We develop some taste (and smell preference) very early in life – some children like some foods, others not at all. I think that its a really complex mix of learning and genetic effects.
So, its very hard to know in your particular case. It might be a genetic effect which might have a clear cause (perhaps your distant ancestors were Shahman’s who could tolerate the smell of cannabis, and were hence genetically selected for – bredding super-Shahman’s), might be a random mutation of unknown function, or there might be a “good” genetic reason that isn’t yet clear to us.
We can learn to like smells because of a “positive association”. Perhaps you were in a good mood (cough) the first time you smelt cannabis, and so this smell is now associated in your brain with a good mood – the association is now strong enough to trigger a good mood. A scientist called Ivan Pavlov was famous for doing experiments to generate this type of “association”, now called “Pavlovian Conditioning”. He did things like teaching dogs to associate bells and lights with food, so they learnt “positive” responses to them. Some psychologists still do a lot of work in this field.
By the way, smells are processed in a very old part of the brain (the paleocortex – literally, the “ancient” cortex) and are very closely associated with subconscious changes in behaviour and mood. So, the link between a smell and a mood is a very common one!
PS: I wouldn’t recommend taking cannabis – there are better things to get high on, like science!
It’s very hard to know the answer to this one without knowing your history first Hubbard!
A lot of our reactions to smells comes down to positive association – this is where you link a particular emotion or reaction to a smell (a great example is chocolate – why do we smell chocolate and think ‘mmm yummy!’). This could well have happened with you. Failing that, it could be something to do with your genetics themselves – it is very hard to know straight off!