Large between individual differences in taste and smell perception exist. Some people experience higher taste intensities than others due to their genetic make up. PROP tasters are an example of this. Next to genetic differences, the most important factors determining taste and smell abilities are age and sex. Differences in taste and smell capability can be due to anatomical and physiological reasons, but also due to differences in neural networks in the brain, and cognitive processes (innate versus acquired).

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 recognize or name tastes and smells.

Elderly

From research, we know that the sensory acuity diminishes 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] But taste memory, that is 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 that the internal representation of the prototypical food is adapted to their perception. So there is no clear evidence that changing the taste intensity of foods will change optimal preferred concentrations. We also know that within the chemical senses, the sense of smell is more prone to loss with age compared to the sense of taste. As you may realize 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 book.

Sex

Biological sex affects odor perception. A recent systematic review from Sorokowski and colleagues (2019) shows that women are systematically better than men when it comes to the olfactory system. They found differences in all three subdomains which were investigated in the studies they reviewed; odor identification, odor discrimination, and threshold detection. The effect was most pronounced in the odor detection test compared to the identification and discrimination test. There is evidence that hormones can play a role in this, or amount of neurons. On the other hand, it may also be that these different tests are more targeted towards odors that are (generally) more familiar to women than to men.^[3] As we know, odor memory is mainly formed by exposure to odors which may affect the test results. However, it may also be that women have higher cognitive awareness of odors, 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. Usually, these traits are 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 discussed below:

• Taste blindness. A minority of people have specific taste blindness, the inability to detect certain bitter chemicals. About one-third of Europeans carry this trait.^[5] For phenotypical taste blindness to occur, both parents must pass on the recessive gene.
• Specific anosmia is the inability to detect a particular odor while still being able to smell other odors 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 a cause of old age or disease.
• Color blindness can influence food perception. Assessing whether a food is ripe or fully cooked can for example be more difficult. Color 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 color blindness, is rarer, affecting 1 in 30,000 people, and results in seeing only shades of gray.^[7]