With over 400 receptors in the nose, humans are able to distinguish thousands, millions, or even up to a trillion scents, and develop odour memory.
A sniff of chlorine might bring back a specific pool-related memory. A whiff of fresh-baked bread might bring back a specific childhood-related memory. Experts also say that the association of emotional responses to smell may be borne by the fact that different people can have completely different perceptions of the same smell. This plays an important part in the psychological make-up of individuals.
On a more personal level, smell has proven to be important in the attraction between two individuals. Kissing is also thought to have developed from sniffing; a primal behaviour during which an individual smells and tastes his or her partner to decide if they match.
But despite the pervasiveness of smell, science has provided more explanation for visual and auditory memory, compared to smell memory.
The science behind odour memoryA classic example of smell memory is known as Proustian memory (or involuntary memory), where an exposure to a stimulus can trigger a strong memory from the past - such as the chlorine or baked bread examples.
This strong association of odour with emotion is thought to be the result of the olfactory bulb being positioned within the limbic system. The olfactory bulb is close to the amygdala, known to process emotion, and the hippocampus, which is responsible for associative learning. This "tight wiring" explains why smells are able to trigger memories.
For Berlin-based scent artist Sissel Tolaas, she has used this connection to create the Smell Memory Kit.
"Visual memory remains 30% after three months, smell memory remains 100% after one year," says Tolaas. "Why not use that?"
In 2016, Tolaas worked with Vienna's Supersense Lab to create the first commercial product that takes "smell snapshots". The intention is to create a stronger memory of a specific event that an individual wants to remember - a wedding or a trip.
To take a "smell snapshot," an ampoule containing a particular scent is cracked open during the event and the user takes a whiff. According to Tolaas, in the future, when the user takes a sniff at the same ampoule, the scent would bring back the memories of the moment.
“Smell is so connected to the emotions in humans, you’ll never forget,” Tolaas says.
Short-term odour memory, a challenge to a scientific factBut how much truth is there to Tolaas' statement?
Not all smell is stored in long-term memory, some are just temporarily stored - for example when shopping for a new aftershave or perfume. Scientists from Bournemouth University have been studying this phenomenon. They looked at how people store odours in short-term memory and how odour memory differs from other types of memory.
They found that to some extent, short-term odour memory happens when odours are hard to name but they also found that some people are able to store the actual odour within memory. This is supported by research showing that different parts of the brain are activated when remembering easy-to-name and hard-to-name odours; specifically, the inferior frontal gyrus and the piriform cortex, respectively.
The loss of odour memory as a diagnostic test
Regardless of short-term or long-term odour memory, the sense of smell has been proven to play an important part in the psychological make-up of an individual.
The absence of smell can have a profound impact. Anosmia sufferers often describe isolation and feeling cut-off from the world around them, experiencing a 'blunting' of emotions. Smell loss has also been shown to affect the formation and maintenance of close personal relationships, leading to depression.
But it is also an indicator of something more serious. Smell loss occurs with both Parkinson's disease and Alzheimer's, and studies have indicated that an impaired sense of smell can be an early sign of the onset of both conditions, often happening before motor skill problems develop. MIMS
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