The attention of small children is very often solicited by calling out to them: “look” or “listen”. We also say “taste it”, but more rarely “smell it”, ignoring the fact that what we call “taste” is certainly due to the flavours perceived in the mouth, but mainly to the aromas captured by the sense of smell.
You can check this with a simple experiment. Pinch your nose before putting food in your mouth. Chew it: “It doesn’t taste good! Open your nose: “It tastes good ! Indeed, when we eat, odorants are released in the mouth and go up to the nose through the back of the throat (pharynx) to reach the olfactory epithelium where they are smelled like the odorants inspired by the nostrils; this is the retro-nasal route. But, as the two sensations coincide, they are amalgamated under the name of taste.
We attach great importance to vision and hearing, which are our dominant senses. But the loss of smell (anosmia) reveals its importance in our daily lives, as some victims of covid-19 have shown.
For the sense of smell, while it is very useful for appreciating food, also plays an implicit, but often crucial, role in human relationships, in our relationship with ourselves and with the environment.
Unfortunately, at least in the West, this sense is neglected and education leaves it untouched, leaving it to be learned at random from life’s experiences.
However, the sense of smell functions from intra-uterine life. Between 4 and 6 months of gestation, the nose opens up, allowing the nasal circulation of amniotic fluid which brings in the mother’s odours (Schaal, 1988).
And, as the olfactory sensors in the nose are functional in the last third of pregnancy, the fetus can accumulate a prenatal olfacto-gustatory experience that it will express at birth (Valentin and Chanquoy, 2012).
Researchers tested this transnatal memory by having future mothers taste aniseed. When the babies were born, they showed a preference for the smell of aniseed, whereas the babies in the control group showed indifference or aversion (Schaal et al., 2000). But for the newborn, and then for the rest of his life, the most important smell is that of his mother. It is she who guides him to the breast to suckle (Varendi et al., 1996). Then, it is thanks to breastfeeding that he will enrich his olfactory repertoire because not only does the composition of breast milk evolve very quickly according to the child’s nutritional needs, but he also carries with him the diversity of aromas from his mother’s diet (Nicklaus et al., 2005).
At the same time, these early sensory experiences usually take place in an environment that is reassuring for the baby, which favours their memorisation.
Here again, researchers have looked at the consequences of this early learning. They have found that breastfeeding, followed by diversification of the diet after 5 months, not only promotes diversity of diet at the age of 6, but also curiosity about new dishes (Maier-Nöth et al., 2016). The child is therefore better equipped both to diversify his or her diet and to enjoy it, which is good for his or her physical and mental health.
However, this early learning, which is largely implicit and little verbalised, is not just about food. In doing so, as with the other senses, the baby also becomes imbued with the family culture and enters the circle of human olfactory communication, which is largely ignored. Yet, if a family member is offered several body odour T-shirts, children are able to recognise their own smell (Lord and Kasprzak, 1989; Perl et al., 2020), those of their siblings and those of their parents (Russell, 1976). Conversely, parents recognise a T-shirt worn by their child (Porter, 1998; Dubas et al., 2009).
Often perceived in a non-conscious way, our body odours tell us a lot about ourselves: our age, our gender, our health status, our diet. Common language tells us that we can ‘smell’ or (more often) ‘not smell’ someone. And, in couples, we see, again in the T-shirt test, that we generally prefer the smell of our partner to any other smell.
Furthermore, emotions are perceived through the nose, and they can be contagious, such as the smell of anxiety or fear (Prehn-Kristensen et al, 2009), or the smell of tears (Gelstein et al., 2011). And, among the reasons why anosmics are very unhappy is the inability to smell others, and oneself.
Olfactory sensations are fleeting and rapidly changing. To grasp all their facets, one must exercise one’s attention, memory and curiosity. There are hardly any scientific articles on the benefits of olfactory training for small children. However, it is known that in older children, and even in adults, this exercise enables them to reach, if not an expert level such as perfumers, oenologists or cooks, at least an enlightened amateur level that enables them to describe and appreciate olfactory sensations in the same way as visual and auditory perceptions (Jehl and Murphy, 1998).