Hi,
I think we do feel 'wetness' by temperature change, after all, water is a pretty good conductor of heat when compared to say...wood. And sometimes the equipment I work with feels 'wet', but it isn't, its simply because its metal thats been stored in a car over night, so its cold.
I heard something interesting on the radio last week about feel and taste. They mentioned some research group produced 'evidence' that senses generally work together, for example, 'flavour' is a combination of taste, touch (in the mouth) and sound and vision. Ever dyed a food blue and got someone to taste it? they usually hate it, no matter what it is.
How on earth the brain processes this information I don't know, but it might as well be different for everyone, we're all different. And each 'sense' measures many different things, I mean, 'touch' for example:
temperature
pressure
difference in pressure (is something solid? or does it move)
and difference in 'feel' between parts of the body, like in the finger, for 'texture'.
I also read in New Scientist a while back (can't remember) that the human eye can detect a single photon. However, because that is not very useful, and the brain would be bombarded by such information, the brain filters out these signals, and only registers 'light' when there are roughly 10 or more photons. That made me wonder what else our brains filter out. If our senses are much more 'sensitive' to real world information, and the brain ignores most of it what, then surely we could find a way to not filter.
As to how a 'robot' would use sensors, I think the key is combining them. use all the inputs it has available to measure something, and then store this information for latter reference.
my two cents (ps, I'm really just an electronics guy)
Blueteeth