There are large individual differences in taste and smell perception. Some people experience higher taste intensities than others due to their genetic make-up. But also the anatomy of the taste and smell organs, differences in neural processing in the brain, physiological status and age affect taste and smell perception.

During the life span, perception also differs. For example, exposure affects smell and taste preferences, see for example the difference between innate versus acquired taste preferences.

Children

It is known that the number of specific taste cells develops in the first 10-20 years of life and then declines with age, and it is also known that the number of functional taste cells is an indication of taste perception. There is a whole field of research investigating the anatomy of the taste organ, that is, the size and number of taste pores, types and number of taste papillae, and number of taste buds in relation to taste perception ability^[1].

During life, there are also considerable changes in the brain. It is also suggested that the brain regions that integrate sensory signals are not fully matured yet in children and that therefore their taste and smell perception is different. Another factor is cognitive development; children may simply not be able to recognise and name tastes and smells.

Elderly

We know from research that flavour perception decreases with age. That raises the question if the optimal preferred concentrations of tastants, such as sugar and salt, are also higher for the elderly.

According to the research of Mojet et al. (2015), it appeared that the optimal concentration of tastants is not related to the ability to the threshold sensitivity of the perceived supra-threshold intensity. It appeared that liking was similar for young and elderly subjects, thereby implying that other factors than taste sensitivity are more important^[2].

Taste memory — the expectation of how a food should taste — may be of large importance. It may be that the decline in the ability of taste is so slow, that the elderly are not aware of this change and their idea of how food should taste may change to match what they can still taste, still matching their perception. There is no clear evidence that changing the taste intensity of foods will change optimal preferred concentrations in the elderly.

We also know that the sense of smell is more susceptible to diminish with age compared to the sense of taste. As you may realise by now, smell is much more complicated than taste, so there are no consistent results yet on how we can affect food preferences and intake using smell manipulations. There is, however, a whole line of research investigating this, but that goes beyond the introductory nature of this textbook.

Sex

Biological sex affects odour perception. A recent systematic review from Sorokowski and colleagues (2019) shows that women perform systematically better than men when it comes to the olfactory system. They found differences in odour identification, odour discrimination, and threshold detection. The effect was most pronounced in the odour detection test compared to the identification and discrimination tests.

There is evidence that hormones or the number of hormones may play a role in this. On the other hand, it may also be that the odours used in this type of research are more familiar to women than to men^[3]. However, it may also be that women have higher cognitive awareness of odours; they simply pay much more attention to them. Nevertheless, sex should be taken into account in olfactory studies.

Regarding taste, studies indicate that women generally possess a better sense of taste compared to men. They are more skilled at distinguishing and describing different tastes. Additionally, women tend to have more fungiform papillae on their tongues. This enhanced taste sensitivity is believed to be linked to evolutionary roles in protecting offspring^[4].

Genetics

Hereditary factors can influence one’s sensory perception. These traits are usually recessive. Genetic factors have been associated with sensory perception and food consumption, but no causal relationship has been established.

Three types of genetic causes of sensory perception are highlighted below:

• Taste blindness. A minority of people have specific taste blindness — the inability to detect certain bitter chemicals, such as PTC (Phenyl Thiocarbamide). About one-third of Europeans carry this trait and cannot taste this bitter tastant^[5]. For this phenotypical taste blindness to occur, both parents must pass on the recessive gene.

• Specific anosmia is the inability to detect a particular odour while still being able to smell other odours normally. This condition occurs when an individual lacks the receptors necessary to detect certain chemicals. For example, some people might be unable to smell androstenone, a compound found in sweat^[6]. Specific anosmia is different from general anosmia, which is the complete loss of the sense of smell. Specific anosmia can both be hereditary or caused by old age or disease.

• Colour blindness can influence food perception. For example, assessing whether a food is ripe or fully cooked can be more difficult. Colour blindness is more common in males because the genes for it are located on the X chromosome, of which males have only one. The most common type is red-green dichromatism, affecting 1 in 12 males and 1 in 200 females. People with this type see blue and yellow clearly but confuse red, green, brown, and orange. Monochromatism, or complete colour blindness, is rarer, affecting 1 in 30,000 people, and results in seeing only shades of gray^[7].