I'll explain the question with an example. Consider Gustation: glucose tastes sweet, bitter gourd tastes bitter and salt tastes salty. Now, sweet obviously feels good but suppose there is an alien species whose biochemistry is different from us, they don't use glucose as a fuel. Now glucose maybe toxic to them so they experience a bad taste whenever they ingest glucose. In this case, the sensation is different!
Another Example would be Photoreception. How is it decided that light having wavelength of 700–635 nm would be considered red and not blue? I know that your answer would be "This is because light of this wavelength stimulates the red cone and not the blue one." Then my question would be why stimulating the red cone gives us the sensation of red colour and not of blue colour?
Similarly, Why does air of temperature higher than our body gives us a sensation of "Hot" and not of "Cold"?
I know that having different sensations for different stimuli affects our reproductive fitness. Those which can detect changes in the environment are more likely to survive than those which don't. Those which developed "sweet sensation" for glucose can gain more energy than those who don't. But it doesn't explain the relationship between the experience of a stimulus and the stimulus.
It seems like our own body has invented experience and sensation and these phenomena don't have any physical significance.
