other mammals higher testosterone levels correlate well with reproductive fitness.


"Women have to know a whole lot more about a man before going to bed with him. They have to smell him.."[17]


Only one of the articles above mentions pheromones, and their role is typically ignored in the mass media. What we continue to read, or are led to believe, is that many aspects of human sexual behavior are relatively unexplained when compared to the biologically based sexual behavior of other mammals. One reason aspects of human sexuality are relatively unexplained is that so many people refuse to incorporate mammalian biology—or any biology. Without some model on which to base our interpretation of study findings, the science of human attraction is a free-for-all.


Study after study can report findings that indicate physical attraction is based on visual input, and most people will be none the wiser. Indirect evidence that we are primarily visual creatures equates with blind belief. We must ignore the biological fact that, as mammals, we are not primarily visual creatures. And we ignore biology at our own peril. If we don’t understand the biological basis for our behavior, how will we ever learn either to accept it or to change it?


Qazi Rahman, who is co-author of the recently released book: Born Gay: the Psychobiology of Sex Orientation, reportedly dismisses "95 per cent of psychology as rubbish." The psychoanalytical idea that distant fathers or overbearing mothers sabotage their sons' sexual development is not borne out by evidence.[18]


Dr. Rahman was among a select group of researchers who attended the August 2005 International Behavioral Development Symposium: Biological Basis of Sexual Orientation, Gender Identity, and Sex-Typical Behavior. Many of the researchers who attended have similar sentiments when it comes to psychological explanations of human sexual behavior. Until there is more focus on mammalian biology and unconscious affect, many people will continue to have misconceptions about human sexuality based upon an ongoing stream of misinformation.<





Kohl, JV (2005) "Human Pheromones, Neuroscience, and Male Homosexual Orientation"; International Behavioral Development Symposium. Minot, ND, Aug 3-6. Entelechy: Mind & Culture; issue No. 6.


Kohl, JV and Francoeur, RT (2002; 1995) The Scent of Eros: Mysteries of Odor in Human Sexuality.


Kohl JV, Atzmueller M, Fink B, & Grammer K (2001) Human Pheromones: Integrating Neuroendocrinology and Ethology. Neuroendocrinology Letters: 22(5) 309-321.


Diamond M, Binstock T, & Kohl JV (1996) From fertilization to adult sexual behavior: Nonhormonal Influences on sexual behavior. Hormones and Behavior. 30: 333-353.





[1] The chemical components of natural human body odor  (e.g., pheromones) activate the medial preoptic area of the anterior hypothalamus (MPOA/AH), which varies with genetic sex and with male sexual orientation either by size or neuronal density.  During development, the MPOA/AH generates the hypothalamic gonadotropin releasing hormone (GnRH) pulse, which modulates the concurrent maturation of the reproductive system, the neuroendocrine system and the central nervous system.

[2] Human pheromones elicit the typical mammalian GnRH-directed luteinizing hormone (LH) response. This hormone response makes debate over the presence and function of the human vomeronasal organ (VNO) irrelevant.

[3] It is only via a gene-cell-tissue-organ-organ system pathway that sensory input from our social environment can directly influence behavior. The brain must be part of any organ system that responds to sensory input and affects behavior.

[4] Beginning with gene activation in nerve cells of brain tissue that secrete GnRH, there is a direct link from chemical signals in our social environment (pheromones) to developmental changes in hormone levels e.g., luteinizing hormone (LH), estrogen (E), and  testosterone (T), to developmental changes in our brain; and to developmental changes in behavior.

[5] Throughout life, E and T encourage, inhibit, or eliminate the development of nerve cells and connections between nerve cells in the brain.

[6] Pheromones influence hormone levels, and the hormone-dependent behavioral changes are consciously associated with visual input.

[7] Sex differences in behavior can develop only when there are sex differences in signals and sex differences in signal processing.  Males and females produce different pheromones. The olfactory system of males and females develops sex differences before birth. From the time we are born, these sex differences dictate that the response to pheromones in males and females is different. Pheromones cause a GnRH-directed change in LH levels. The typical LH increase occurs with exposure to the opposite sex. The LH increase precedes pheromone-induced changes in E and T levels.

[8] Before birth, genes and environmental exposure influence sex differences in the sense of smell by influencing hypothalamic GnRH pulsatility. A single genetic difference is all that stands between someone who is born with the ability to smell, and someone who is anosmic (can’t smell anything; doesn’t respond to pheromones).

[9] There is no mammalian model of visually perceived physical attraction. In contrast, sexually dimorphic MPOA/AH size or neuronal density allows a sexually dimorphic unconscious affect of pheromones on GnRH, and thus on the entire hypothalamic-pituitary-gonadal and hypothalamic-pituitary-adrenal axes, both of which are essential components of mammalian sexual behavior, including human sexual behavior, which includes sexual orientation.


[12] Persky, H., Lief, H.I., O'Brien, C.P., Straus, D., & Miller, W. (1977) Reproductive hormone levels and sexual behavior of young couples during the menstrual cycle. In: Genne, R., & Wheeler, C.C. (eds.) Progress in Sexology: Selected Papers from the Proceedings of the 1976 International Congress of Sexology. (pages 293‑310) New York: Plenum Press.


[17] Heimel, C. (1995) The genetics of nose jobs. Playboy, 42 (Jan), 1, 36.




James V. Kohl is considered by many to be the foremost internationally known authority on human pheromones. He continues to present to, and publish for, diverse scientific and lay audiences as new information becomes available. Kohl's 1995 book, Scent of Eros was released in 2002 as an updated paperback edition.
Kohl has worked as a clinical laboratory scientist since 1974, and he has devoted more than sixteen years to researching the relationship between odors and human sexual behavior. He is certified with the National Credentialing Agency for Laboratory Personnel, American Society for Clinical Laboratory Science, and the American Medical Technologists. He is a member of the Society for the Scientific Study of Sexuality, the Association for Chemoreception Sciences, Human Behavior and Evolution Society, Mensa, and the Society for Behavioral Neuroendocrinology and the Across-Species Comparisons and Psychopathology Society (a branch of the Psychotherapy Section of the World Psychiatric Association). Kohl developed his public speaking skills as a former member of Toastmasters International. He began presenting his findings to the scientific community in 1992 and continues to do so, while constantly monitoring the scientific presses for new information that is relevant to the concept of human pheromones. He was invited to participate during the prestigious International Behavioral Development Symposium: Biological Basis of Sexual Orientation and Sex-Typical Behavior (1995), which is reported here: "... 89 scientists participated... [T]he conference was... the first to assemble virtually all the top researchers in the field."  Kohl returned to participate in the equally prestigious second International Behavioral Development Symposium held in 2000, and will return for the third symposium in 2005. His 2001 peer-reviewed journal publication (with distinguished colleagues from Vienna) detailed the role of pheromones in heterosexual attraction, and received The Zdenek Klein award (diploma and medal) for the best paper linking neuroendocrinology and ethology.


To read "Human Pheromones, Neuroscience, and Male Homosexual Orientation," also by James V. Kohl, click here.




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