Gender differences in sensory performance has been studied for a long time, specifically for the sense of smell atleast a century. However most studies that look into this does not find a gender difference in any aspect of olfactory performance. The aspects of olfactory performance encompass (i)olfactory sensitivity, which is a measurement of the weakest stimuli that can be perceived. (ii)Identification which is the ability to name a perceptible odor. The last aspect of olfactory performance is (iii)discrimination ability, which is the ability to separate two or more odorant that are equally intense.

The previously performed studies on olfactory performance that have found a gender difference have always reported that females are better. A gender difference has consitently been found with identification ability, rarely found in regards to sensitivity and never with discrimination performance. So to conclude so far females have been shown to have a keener sense of smell compared to males. Important to remember is that in regards to olfaction it is really hard to make general statements about the entire sense of smell of a subject or group. As there is a vast number of odorants that can interact with our olfactory receptors a study can only make statements about the odorants tested.

During the 1990s it was found that the olfactory receptors were not only present in our noses, but also in other tissues and among these the sperm cells of men. This was found to be not only the case in humans but also several other mammalian species. A hypothesis was formulated as to the function of these olfactory receptors expressed on sperm cells, and it stated that these olfactory receptors should help the sperm to find the egg and fertilize it. It seems unlikely that the sperm cell which has such a specific purpose/function could afford to express olfactory receptors that it does not need that would use precious energy required for swimming behavior. If these receptors indeed take part in the fertilization process they should be subjected to sexual selection as males with more effective or just more of these receptors would be more successful in reproduction.

Recently a study was able to express one of these receptors outside the sperm cell and perform an expirement that assessed which molecules it interacted with. This study found that Bourgeonal, an aromatic aldehyde, was the strongest ligand. This group of researchers further tested how intact sperm cells was affected by exposure to Bourgeonal, and found that sperm cells actively swam towards Bourgeonal. This gave support to the hypothesis of the olfactory receptors in sperm cells aiding fertilization.

My supervisor has performed alot of research on olfactory sensitivity and discrimination performance. He thought it would be interesting to investigate whether there was a gender difference in the human olfactory sensitivity to Bourgeonal. This is how this current study came about, i have determined the detection threshold, which is a measure of the olfactory sensitivity, to Bourgeonal, Helional which is an odorant that is similar in structure to Bourgeonal and to an unrelated odorant called N-pentyl acetate. Helional and N-pentyl acetate was chosen to verify the results, to make sure that if i found a gender difference to Bourgeonal it would not be due to a general hypersensitivity to the group of molecules or some other variable. 250 males and 250 females were tested during the fall of 2008 in my experiment.

The results showed that males infact were more sensitive to Bourgeonal compared to females and that there was no such gender difference for the other two odorants. So this is the first ever study to show that males are more senstive to any odorant. My main argument is that this is because Bourgeonal is more biologically relevant to males than to females. Which is in accordance with the hypothesis that olfactory receptors in the sperm cells help the sperm navigate to the egg.