Eating behaviour

Overview

Eating behaviour is a central topic in psychology because it perfectly illustrates the debate between biological and psychological explanations of human behaviour. Historically, eating was viewed purely as a survival mechanism driven by physiological needs. However, modern psychology recognises that social, cultural, and cognitive factors play an equally significant role. For examiners, the key to success in this topic is your ability to clearly distinguish between these different types of explanations and to evaluate them using specific research evidence. You will need to understand evolutionary factors, neural and hormonal mechanisms, and apply these to explain conditions like anorexia nervosa and obesity.

Neural and Hormonal Mechanisms

The Hypothalamus

Role: The body's central hunger regulation system, operating on a dual-centre feedback loop.

Key Actions:

• Lateral Hypothalamus (LH): The 'hunger centre'. When stimulated, it triggers the urge to eat.
• Ventromedial Hypothalamus (VMH): The 'satiety centre'. When stimulated, it signals fullness and stops eating.

Specific Knowledge: Research by Anand and Brobeck (1951) showed that lesioning the LH in rats led to aphagia (refusal to eat), while lesioning the VMH led to hyperphagia (overeating and obesity).

Hormones: Ghrelin and Leptin

Role: Chemical messengers that communicate energy status to the hypothalamus.

Key Actions:

• Ghrelin: Secreted by the empty stomach, travels to the brain, and stimulates the LH to increase appetite.
• Leptin: Secreted by adipose (fat) tissue. High levels signal that energy stores are full, stimulating the VMH to suppress appetite.

Specific Knowledge: Mice with a genetic mutation preventing leptin production become severely obese. Injecting them with leptin reverses the obesity (Campfield et al., 1995).

Evolutionary Explanations

Food Preferences

Role: Explains why we naturally prefer certain foods based on ancestral survival environments of scarcity.

Key Actions:

• Preference for sweet/fatty foods: Sweet foods indicate high calories; fatty foods provide dense, long-lasting energy.
• Neophobia: An innate reluctance to consume novel or unfamiliar foods, protecting ancestors from potentially toxic substances.
• Taste Aversion: A biological preparedness to rapidly associate a specific taste with nausea, even after a single pairing and a long delay.

Specific Knowledge: Garcia and Koelling (1966) demonstrated taste aversion in rats, showing that classical conditioning could occur with a significant time delay between the stimulus (taste) and response (illness), challenging traditional behaviourist models.

Psychological Explanations of Eating Disorders

Anorexia Nervosa: Family Systems Theory

Role: Proposes that anorexia develops as a result of dysfunctional family dynamics rather than individual pathology.

Key Actions: Salvador Minuchin identified the concept of enmeshment — families where members are overly involved in each other's lives with poor emotional boundaries. The adolescent may use food restriction as the only way to assert control and establish autonomy.

Obesity: Restraint Theory

Role: A cognitive explanation for obesity focusing on the paradoxical effects of dieting.

Key Actions: Herman and Mack (1975) proposed that chronic dieting (restrained eating) makes individuals hypersensitive to food cues. A minor violation of their strict dietary rules triggers disinhibition (the 'what-the-hell' effect), leading to a complete breakdown of restraint and subsequent binge eating.

Second-Order Concepts

Causation

Examiners expect you to distinguish between biological causes (genes, neurotransmitters like serotonin, hormones) and psychological causes (family dynamics, social learning, cognitive distortions) for eating disorders.

Consequence

The consequence of chronic dieting, according to Restraint Theory, is not weight loss but paradoxical overeating due to disinhibition when cognitive boundaries are breached.

Significance

Understanding the multi-causal nature of eating behaviour is significant because it dictates treatment approaches. If anorexia is biological, drug therapies (e.g., SSRIs) might be used; if it is psychological, family therapy or CBT is required.