New Scientist has this interesting article on human pheromones. It’s amazing to find that we are unconsciously able to detect information and messages about each other.

What are pheromones?
Actually, there is quite a lot of debate about that. Basically, pheromones are chemical messages emitted by animals that trigger responses in receivers.

For example a female moth will release a sex pheromone to signal that she is fertile. Male moths can detect and will react to the pheromone message.

There are many types of pheromones (see the Wikipedia article) including alarm pheromones, sex pheromones and food trail pheromones. They are actually fairly common in the animal world.

Pheromones in humans
Humans are animals so it would make sense that we would also produce and react to pheromones. They are evolutionarily useful after all.

For a variety of reasons (discussed in the article) there has been controversy about the existence of human pheromones. To me it seems pretty obvious that something is going on in humans too, and that is what the article is about.

Human examples
There are several examples of the unconscious effects of human pheromones:

• It has been shown that women living together will gradually synchronize their menstrual cycles. Later experiments showed that the sweat of women in different stages of their menstrual cycle could affect the cycles of other women. Sounds like pheromones.
• Brain scans have shown the ‘sex centre’ of women’s brains lighting up when they were exposed to the smell of a male sex hormone (found in men’s sweat). Interestingly the effect was only reliable when there was a man in the room.
• Alarm pheromones can also be subconsciously detected by humans. Test subjects were able to distinguish between the sweat of people who had watched scary movies and people who had watched funny movies. This was despite not being able to consciously tell the difference.
• In a similar experiment brain scans showed the fear centre of the brain lighting up when subjects were exposed to the sweat of first time skydivers.

Very interesting stuff. Luckily the effects seem pretty weak because it could get crazy if we learned to reliably affect people’s behavior using chemicals!