Pain: types and theories of pain

Psychology A2 · Health Psychology. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.

Test this topic free All Psychology A2 topics

The idea

Pain is useful. It warns of tissue damage, makes us pull away, and makes us rest so that the body can heal. Acute pain is short-term and fades as the injury heals. Chronic pain lasts for months, often after healing is complete, and psychological factors play a large part in it.

Two theories explain pain. Specificity theory says special pain receptors send signals along a direct pathway to a pain centre in the brain, so more damage means more pain. Gate control theory (Melzack and Wall) says a gate in the spinal cord can open or close, so thoughts, emotion and attention change how much pain is felt.

Phantom limb pain, felt in an amputated limb, supports the second theory.

Rules to remember

Functions of pain: warning of damage, protective withdrawal, rest and healing.
Acute pain: short-term, linked to injury. Chronic pain: continues beyond the normal healing time.
Specificity theory: specific receptors → direct pathway → brain. It is biological and reductionist.
Gate control theory: small nerve fibres open the gate, large fibres close it, and messages from the brain can also close it.
Phantom limb pain: pain felt in a limb that is no longer there, so it cannot come from receptors in that limb.
Mirror treatment: the patient watches the reflection of the intact limb moving, so the brain 'sees' the missing limb move.
MacLachlan et al. (2004): case study of one man with a leg amputation; mirror treatment reduced his phantom pain and gave him more control over the phantom limb.

Common mistake

Students mix up the fibres. Small fibres carry the pain signal and open the gate; large fibres (touch, rubbing) close it. Remember that rubbing helps, and rubbing is touch.

Worked example

A boy burns his finger and holds it under his other hand, pressing gently. The pain eases. A week later it hurts more when he is bored and alone. Which theory explains both observations?

Pressing is touch, which stimulates large fibres. Gate control theory says these close the gate, so less pain signal reaches the brain.
Boredom means more attention on the finger. Gate control theory says messages from the brain can open or close the gate.
Specificity theory cannot explain either change, because the damage to the finger is the same each time.

Answer: Gate control theory, because it includes both touch fibres and psychological factors.

Ask about this

Type what you are stuck on. The helper finds the explanation, worked examples and the notes to read, free and instant.

Keep going

← Adherence to medical advice: improving adherence Pain: measuring pain →Take a Psychology A2 test