How smell evokes memories and feelings

Have you ever found yourself transported back in time by a sudden whiff of a forgotten smell? You took your child into primary school for the first time, and suddenly images from your own schooldays flashed across your mind? Or you walk past someone wearing a particular scent and memories of your grandmother come flooding back?

• Have you ever noticed particular aromas that can affect your feelings? Delight at the scent of freshly-mown grass, or sensations of unease whenever you smell a particular furniture polish, perhaps?
• It's because the area in the brain that first receives smell or taste impulses from the olfactory receptors or taste buds is one of its oldest and most primitive parts.
• Known as the limbic system, it also deals with emotions and emotional responses to memory. Only later is the information transmitted further to more recent areas of the brain involved with thinking, where smells and tastes are consciously perceived and interpreted.
• That's why strong smells usually evoke strong responses — people either love them or hate them.
• Distinctive smells also leave lasting impressions that are closely linked to the memory of what was going on when you first smelled them.
• Because the limbic system also controls mood, motivation, pain and pleasure sensations and some hormonal secretions, smells can have a powerful effect on our feelings.
• "Smell is unique among the senses in its privileged access to the subconscious," says smell expert Tim Jacob of Cardiff University in Wales.

• Whether we like or dislike smells is to some extent a learned response.
• Children are often less concerned about odours than adults, though even babies will respond with disgust to the smell of rotten food.
• As we mature, we begin to develop odour preferences, which are influenced by familiarity. That explains, for instance, why urban dwellers who opt for country living may find livestock and manure smells unbearably offensive, while people who've grown up around farms accept them as perfectly normal.

• Learned smell preferences also influence our food likes and dislikes. As you have discovered, much of the flavour of food is due to smell sensations.
• But, unlike taste, humans don't seem to have any innate preferences for particular food smells, other than a general distaste for the smell of rotting foodstuff.
• Whether we like or dislike a particular flavour may then depend as much on the circumstances in which we first encountered it as on its actual taste — but thereafter, if we associate a particular smell with something delicious to eat, it's likely to stimulate our appetite.
• On the other hand, learning is also how we develop an "acquired taste" — repeated exposure to particular flavours tends to overcome original dislikes.