AQA A-level Psychology: Revision Made Easy - Jean-Marc Lawton 2017
Explanations for food preferences
The evolutionary explanation sees food preferences as occurring due to their adaptive survival value and having been shaped by natural selection to become widespread in the population. Sweet tasting foods are preferred due to their high-energy and non-poisonous content, while salty taste preferences evolved, as salt is essential for maintaining neural and muscular activity and water balance. An ability to detect and reject bitter and sour tastes evolved, as such tastes indicate the possible presence of toxins. Meat eating is not an innate tendency, it has to be introduced into children’s diets, with many reluctant to do so. Neophobia concerns the tendency for infants to dislike or be distrustful of unfamiliar foods. This has an evolutionary protective function, as unknown foods could be toxic. Taste aversion occurs when individuals eat foodstuffs that makes them ill and therefore avoid those foodstuffs in the future. This involves biological preparedness, where individuals are primed by evolution to develop taste aversions more easily to toxic foodstuffs. Learning experiences reduce food neophobia and learning also occurs via social influences, where others’ food preferences impact upon our eating behaviour, and cultural influences, where specific eating practices are transmitted to members of cultural groupings.
Fig 13.1 There is a preference for sweet foods as they are associated with high-energy, non-poisonous content
Go et al. (2005) assessed the role of bitter taste preferences by examining the presence of genes that allow detection of bitter tastes in both humans and other primates. The researchers looked at the prevalence of the bitter taste receptor genes T2R in humans and 12 other primate species to test for an evolutionary ability to detect bitter tastes. The results showed humans have accumulated more pseudogenes (dead genes) than other primates, indicating that humans’ bitter tasting capabilities have deteriorated more rapidly. T2R molecules play a key role in the avoidance of bitter, toxic substances, so the modification of the T2R gene may reflect different responses to changes in the environment resulting from species-specific food preferences during evolution. It was concluded that although humans possess the ability to detect and avoid bitter tasting foodstuffs, perhaps due to environmental changes, natural selection is acting to reduce humans’ ability to detect bitter tastes.
• Denton (1982) found an innate preference for salt in many animal species, suggesting the preference has a survival value and is evolutionarily determined.
• Birch et al. (1987) found that 2 year olds given the most exposure to unfamiliar fruits and cheeses reduced their neophobia of the foodstuffs more quickly, illustrating the role of learning in reducing food neophobia.
• Bernstein & Webster (1980) demonstrated taste aversion in humans by finding that adults given ice-cream before receiving chemotherapy developed a subsequent aversion to eating ice-cream as they had a biological preparedness to associate the nausea with food they had eaten rather than the chemotherapy that had actually caused the nausea.
• Menella et al. (2005) found that although genetic influences shape children’s food preferences, by adulthood cultural influences over-rode genetic ones, especially in the degree of preference for sweet-tasting foods. This suggests that genetic influences shape early food preferences, but culture influences later ones.
The idea of an evolutionary determined preference for sweet tastes has much research support, including cross-cultural evidence. Bell (1973) reported that Inuit people, who had never tasted sweet foodstuffs before, accepted them on their first presentation.
Some children appear less neophobic than others, which has an adaptive value, as they would be more willing to eat unfamiliar foods. If they found them non-toxic their behaviour would be observed and imitated by more neophobic children.
There is an adaptive survival value to observing and imitating others’ eating practices; if others safely consume novel foods, this indicates they are safe to eat, which helps break down food neophobias.
Kendrick (1982) studied cultural groups noted for longevity, finding a common factor was their vegetarianism, which suggests there is a price to pay for meat eating, that of having a shorter lifespan.
With the increase in world population mobility, developments in transport systems and modern food hygiene practices, like the wider availability of refrigeration, eating behaviours are more global and less based on individual cultural locations.
There are individual differences in salt preference, which is puzzling as evolution would predict a standard universal preference. This lowers support for the idea of an evolved salty taste preference.
As many medicines are bitter tasting, children, with their evolved preference to avoid such tastes as they indicate the possibility of toxins, find it difficult to swallow or keep them down. But as children have an innate preference for sweet tastes, sweetening bitter-tasting medicines helps them swallow them.