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It seems that there are a great many smell receptors (at least 40, in contrast with only 3 colour receptors). As a result we can all be and probably are smell blind in many different ways. What’s more, our raw sensations of smell may therefore be remarkably different from one another (on average 30% different), but in spite of this there is much commonality in the overt perception of smell, presumably through discussion and cultural learning.
This suggest not only that the ultimate mapping of odorant perceptual space based on genetics might still be a very challenging task, but also that smell is the optimum sensation for studying cultural effects on qualia, as we always suspected.
Mainland et al. find that any two individuals have about a 30% difference in the makeup of their olfactory receptors. Nevertheless, the difference between the smell of roses, violets and asafetida remains relatively constant across individuals, more so than a 30% difference in receptors might imply.