Neuroscientists at the University of California, Berkeley have conducted an experiment that explains how we are able to keep from being overwhelmed by constant sensory input from odors. The researchers used MRI technology to monitor the brain activity of two groups of volunteers, only one of which was told that the experiment was about odor. When both groups were exposed to odors, the group that did NOT know the experiment was about odor showed less activity in the areas of the brain that process odor.
It turns out that the brain is detecting and processing all the odors around us, but a particular area of the brain actively tunes this out unless the odor reaches a high level, such as when we walk into a cloud of cloying perfume or step in dog poop.
When we want to sniff for odors, however, the brain releases the block and begins to pay attention to the smells around us. It even tunes in very precisely to specific smells, allowing us, for instance, to search for a hint of blackberry in a glass of zinfandel.
I wish they had tested how well the volunteers did at finding particular odors, and whether they were better able to detect them when they knew what they were looking for. It is rather off the topic of the experiment, but I find testing a new perfume much more rewarding when I already know at least some of the notes. If I don't know the notes, I usually try to decide what other fragrance it smells closest to, and apply that fragrance to my other arm. This allows me to focus more closely on what notes are "new" in the fragrance I am testing.
Enough about my problems, you can read the rest of the article at physorg.com. The Social Issues Research Center also has a nice page on the sense of smell.
I'm the same way. It's very difficult for me to pick out individual notes unless I know what to sniff for. One of my most enjoyable activities is to dab a new scent on my wrist and sit at the computer and read the description and reviews. It helps me to form my own impression.
I do the same! I must admit it doesn't always help, that is, sometimes I still can't smell what everyone else does.
I always tried not to read the notes first, because they're all a fiction anyway. If I wanted to clarify some impressions (because I don't know what different flowers smell like, mostly, and I wanted to describe them) I would check a listing of notes, but always with the impression that because so many perfumes are synthetics that can smell like such strange combinations of things, any list of notes was probably mainly an interpretation. In that way, I could say with confidence that I smelled what I smelled and that I wasn't hallucinating something in there because of the power of suggestion.