|Comments on Friday 19 December 2008:|
|There was a thing on Q.I. a while back about "how many senses do we have?" They were saying many, citing, eg. hunger, where-your-limbs-are, and balance. Today I have been pondering what there is that actually are distinct senses. Balance is really just touch in the ear-tubes, where-your-limbs-are might not even be a sense so much as an expectation that they'd be wherever you last tried to put them (combined with touch for correction). Hunger could just be internal touch things, though that seems unlikely.|
One fairly unambiguous one is that 'touch' should be at least two senses, 'temperature' and 'pressure'.
I think the key to determining if something should definitely count as a sense is that there should be no way the same thing could be detected using the senses already listed.
I think carbon-dioxide-sense is a strong candidate - if you hold your breath there is no movement or pressure to inform you that you need to breathe, but you pick up on it nevertheless. (This makes me favour hunger as a sense too because it seems similar.)
I wondered about the feeling of caffeine-buzz, but consideration suggests that's a tingling (touch sense), a withdrawal headache (touch?), and not feeling tired (which you don't really feel), so caffeine-buzz is detected purely with other senses. However, that does bring up sense of tiredness as another chemical-based sense.
Then I was thinking endorphins, as from having eaten really spicy food - there's a different feeling there, that isn't just surface, and has no identifiable symptoms - I call that one sense of well-being.
What else do you think qualifies as a distinct sense? And are there some of mine that you think don't? [14:39]
|I don't think balance is just touch, because the thing that you're touching is itself part of you. Once you head down that route, surely all sense can be redefined as just one sense, that of one bit of your body interacting with another. I think it's wrong to consider the microscopic hairs and the liquid as two separate things, in other words: they're two parts of the same sense organ.|
Not at all convinced by your carbon-dioxide sense, either, unless there's evidence of a link from detecting a build-up of carbon-dioxide to wanting to breathe. There are plenty of other candidates, such as instinct. I suspect that, if we were to somehow rig up some clever technology to replace the carbon dioxide in someone's blood with oxygen so that they didn't need to use their lungs any more, that person would still find it impossible to hold their breath indefinitely. But, hey, maybe not. Someone should do that experiment.
Where-your-limbs-are is a sense, I reckon. A good juggler can juggle blindfold, if not for long. And what about when you wake up first thing after moving around at night? You know what position you're in, without being able to remember your movements.
I'm with you on hunger: definitely a sense.
And I'd propose hangover as a sense. The pain is caused by dehydration causing the brain to shrink causing the membranes between the brain and the skull to be stretched. That's not touch.