Thanks to scent memory, an aroma you smelled as a child can be recognized many years later.
The sense of smell is closely bound up with memory. The reason you recognize most smells around you with no feelings of unfamiliarity is that every kind of smell is archived with a special code in your scent memory. The moment you encounter an aroma smell, it is identified by application to that archive. A smell you encounter for the first time, which you have never experienced, is interpreted by being compared to other scents. If we did not possess such a memory, smells would be impossible to describe.
Smells also remind us of various events that we experienced in the past. A familiar perfume scented as we walk along the street reminds us of another woman who wears it. The smell of something cooking can evoke a memory of a meal that took place years before. The same aroma can awaken pleasant feelings in one person, but unpleasant emotions in another.
(Figure 19) Information regarding smells is believed to be collected in the hippocampus and amygdala regions of the brain.
Where, then, are the memories of various scents—and the emotions they evoke perceived anew—preserved over the years? Where is the data bank stored, with its very large capacity for information on thousands of different aromas? The answers are not yet known for certain. But information regarding smells is believed to be collected in the brain's hippocampus and amygdala. (Figure 19)
Results of research on this subject are clear: Your memory serves as a data bank of aromas throughout your life, so long as you suffer no serious illness or accident. Furthermore, it has an active structure rather than a stable one, and renews itself constantly in the light of new experiences. Information about a substance you smell for the first time is recorded in memory, making it easy for you to recognize it when you next come across it. Note that cells made up of proteins constitute your olfactory memory, establishing an extensive archive and expanding it as new smells are encountered. As a small comparison, your computer cannot spontaneously update itself. It will remain as it is until you load new programs onto it. Neither did the archival property of the scent memory cells come into being spontaneously. God created them, and their superior design is one of the countless proofs of His mercy and the way that His knowledge enfolds all things. (Surah Ghafir: 7)
One important feature distinguishes olfactory memory from visual and audio memory: Information about smell has a much greater permanence. That is why so many memories are evoked when you perceive a smell originating from a flower, a herb or even from a person. Research has shown that every individual's own scent is unique, just like a fingerprint. (The only exception is with identical twins.) When specially trained dogs follow a suspect, they track the traces of odor of that person's skin , and can distinguish that suspect by means of his unique scent.
Indeed, the report in the Qur'an describing how the father of the Prophet Joseph (peace be unto him) recognized his son's scent years later may be pointing to that very fact. His father recognized the smell as being the same scent that the Prophet Joseph (pbuh) had in his childhood, even after the passage of a great many years:
And when the caravan went on its way, their father said, "I can smell Joseph's scent! You probably think I have become senile." (Surah Yusuf: 94)