Human Pheromones: Linking
Neuroendocrinology and Ethology (revisited)
International Society for Human Ethology, 2010
James V. Kohl
Clinical Laboratory Scientist
ASCP, ASCLS, AMT
JVKohl@bellsouth.net
www.pheromones.com
Adapted for presentation from:
Kohl, Atzmueller, Fink, Grammer (2001)
Human Pheromones: integrating
neuroendocrinology and ethology.
Neuroendocrinology Letters 22(5): 309-21.
and
Kohl (2007)
The Mind's Eyes: human pheromones,
neuroscience, and male sexual preferences
Journal of Psychology & Human Sexuality, 18(4): 313-369.
Concurrently published in the Handbook of the Evolution of Human Sexuality
Guest editor: Michael R. Kauth Editor: Eli Coleman. Taylor and Francis, Inc.
Support for the concept:
Kohl, Kelahan, Hoffmann (2009)
Human pheromones increase women's
observed flirtatious behaviors and ratings of
attraction
13th Annual Meeting of the Society for Behavioral
Neuroendocrinology.
East Lansing, Michigan.
Linking neuroendocrinology and ethology
Neuroendocrinology: the study of the interactions between the
nervous system and the endocrine system.
Ethology: the scientific study of animal behavior.
“The interaction between sensory input and
hormonal levels appears to be a general rule in
endocrine relationships underlying behavior.”
(LeMagnen,1982)
Sensory input effects hormones that affect
behavior.
In other words:
What are Pheromones?
Pheromones are species specific
sensory input from the social
environment that influence “…a
definite behavior or a developmental
process.”
Karlson & Luscher (1959) Pheromones': a new term for a class of
biologically active substances. Nature. 1959 Jan 3;183(4653):55-6.
[e.g., by causing changes in levels of hormones]
Levels of Biological Organization

Subatomic Particles; Atoms; Small Molecules; Macromolecules;

Molecular Assemblies; (e.g., genes) Organelle






Cell
Tissue
Organ
Organ system
Organism
Population; Species; Community; Ecosystem; Biosphere
Sexual differentiation (Naftolin, 1981)
This gene-cell-tissue-organ-organ system
pathway allows natural selection to proceed
at a pace and in directions keyed to
environmental cues, like food odors and
pheromones.
The Gonads-Hormones-Behavior (G-H-B)
model: A few genes cause gonadal
differentiation and the gonadal hormones are
responsible for the more widespread and
contemporary aspects of structural
development and function in the brain and
body.
Gene-cell-tissue-organ-organ system
In the G-H-B model, mammalian pheromones
activate gene expression in gonadotropin
releasing hormone (GnRH)-secreting nerve
cells of tissue in the medial preoptic area of
the anterior hypothalamus, which is the area of
the brain that modulates the hypothalamic GnRH
pulse.
The brain is the most important organ of any
organ system involved in behavior.
Pheromones effect hormones
and control sexual behaviors
The effect of pheromones on reproductive
hormone status is mediated by GnRH neurons.
GnRH plays an important role in the “control of
sexual behaviors” via their link to reproductive
hormone status [e.g., testosterone and
estradiol] and sexual behavior that involves
GnRH neurons. Boehm, U., Zou, Z., & Buck, L.B. (2005). Feedback
loops link odor and pheromone signaling with reproduction. Cell, 123, 683695.
Pheromones “control” definite behaviors by
causing changes in levels of hormones. Shepherd,
G. M. (2006). Behaviour: Smells, brains, and hormones. Nature, 439, 149151.
Sex differences in behavior (Naftolin, 1981)
Complex and highly variable social factors in
humans often obscure the exact mechanisms
of events [that cause sex differences in
behavior].
However, see Mak et al, (2007): Neurons in the
olfactory bulb that express GnRH receive signals
from pheromones and send projections to the
hypothalamus, which results in the release of
luteinizing hormone (LH) and follicular-stimulating
hormone (FSH) by the anterior pituitary.
Together, LH and FSH control the release of
steroid hormones, such as estrogen, that
influence sexual behavior…. (i.e., in the G-H-B model)
Nature
SEXUAL DIFFERENTIATION
Pheromones alter GnRH-modulated:
neural circuitry, odor hedonics, mood,
memory, motivation, cognitive behavioral state,
and potentiating responses to other stimuli, and link
Nature to Nurture via affective reactions
PRENATAL
PRE- and POSTNATAL
Nurture
The influence of pheromones from the same
sex or from the opposite sex on postnatal
sexual differentiation
GnRH
Nerve cell
Migration
Aging
Sexual Expression
Pheromones
From the same sex
Olfactory placode
Sexual Identity
From the opposite sex
Olfactory Bulbs
Sexual orientation
Limbic System
Extrahypothalamic GnRH
Learning and Memory
Hypothalamus
Positive
Negative
Hypothalamic
GnRH
Neuronal
feedback
Male
Female
GnRH pulse
frequency and amplitude
Tonic
Cyclic
extrapituitary effects
Pituitary
LH / FSH
NEUROTRANSMISSION
Synaptogenesis
Synaptolysis
Apoptosis
HPA
axis
Synaptogenesis
Synaptolysis
Apoptosis
HPG
axis
Adrenals
Gonads
LH
Testes
(androgenic metabolites)
Ovaries
(estrogenic metabolites)
FSH
Adrenal metabolites
(androsterone)
(etiocholanolone)
Pheromones
Luteinizing Hormone: The link between sex and the sense of smell
P
H
E
R
O
M
O
N
E
S
Sexual preference difference (1)
Hypothalamus
Medial preoptic area
of the anterior hypothalamus
MPOA/AH
MP-AHN
Pheromones, GnRH, other Hormones
and Behavior
One central neuronal (i.e., GnRH) pathway
links: noradrenergic, dopaminergic, serotoninergic, and
opiodergic pathways, as well as inhibitory neurotransmitters
like gammaaminobutyric acid and excitatory amino acids like
glutamic and aspartic acids and other brain peptides including
pineal secretions like melatonin and corticotrophinreleasing
hormone and the complex interactions among them (e.g., the
effects of hormones)…
…to functional species-specific influences,
which are linked to behavioral affect by the
same hormone-secreting cells, that
pheromones directly effect.
Pheromones and the hypothalamic
GnRH pulse
GnRH modulates the concurrent maturation of the
neuroendocrine system, the reproductive system
and the central nervous system.
GnRH is required for LH release
Increased GnRH pulse frequency favors LH release.
The opposite sex pheromones of other mammals
cause LH release.
Axillary pheromones of men cause LH and mood
change in women
Prepubertal conditioning
"There is now ample evidence that GnRH is
secreted episodically in the prepubertal
child long before physical signs of puberty
appear (Jakacki et al., 1982). The onset of puberty
therefore appears to be associated with an
amplification of pulsatile gonadotropin
secretion.”
Hopwood, N.J., Kelch, R.P., Hale, P.M., Mendes, T.M., Foster, C.M., & Beitins.
I.Z. (1990) The onset of puberty: biological and environmental factors. In:
Bancroft, J, & Reinisch, J.M. (eds.) Adolescence and Puberty. (pages
29-49) New York: Oxford University Press.
The neuroendocrinology of
diverse sexual preferences
Unconditioned stimulus (UCS): Pheromones
Conditioned stimulus (CS): visual, auditory,
tactile, gustatory—combined?
The CS (e.g., visual input), gains behavioral
significance after being paired with a
biologically active UCS (e.g., pheromones).
Odors/pheromones are the proximate cause
Hormone-driven preferences are their effect.
Affective primacy
1.Positive and negative affective reactions can
be evoked with minimal stimulus input and
virtually no cognitive processing.
2.Affect dominates social interaction and it is
the major currency in social interactions
3.Affective reactions can occur without
extensive perceptual and cognitive encoding.
They are made with greater confidence than
cognitive judgments, and can be made
sooner.
Affective primacy is
Olfactory primacy
Olfactory input from the social environment fits
the assertions of affective primacy.
For example, chemical cues allow humans to
select for, and to mate for, traits of
reproductive fitness that cannot be assessed
simply from visual cues.
The affect of pheromones on our emotions
is linked to the effect of pheromones on the
hormones of the hypothalamic-pituitarygonadal axis – an unconscious affect.
Affect, olfactory primacy, and other
sensory input
Affect is conditioned in the presence of other sensory input.
Mammalian neuroanatomical pathways link vision and
olfaction. Cooper et al. (1994)
Conditioning the response to
visual stimuli (in rats)
Social-environmental odor cues, which males learn to
visually associate with sexual activity, can be used to
condition LH release.
After minimal conditioning, an arbitrary odor ultimately will
elicit a male LH response, even in the absence of odor
previously associated with a female.
Regardless of whatever other sensory input (e.g., visual
input) is involved, the functional significance of the
conditioned change in LH secretion lies principally in the
unequivocal demonstration that olfactory cues can
activate the male hypothalamic-pituitary-gonadal axis in
a way that mimics, in every respect, the activation
achieved by exposure to a female. Graham & Desjardins (1980)
High Estrogen/Androgen ratios,
physical features…
Feminine features: small jaw, full lips, large
breasts, narrow waist, shorter, higher vocal
pitch, light complexion, etc.
…AND THE PHEROMONES OF WOMEN.
Low Estrogen/Androgen ratios,
physical features…
Masculine features: growth of the jaw, brow
ridges, center of the face from the brow to
the bottom of the nose, more facial hair,
taller, darker, more muscular, etc.
…AND THE PHEROMONES OF MEN.
Hormone-dependent features
Used with permission from Victor Johnson
Poster session:
J.V. Kohl; L.C. Kelahan; H. Hoffmann
HUMAN PHEROMONES INCREASE WOMEN’S
OBSERVED FLIRTATIOUS BEHAVIORS AND RATINGS OF
ATTRACTION.
Conclusions: The known effect of androstenol on luteinizing
hormone in women and what appears to be an associated
behavioral affect of androsterone meet criteria that
characterize human pheromones.
Kelahan-testing and results; Hoffmann-professorship; Kohl-study design
Terms of Endeerment
“[Cindy] ... had gone alone to a portable commode
hidden in a thicket to change her tampon,
unaware that a young stag was nearby...
Smelling her [natural] secretions, [the male deer]
became sexually aroused. He bounded through
the trees and knocked Cindy to the ground.
Then while prancing up and down with his
forefoot on her shoulder, the sexually excited
deer sprinkled her with semen."
Gibbons, D.L. (1989) Unusual case: Sex in the woods. Medical Aspects of Human
Sexuality, 23, 10(Oct), 63.
Sexual Odors / Food Odors
“It is important to remember that the
animal perceives erotic odors in a
manner analogous to his perception
of food odors.”
Bloch, I. (1933) Odoratus Sexualis: A Scientific and Literary Study of
Sexual Scents and Erotic Perfumes. New York: American Anthropol.
Soc.