||P.9 5th paragraph: "Beyond arguments by analogy, some recent studies of human olfaction suggest that the perceptual
space for odors may have rather few dimensions. Furthermore, the dominant axes of this perceptual space can be related systematically to the physical characteristics of odorous molecules (Secundo et al., 2014). Another relevant observation is that mixtures containing many (>20) diverse odorants
tend to smell alike, even if they don’t share any molecular components (Weiss et al., 2012), a phenomenon that has been termed ‘olfactory white’, in analogy to the ‘white’ percept associated with a mix of many colored lights. This suggests that the dimensionality of odor percepts may be
around 20 or less. Table 1 summarizes the number of dimensions of various spaces discussed here."