Kat - The answer here is something to do with adaptation and desensitisation. It's the same reason why you're not sitting there going, 'Oh gosh, I'm not wearing clothes! Oh, I'm sitting on a seat!' all the time. If that happened, if our nerves responded to every stimulus we're getting all the time we would just be overwhelmed and wouldn't know what to do. What happens if you're sniffing vinegar or something with a really strong smell? It goes under your nose, up into your nose and it activates something called olfactory neurons. These are basically smelling nerve cells up in your nose and they send a signal to your brain that says, 'This is a really strong smell, this is what it smells like.' The signals that are being sent by those neurons are in the form of chemicals, little chemical messengers. They kinda get worn out. They run out of chemicals in these cells. Something called desensitisation happens. You stop being able to smell the smell. This is very important because say if you're - if you think back to our ancestors sitting around in the jungle or in their cave - you want to spot new things happening to you. You don't need need to know about what's going on that's already happening to you. You want to spot new stuff. Something like a very strong smell you need to spot it when it's new and it's happening so it can be over the level of noise that's going on around you. What happens if you're smelling a strong smell after a while you'll stop smelling it, basically. Anyone who's lived with boys and particularly whiffy toilet habits will know this. Chris - The evidence is that men and women make equal amounts of smells, equally often during the day.

Kat - Yeah, yeah...