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EATING BEHAVIOUR - Coggle Diagram
EATING BEHAVIOUR
neural and hormonal explanations involved in the control of eating
definitions=
hormonal mechanisms
= chemical messengers within the body that influence eating behavour
neural mechanisms=
the influence of brain components in regulating eating behaviour
hypothalamus=
a small brain structure associated with the regulation of eating
lateral hypothalamus=
part of the hypothalamus asssociated with hunger and onset of eating
ventromedial hypothalamus=
part of the hypothalamus associated with the cessation of eating
dual control theory= a homeostatic view of eating- where hunger motivates eating which leads to satiety and cessation of eating
dual control theory
lashley believed neural mechanisms were involved in making decisions of when and when not to eat. did experiments with rats and identifid hypothalamus as the brain area that plays a key role in food intake
lateral hypothalamus (LH) = "hunger centre"- initiating eating behaviour
ventromedial hypothalamus (VMH) produces the feeling of fullness linked to the stopping of eating.
the DCT is based on the homeostatic perception of hunger and fullness (satiety). when glucose levels are low, liver sends signals to Lateral hypothalamus which creates a sensation of hunger which motivates the individual to eat
food is eaten which releases glucose and activates ventromedial hypothalamus creating the sensation of fullness
therefore, the hypothalamus helps maintain homeostasis (constant internal environment)
NEGATIVES- research initially supported DCT but problems arose such as: rats with lesions to their ventromedial hypothalamus ( satiety centre) still stopped eating, and rats with lesions to the lateral hypothalamus still became hungry
POSITIVE RESEARCH- Lashley= rats were trained to navigate a maze to obtain food. different parts of their brain were lesioned to see the effects on eating behaviour. lesions to lateral hypothalamus made animals stop eating spontaneously and lesions to the ventromedial hypothalamus caused rats to eat in excess. this supports the idea that the hypothalamus is the "eating centre" of the brain. and the lateral hypothalamus being the hunger centre and the ventromedial hypothalamus being the satiety centre
POSITIVE- there has been multiple pieces of research carried out on rats that confirm the theory
set point theory=
solution to DCT to explain long term effects of lesions
suggests everyone has an individual metabolic set point
set point alters depending on several factors like eating and exercise
when people diet leptin levels decrease which causes the hypothalamus to trigger hunger.
set point is higher for obese individuals and lower for underweight individuals
POSITIVE RESEARCH- rats that were obses due to ventromedial hypothalamus lesions were force fed which caused them to become obese. then they were stopped being force fed and they returned to previous body weight- back to their set point
the role of leptin and ghrelin
leptin=
produced by fat cells and associated with the regulation of energy intake and expenditure
ghrelin=
produced by the stomach to increase apetite. concentration of it in theblood falls after each meal then it slowly rises
if calorific storage is high then appetite will decrease. when the fat is used up then leptin levels fall which creates the sensation of hunger.
colemans research on rats
explanations for food preferences
evolutionary explanation for food preferences
talks of natural selection. individuals with genetic variability that help locate sufficient amounts of safe, nutritious foods have a selective advantage.
the pleistocene era (aka Environment of Evolutionary Adaptiveness) is when its believed our food preferences were formed.
during this period, humans lived in small hunter groups and food was scarce so it made sense to evolve preferences such like energy rich foods because they didnt know when their next meal would be available.
it also made sense to evolve food preferences to detect poisoness foods. individuals with these preferences had a survuval advantage and these genes were passed on
sweet taste preference
sweetness associated wit high energy, non-poisoness food
POSITIVE RESEARCH babies facial expressions studied and found they prefer sweeter foods like cake rather than bitter ones like brussel sprouts- suggests innateness. NEGATIVE- subjective
POSITIVE RESEARCH Logue found that the human tongue has specific receptors for detecting sweetnesswhich isnt the case for other tastes detected by non-specific receptors. more receptors for detecting sweetness than other tastes suggesting sweetness is more important. genetic component shaped by evolution.
POS/NEG EVALUATION- Inuit people presented with stwwtness for the first time and accepted it despite never having it before, but Copper Eskimos were disgusted by it- going against the idea that sweet preference is innate.
POS EVALUATION- sweet preference heavily seen throughout animal kingdom. bears endure bee stings to obtain honey
salty taste preference
salt is key for maintaining muscular activity and water balance. sodium chloride is essential for hydration. salt in blood must be at certain level, salt is lost through sweating and kidney action. salt deprivation causes cravings
POSITIVE RESEARCH- Denton found innate preference for salt in many animal species suggesting preference has survival value and is evolutionarily determined.
POSITIVE RESEARCH- found people with sodium deficiency find salt more tasty than related family members
NEGATIVE EVALUATION- individual differences, some neonates prefer it more than others which is puzzling
POSITIVE EVALUATION- deer in highlands lick salt of roads in winter to satisfy cravings despite the high risk associated with this. animals like tigers dont do this because they get sufficient amount from their prey
bitter and sour tastes
indicates presence of poisons. plants produce toxins to discourage ingestion to it is evolutionarily beneficial to be able to detect and dislike such tastes.
humans have around 30 genes that code for bitter taste receptors and humans can detect wide variety of bitter tasting substances
POSITIVE RESEARCH EVALUATION- children and mothers were tested for preferences for sour foods. was found that young children have a much higher preference for sour foods. this makes evolutionary sense because they were less neophobic and more willing to try new foods. greater interest in trying new foods which wouldve had a selective advantage.
POSITIVE RESEARCH EVALUATION- a bitter synthetic compound called PTC was given to humans and found that humans with a PTC taster gene can taste a wider range of bitter, toxic compounds giving an evolutionary survival advantage.
POSITIVE EVALUATION- childrens medicines have to be sweetened else theyll vomit them back up which shows they have the ability to detect and reject such tastes
NEGATIVE EVALUATION- if the ability to detect bitter compounds gives a survival advantage then, in theory, non PTC tasters should have died out, but there is around a 75:25 ratio of tasters to non-tasters. its believed that maybe they can taste another bitter compound
meat eating
not innate for us to eat meat. people on vegetarian diets dont suffer ill-health.
its believed that the use of fires to cook meet was what gave us the ability to eat it because smoking would mean that it could be saved and natural selection wouldve meant that humans more able to digest meat and resist the harmfull pathogens wouldve survived.
advantages of meat= rich in fat so high in energy. available all year round so advantage over seasonal plant foods. correlation has been discussed over meat eating leading to brain growth and thus, improving intelligence but lots of people believe the brain growth was due to needing the intelligence on how to hunt
POSITIVE RESEARCH EVALUATION- primate feeding strategies were compared with brain size, finding evidence that meat eating led directly to larger, more complex brains suggesting that meat eating was evolutionarily favoured.
NEGATIVE EVALUATION- cultural groups noted for their longevity were studied and it was found they were vegetarians- suggesting meat shortens lifespan.
POSITIVE EVALUATION- the fact that meat eating can be dangerous yet most cultures have adopted it suggests that the overall advantages of meat eating outweigh the drawbacks of it. suggests the tendency was shaped by evolutionary forces due to its survival value
neophobia
a dislike of new or unfamiliar foodstuffs. evolutionarily served as a protective function- new foods could be harmful.
however, learning responses couples with innate predisposition to learn certiain food preferences can change the initial neophobic reaction of a new food into a preference.
neophobic reaction diminishes with repeated exposure so infant learns it is safe.
POSITIVE RESEARCH- Birch et al found 2 year olds goven the most exposure to unfamiliar fruits and cheeses reduced their neophobia of the foodstuffs more quickly. suggests that learning new foods arent toxic reduces neophobia- supports idea that neohpobia has adaptive survuval advantage
also found that neophobic reduction generalised to familar vegetables if repeatedly exposed to vegetables but not to unfamilar fruits
POSITIVE EVALUATION- some children appear less neohpobic than others which has adaptive survival advantage- such children would be more willing to eat more unfamiliar foods and almost act as guinea pigs to test out such foodstuffs. if food was non-toxic, behaviour would be imitated by the other neophobic children.
NEGATIVE EVALUATION- if neophobia is related to the risk of toxicity, then we should see more neohpbia towards meat in hotter countries- as meat can go rotten quicker and is therefore dangerous
taste aversion
an innate ability to dislike and avoid certain foodstuffs.
this occurs when someone eats a food and becomes ill, resulting in the avoidance of this food because it is not associated with being ill. effect only requires one experience of illness and the taste aversion is very resistant to extinction. effect still occurs even if the individual knows it isnt the food that made them sick.
it isnt quite the same as classical conditioning because sometimes vomiting can occur many hours after ingestion but the association is still formed which is called biological preparedness. we are primed by evolution to learn through experience to avoid certain foodstuffs that make us ill as this has an adaptive survuval value.
POSITIVE RESEARCH EVALUATION- rats were given sublethal amounts of poison bait balls and found that they devloped a taste aversion
POSITIVE RESEARCH EVALIATION- experiment into biological preparednesss. rats were given a sweet tasting liquid that they usually like which was paired with an injection which made them vomit. when offered the liquid again they declined it because they were biologically predisposed to do so as an adaptive behaviour. However, when they were gien the liquid paired with an electric shock they kept drinking the liquid because they didnt have a biological predisposition to avoid an electric shock.
POSITIVE EVALUATION- dead sheep on farms are laced with lithium chloride to make coyotes etc ill if they feed on them. predators also display submissive behaviour towards living sheep
?EVALUATION- taste aversion demonstrates how learnt behaviour can be underpinned by biological/ genetic influences shaped by evolutionary forces
the role of learning in food preferences
social influences=
the impact of others upon an individuals food preferences.
seen that when baby moves on to solid foods that the mother has a large influence on what baby will eat. aditionally, what mum eats while baby is still in womb has also seen to impact baby's food preferences
flavours that mum has during birth are transmitted to baby via the amniotic sac and also through breastmilk during breastfeeding. this can lead to adult food preferences
operant conditioning also plays a part- when children are given foods as a reward for eating other foods then those foods become preferred. however, if children are given rewards for eating new foodstuffs then the food eaten to obtain the reward becomes less preferred. also, if adults restrict food that is undesirable then that food becomes more desirable.
overall, childrens food preferences resemble the parents because they share the genetic preferences transmitted by evolutionary forces as well as learning parnents food preferences by sharing same environmental influences
biological explanations for AN
psychological explanations for AN
biological explanations for obesity
psychological explanations for obesity