Eating behaviour

A person eats an unfamiliar shellfish, becomes violently ill hours later, and afterwards cannot bear even the smell of it. Explain this using evolutionary theory.

1. 01Identify the mechanism

   A single pairing of the food's taste with later illness produces a strong, lasting taste aversion.

2. 02Explain the adaptiveness

   Rapidly learning to avoid a food that made us ill prevents repeated poisoning, so it improves survival - an evolved, biologically prepared response.

3. 03Note the specificity

   Garcia showed we readily associate illness with taste (but not with lights or sounds), so the aversion attaches to the food, not the setting.

Result: The lasting aversion is an adaptive, biologically prepared taste aversion that protects against repeated poisoning.

An animal with damage to its ventromedial hypothalamus overeats and becomes obese. Explain this using the dual-centre model.

1. 01Recall the centre's role

   The ventromedial hypothalamus is the satiety centre, which normally signals when to stop eating.

2. 02Apply the damage

   With the satiety centre damaged, the 'stop eating' signal is lost, so the animal keeps eating.

3. 03Explain the outcome

   Continued eating without a satiety signal leads to overeating and obesity - exactly the effect the dual-centre model predicts, supporting the model.

Result: Damage to the satiety centre removes the stop signal, causing overeating - as the dual-centre model predicts.

A study finds abnormal serotonin activity in people with anorexia. Explain why this does not prove serotonin causes the disorder.

1. 01State the finding

   People with anorexia show abnormal serotonin activity compared with controls - a correlation.

2. 02Raise the cause-effect problem

   Because the participants are already severely underweight, the abnormal serotonin could be a result of starvation rather than a cause of the disorder.

3. 03Draw the conclusion

   Correlational, cross-sectional data cannot establish direction, so the finding is consistent with, but does not prove, a serotonin cause; longitudinal or recovery studies would be needed.

Result: The serotonin abnormality may be an effect of starvation rather than a cause, so causation cannot be inferred.

A dangerously underweight person still perceives themselves as 'fat' and believes that eating a normal meal will make them balloon. Explain this using the cognitive explanation.

1. 01Identify the distortion

   Perceiving oneself as fat when severely underweight is a distorted body image; the belief that a meal will cause dramatic weight gain is an irrational, all-or-nothing belief.

2. 02Explain the maintenance

   These distortions make continued restriction seem reasonable and necessary to the person, so the behaviour is maintained despite the danger.

3. 03Add an evaluation point

   The distortions clearly accompany the disorder, but whether they cause it or result from it (and from starvation) is uncertain, which limits the explanation.

Result: Distorted body image and irrational beliefs maintain the restriction, though their causal status is uncertain.

A restrained eater eats a small cake against their diet rules and then continues eating well past the point of fullness. Explain this using the boundary model.

1. 01Locate the diet boundary

   The restrained eater has set a self-imposed diet boundary below their physiological satiety boundary.

2. 02Cross it (disinhibition)

   Eating the cake breaks the diet rule; this disinhibition triggers the 'what-the-hell' effect, so restraint collapses.

3. 03Eat to the satiety boundary

   With restraint gone, the person eats up to their higher physiological satiety boundary, overeating more than an unrestrained eater would.

Result: Crossing the diet boundary disinhibits eating up to the higher satiety boundary, explaining the overeating.