However, a study in the February issue of Nature Neuroscience says your brain's response to such strong pleasant and unpleasant emotions are actually quite similar.
The researchers had study subjects smell pleasant and unpleasant odors at different concentrations. Using brain imaging to observe the subjects' brain reactions, the researchers discovered that a key area for brain emotion -- the amygdala -- responded equally to both the pleasant and unpleasant odors, solely on the basis of their emotional intensity.
The amygdala has been regarded as an area that responds mainly to negative emotions. However, this study suggests that may be partly an illusion, caused by the correlation between unpleasantness and arousal.
Here's where you can learn more about the workings of your nose.