Pheromones and behaviour 2.2 Biological

Pheromone

A chemical substance produced and released into the environment by an animal, affecting the behaviour/physiology of others of its own species

Pheromone role

Significant role of signaling between members of the same species among animals

How are pheromones detected?

Vomeronasal organ (VNO)

Where is the vomeronasal organ located?

Anterior nasal cavity

What does the vomeronasal organ connect to?

Special region in the brain called the accessory olfactory bulb

Two types of pheromones

Primer pheromones

Signaling pheromones

Primer pheromones

Slow, long-term physiological changes (e.g. hormonal effects)

Signaling pheromones

Rapid behaviour effects (e.g. mating)

Major Histocompatibility Complex (MHC)

A group of genes that play an important role in the immune system

Wedekind (1995) Aim

Determine whether an individual's major histocompatibility complex (MHC) would affect mate choice.

Wedekind (1995) Participants

49 female and 44 male university students

Participants were tested to identify their MHC genes, and a wide variance of MHC was included in the sample.

Wedekind (1995) Procedure

Men were asked to wear a t-shirt for two nights and keep it in an open plastic bag during the day. They were given perfume-free detergent to wash clothes and bedclothes as well as perfume-free soap for showering. They were asked to avoid activities that would produce unnatural odours.

Two days later, the women ranked the smell of 7 t-shirts after the beginning of menstruation.

3/7 boxes contained t-shirts from men with similar MHCs to the woman's own, 3/7 contained dissimilar ones, and one contained an unworn t-shirt as a control.

Women individually scored the t-shirts for intensity and pleasantness/sexiness.

Wedekind (1995) Findings

Women scored male body odors as more pleasant when they differed from their own MHC. This difference in odor assessment was reversed when the women were taking oral contraceptives.

Wedekind (1995) Conclusion

MHC may influence human mate choices, and we are more attracted to dissimilar genes.

Wedekind (1995) Evolutionary argument

The dissimilar MHC genes mean that offspring created will have a larger variety in genes, resulting in a strong immune system and therefore a greater chance of survival