Pheremones Flashcards
Define pheremones
A chemical substance that is usually produced by an animal or insect that serves especially as a stimulus to other individuals of the same species for one or more behavioural response.
- existence in humans is still uncertain.
- The detection of pheromones in mammals usually relies on a structure called the VNO in the nose that transmit signals via the accessory olfactory bulb to the hypothalamus in the brain.
- VNO and olfactory bulb has not been shown to exist in humans, though both exist in the foetus up to about 18 weeks.
- no chemical has been definitely identified as a human pheromone, but the evidence for chemicals in tears, breast milk and sweat that act as if they were pheromones, to attract humans to each other, is growing.
What is the pheromone and behaviour involved in the Wedekind study (1995)
[Theory/hormone we release/natural selection]
There are theories that one of the potential role of pheromones in human behaviour is responsible for mate selection.
MHC - group of genes that play an important role in the immune system
The more diverse the set of genes for the MHC is in the parent, the stronger it is in their offspring, which makes it very favourable to choose a mate with a different MHC combination for natural selection.
Aim of Wedekind
to determine whether one’s MHC would affect mate choice.
Method of Wedekind
49 female and 44 male students from a University of Bern. There was wide variance of MHC. It was noted if the women were taking oral contraceptives. The students from different courses probably did not know each other
men wears a T-shirt for two nights and to keep the T-shirt in an open plastic bag during the day. They were asked to refrain from actions and products that could affect their natural scent (tobacco/perfume etc)
women then rank the smell of 7 t-shirts. The women were tested in the second week after the beginning of menstruation, as women appear to be most odour-sensitive at this time. They prepared themselves for the experiment by using a nose spray for the 14 days before the experiment to support regeneration of the nasal mucous membrane if necessary – as well as a preventive measure against colds or flu.
3/7 boxes contained T-shirts from men with MHC similar; three contained T-shirts from MHC dissimilar men;
1/7 contained an unworn T-shirt as a control.
Alone, they scored the odours of the t-shirt for intensity (0-10) and for pleasantness and sexiness (range 0 -10, 5 = neutral).
Findings of Wedekind
Women scored male body odours as more pleasant when they differed from their own MHC than when they were more similar. This difference in odour assessment was reversed when the women rating the odours were taking oral contraceptives.
Conclusion of Wedekind
This suggests that the MHC may influence human mate choice.
What is the pheromone and behaviour involved in the Zhou study (2014)
[Steroid/Function/Behaviour]
AND and EST are human steroids. AND is present in male semen and sweat. It heightens sympathetic arousal, alters levels of cortisol, and promotes positive mood state in females. It is also found to activate the hypothalamus in heterosexual females or homosexual male.
EST is the female equivalent of AND.
Aim of Zhou
To investigate the chemosensory communication of gender in a sex specific manner, through the testing of male and female reactions to the two human steroids AND (signalling maleness) and EST (signalling femaleness)
Method of Zhou
96 participants (24 heterosexual women, 24 heterosexual men, 24 gay men, 24 lesbian women).
1) Cloves mixed with AND (found in male sweat and semen)
2) Cloves mixed with EST (found in female urine)
3) Regular cloves (control group)
In identical small jars from which participant inhaled during the experiment. The participants were asked to watch and identify the gender of the figure walking, under each condition:
Findings of Zhou
Smelling AND biased heterosexual females and homosexual males towards perceiving the walkers as more masculine. Smelling EST biased heterosexual males towards perceiving the walkers as more feminine.
Conclusion of Zhou
This information strongly supports them as human sex pheromones
