Not only are smell receptors arranged in patches, research shows, but the patches are organized along an axis of yucky to pleasant.
These findings across the senses show that we begin to organize our sensory world even at the first instant where the stimulus encounters the body. "The earliest stage of perception is already organized to match the perceptual world," Sobel said.
For smells, Sobel explained, odor pleasantness is related to the structure of the molecules that we smell. "Molecules that are small and dense tend to be unpleasant," Sobel said. "Molecules that are large and floppy tend to be pleasant. There is a correspondence between the principle axis of structure and pleasantness."
This all means that our smell preferences are, to some extent, hardwired.
"Newborns have odor preferences straight up," Sobel said. Lab rats bred in captivity for 1000 generations still have a fear response to fox odor, he added.
Researchers previously thought that smell receptors were randomly and uniformly spread over the nasal epithelium, the surface high up inside the nose that detects smells, said Sobel.