Eating Behaviour PSYA3 Miss Bird

Biological explanations of eating behaviour AQA A Specification   Eating behaviour Factors influencing attitudes to food and eating behaviour. For example: cultural influences; psychological influences (mood); and social influences (health concerns/media). Explanations for the success and failure of dieting. Biological explanations of eating behaviour Neural mechanisms involved in controlling eating behaviour. Evolutionary explanations of food preference. Eating disorders In relation to either anorexia nervosa or bulimia nervosa: Psychological explanations. Biological explanations, including neural and evolutionary explanations.

Evolutionary explanations of food preference The goal of any evolutionary explanation is to discover the adaptive function of a particular behaviour i.e. what is the purpose of that particular behaviour? The mechanisms that make up human nature were designed by natural selection millions of years ago. Therefore we need to consider the problems faced by our distant ancestors to discover why behaviours, such as food preferences, evolved in the first place.

Evolutionary explanations of food preference Darwin’s theory of natural selection states that individuals will behave in such a way as to maximize their survival and their reproductive potential. Individuals that survive maturity are more likely to produce offspring and be able to ensure the long-term survival of their young. Therefore, in terms of evolutionary theory, it pays to be healthy in terms of what we eat in order to survive and pass on our genes to our offspring.

The evolution of food preferences (A01) The environment of evolutionary adaptation (EEA) Early diets were dependent on the environment that humans found themselves in. Early humans had a vegetative diet. However it is unlikely that they would get enough nutrients from a vegetative diet alone. Therefore our human ancestors began to include meat in their diets. Consequently our preferences for fatty food today (e.g. meat) would have been adaptive for early humans as a source of energy. They would need this energy (from fatty food) in order to survive and to hunt for their next meal.

The evolution of food preferences continued… (A01) Evidence from fossils suggests that our ancestors daily diet consisted primarily of animal-based foods, in particular organs, which are a rich source of energy. A meat diet full of densely packed nutrients provided the catalyst for the growth of the brain. Meat supplied early humans with all the essential amino acids, minerals and nutrients they required, allowing them to supplement their diet with plant-based food that have few nutrients but lots of calories for energy (e.g. wheat).

A01: To summarise… Our modern preferences for calorie-rich/fatty food can therefore be traced back to the adaptive problems faced by our ancestors. I.e. we prefer foods that are high in calories so that we can supply our brains and bodies with the energy that we need to survive and reproduce.

Independent task (A02) Read the study by Gibson and Wardle (2001) and answer the questions in your booklet. You have 10 minutes.

Gibson and Wardle (2001) provided evidence to support the importance of calories in an ancestral diet. They showed that the best way to predict which fruit and vegetables would be preferred by four-to-five year old children was not in terms of sweetness, protein content or familiarity, but in fact calorie content. Bananas and potatoes (which are particularly calorie-rich) were more likely to be chosen by the children, therefore demonstrating an evolved preference for calorie-rich foods. 4-5 years old Sweetness, protein content, familiarity and calorie content. Children more likely to choose calorie-rich options. Needed for energy in order to survive and reproduce. This research supports the idea that there is an evolved preference for calorie-rich foods that are essential for survival.

P.E.E.L (A02) P: There is research evidence to support the evolutionary explanation of food preference, particularly for calorie-rich/fatty foods. E: Research by _____________ has shown... E: This suggests/shows... L: This supporting research evidence by _____________ suggests that the evolutionary explanation is a valid explanation of food preference.

Pair taste test (OPTIONAL) One of you will be the participant and the other will be the experimenter. The participant will be blind-folded and will take part in a taste preference test. You will try 4 different food substances, and between each food you will have a drink to cleanse your pallet. The experimenter will provide the participant with the 4 different foods and record the ratings/facial expression for each taste on A4 paper. You will use a rating scale of 1-10 with 1 being ‘absolutely disgusting’ and 10 being ‘absolutely amazing’. You have 10 minutes!

What do we like (and not like)? Who can identify some different tastes from the taste test? Sweet – identify foods rich in carbs to provide us with energy. Sour – associated with food that has gone off and therefore should be avoided. Salt – critical for functioning of the cells and therefore need to identify. Bitter – associated with poisonous plants, should be avoided.

A01: Predisposed to food preferences? There is evidence that we are born with innate genetic predispositions for basic tastes and that these influence our food preferences. One suggestion is that we are predisposed to prefer sweet and salty foods and to reject bitter and sour foods. Support comes from neophobia in young children What is neophobia? Unwilling / reluctant to try new foods. Neophobic infants are more likely to reject new foods in favour of those that are already familiar to them. This suggests that we are predisposed to be conservative in our food preferences.

A01: Why do we like chocolate? We have an innate preference for sweet things (Rozin, 1982). Why? Sweetness indicates the presence of sugar which in turn indicates calories needed for energy. Evidence from human biology that we are sensitive to sugar. The nerve that runs from our tongue to our brain carries more fibres that are sensitive to sweetness than any other flavour sensation (i.e. bitterness, sourness or saltiness).

A02: Support for innate sweet preference Desor et al (1973) Investigated babies food preferences based on facial expressions and sucking behaviour. New-born babies (only 1-3 days old) demonstrated innate preference for sweet-tasting food. Rejected bitter tasting substances. Why were newborn babies studied?

Why don’t we like bitter and sour? These taste receptors help us to identify food that has gone off. Leads to the facial expression of ‘disgust.’ This is seen in human infants and other primates. Suggests innate. This feeling leads to avoidance of bitter and sour tasting foods.

A02: Supporting research evidence Meiselman et al (1989) – all cultures seem to prefer sweet tastes to any other suggesting inherited food preference. Bell et al (1973) – Eskimos in Alaska lack sweet foods in their diet. However they are quick to accept sweet foods into their diets when they come into contact with them, even though they have no experience of them. Supports the idea of an underlying innate preference for sweet foods.

P.E.E.L (A02) P: There is research evidence to support the evolutionary explanation of food preference, particularly for sweet tastes. E: Research by _____________ has shown... E: This suggests/shows... L: This supporting research evidence by _____________ suggests that the evolutionary explanation is a valid explanation of food preference.

A01: Associative learning “We are predisposed to learning food preferences by associating foods with the context and consequences of eating them.” (Birch, 1999). More inclined to avoid foods that made us ill in the past. Prefer flavours that have been previously paired with a preferred sweet taste or with nutrients that supply us with energy e.g. sugar. These predispositions are highly adaptive as they reduce the likelihood that young children will eat harmful substances (often indicated by sour or bitter tastes), therefore increasing the probability of their survival.

A01: What is taste aversion? LEARN TO AVOID CERTAIN TASTES TO ENSURE SURVIVAL. First found by farmers trying to rid themselves of rats. Difficult to kill rats using poisoned bait as they would only take a small amount of any new food, and if they became ill, would rapidly learn to avoid it. Learnt to associate taste of certain food with symptoms (e.g. vomiting) caused by poisonous substance, therefore developed an aversion to it and would avoid it in the future.

A02: Supporting evidence for taste aversion Garcia et al (1955) – first to study taste aversion in lab Rats were given saccharin- flavoured water and shortly after were exposed to radiation (which made them feel ill e.g. nausea). When given the saccharin-flavoured water again, they avoided it. Therefore had developed an aversion to saccharin as they now associated it with illness. Suggests that they had learned to avoid certain tastes to ensure survival supporting evolutionary explanation of eating behaviour.

A02: Evaluation of taste aversion The development of taste aversions would have helped our ancestors to survive because, if they were lucky enough to survive eating poisoned food, they would not make the same mistake again. Such aversions are very hard to shift – an adaptive quality designed for survival.

A02: Evaluation Could early humans have been vegetarian? Cordain et al (2006) Argued that early humans consumed most of their calories from sources other than saturated animal fats i.e. plant-based foods. This has led to the suggestion that our distant ancestors were healthy eaters and may even have been vegetarian. However, evidence shows that all societies today display a preference for animal foods and fats (Abrams, 1987). Also, if early humans were completely vegetarian would they have been able to get sufficient calories from plants and grains in order to survive?

A02: Evaluation It has been argued that not all food preferences are a product of evolution. A trait that is beneficial today (e.g. consumption of low cholesterol foods) would not have evolved because of its beneficial effects for our ancestors. Our ancestors viewed saturated animal fats as important for energy (and survival!) whereas today we view them as harmful and try to avoid them in order to survive and stay healthy. Indicates a change in food preferences over the years.

A02: IDA Cultural differences: Innate responses do not account for the broad range of food likes and dislikes that develop beyond infancy. Evolved factors important in food selection but these are modified by our experience with different foods in our culture. Real-world applications: Research on taste aversion has been helpful in understanding the food avoidance that can sometimes occur during the treatment of cancer. Some cancer treatments can cause gastrointestinal illness. When this illness is paired with food consumption, taste aversions can result.

Pair task: IDA In pairs, apply relevant IDA to the evolutionary explanations of food preference. Write your ideas down in the box on your worksheet. You have 5 minutes.

IDA Methodological – studies in laboratory – controlled observations but may lack ecological validity. Ethical – research on taste aversion in rats – distressing? Can findings be generalised? Deterministic – food preferences due to evolutionary factors, ignores social, cultural, psychological and cognitive influences. Nature vs. Nurture – suggests food preferences are strongly influenced by genetic factors passed down through the ages and heavy emphasis on innate food preferences from ancestors to aid survival.

Plenary: Consolidation For each term or name in the table, colour code whether it is linked to neural mechanisms in eating behaviour or evolutionary explanations of food preference. You have 5 minutes. Q&A on key terms.

Homework  Complete the essay structure and gap-fill IDA paragraph in your booklets. Revision aid on evolutionary explanations of food preference.