The psychological impact of smell is closely linked with memory, probably more so than any of our other senses.
Those with the full olfactory function may be able to think of smells that evoke particular memories; the scent of an orchard in blossom conjuring up recollections of a childhood picnic, for example.
This can often happen spontaneously, with a smell acting as a trigger in recalling a long-forgotten event or experience.
Marcel Proust, in his ‘Remembrance of all Things Past’, wrote that a bite of a madeleine vividly recalled childhood memories of his aunt giving him the very same cake before going to mass on a Sunday.
Olfactory memory refers to the recollection of odours. Studies have found various characteristics of common memories of odour memory including persistence and high resistance to interference.
Explicit memory is typically the form focused on in the studies of olfactory memory, though implicit forms of memory certainly supply distinct contributions to the understanding of odours and memories of them.
Research has demonstrated that the changes to the olfactory bulb and main olfactory system following birth are extremely important and influential for maternal behaviour.
Mammalian olfactory cues play an important role in the coordination of the mother-infant bond, and the following normal development of the offspring.
Maternal breast odours are individually distinctive and provide a basis for recognition of the mother by her offspring.
Throughout evolutionary history, olfaction has served various purposes related to the survival of the species, such as the development of communication.
Even in humans and other animals today, these survival and communication aspects are still functioning.
There is also evidence suggesting that there are deficits in olfactory memory in individuals with brain degenerative diseases such as Alzheimer’s disease and dementia.
These individuals lose the ability to distinguish smells as their disease worsens.
There is also research showing that deficits in olfactory memory can act as a base in assessing certain types of mental disorders such as depression as each mental disorder has its own distinct pattern of olfactory deficits.
Smell and Emotions
In addition to being the sense most closely linked to memory, the smell is also highly emotive.
The perfume industry is built around this connection, with perfumers developing fragrances that seek to convey a vast array of emotions and feelings; from the desire to power, vitality to relaxation.
On a more personal level, the smell is extremely important when it comes to the attraction between two people.
Research has shown that our body odour, produced by the genes which make up our immune system, can help us subconsciously choose our partners.
Kissing is thought by some scientists to have developed from sniffing; that first kiss being essentially a primal behaviour during which we smell and taste our partner to decide if they are a match.
It is likely that much of our emotional response to smell is governed by an association, something which is borne out by the fact that different people can have completely different perceptions of the same smell.
Take perfume for example; one person may find a particular brand ‘powerful’, ‘aromatic’ and ‘heady’, with another describing it as ‘overpowering’, ‘sickly’ and ‘nauseating’.
Despite this, however, there are certain smells that all humans find repugnant, largely because they warn us of danger; the smell of smoke, for example, or of rotten food.
We all have a better sense of smell than we give ourselves credit for.
Over the years, there has been considerable research showing that humans have the ability to detect emotional and physical states with their noses, even though they may not be consciously aware of what they are sensing.
Babies identify their mother by smell, and men’s testosterone levels rise when they sniff a t-shirt worn by an ovulating woman.
Now, there’s new research showing that emotions can be communicated by “chemosignals.”