Genetically-determined Sensitivity to Aromas and Flavours
Individuals occasionally possess dramatically different sensitivities to various aroma and flavour structures. Evidently, there exist large, genetically-determined individual differences among individuals in terms of their sensitivity to aromas and flavours. Some people are completely insensitive to certain substances, although others can be extremely sensitive to the aroma or taste of these substances.

It is certain that people react positively to sweet and umami flavours as early as immediately after birth. A salty taste, apparently, should be viewed ambivalently, since a preference for salty flavours only develops after some months and, as well, depends on the concentration of salt. It is more difficult to judge whether preferences for or aversions to certain aromas are in-born. It has been shown in earlier studies that babies react positively to the smell of vanillin, butter and banana; in contrast, they dislike the smell of shrimps and rotten eggs. The significance of these investigations, however, was later qualified, including by later studies having showed that a positive reaction of neonates to the aroma of vanillin is not demonstrable with absolute certainly. It is only clear that, on the grounds of the studies to date, new-born babies react immediately and positively to the aroma of amniotic fluid, breast milk and to the maternal body odour.

Learnt Taste and Smell Sensations
A range of studies suggests the assumption that, at least in early childhood, even as early as in the womb (in utero), certain smell or taste sensations can be learnt. This occurs, e.g., by their being received via the amniotic fluid or the breast milk. In general, however, the investigation of the positive or negative assessment of smell or taste sensations is astonishingly difficult. For example, it is not necessarily the case that odours and flavours associated with a positive effect (e.g. a gain in energy and satiety) result in generally positive reactions. Hence, in tests e.g. the aroma of methional, which has the odour of boiled potatoes, was even rated as “very unpleasant”, although the subject concerned enjoyed eating potatoes very much. In all likelihood, more complex mechanisms are involved in the reaction to aromatic substances.

 
Learning Principles for Food Preferences and Aversions
Social learning is an importing learning principle and, with it, the environment in which humans grow up and live, the customs of which the individual observes and through which he learns. In close association with this is the often repeated exposition that it can be shown in infants that, in the end, they can accept bitter fruits which they initially refused just as well as a diet of carrots, which tasted good to them from the beginning, due to repeated offering. It seems to be important in this context, however, that where the offer is repeated, the child should not be forced, since this can completely reverse the result. Some studies suggest that certain preferences developed in early childhood are still retained until some years later.

Sensory Training as a Basis for Diet Rich in Variety
It seems to be a promising method to nurture and train the sensory “receptiveness” of children by presenting them, even at a very young age, with a variety of taste and aroma sensations. It seems to be important in this learning process, however, that children associate “That makes me full” with a certain flavour or food. It is certain, however, that in learning a diet rich in variety, as with learning many other things for daily life, the ideal way is that, above all, children can have their experiences themselves.