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IB DP Psychology — Biological Approach | SL & HL | Paper 1
🎯 Learning Intentions By the end of this note, you will be able to:
- Define localization of function and cortical localization using IB-aligned terminology.
- Explain how specific brain regions are associated with distinct psychological and behavioural functions.
- Describe the role of key brain structures — including Broca's area, Wernicke's area, and the prefrontal cortex — in behaviour.
- Evaluate research evidence for localization of function using supporting and opposing studies in ACAS format.
- Apply localization concepts to a real-world case study from the biological perspective.
- Discuss the extent to which localization provides a complete explanation of brain-behaviour relationships.
- Analyse localization research using relevant concept areas: Causality, Perspective, Bias, and Measurement.
Introduction & Context
Imagine you are listening to a friend tell a story. You understand every word, you can picture the events they describe, and you respond with appropriate emotion. Now imagine that a stroke damages a small region of your brain — and suddenly, although you can still hear sounds perfectly well, words become meaningless noise. You know you want to speak, but the right words simply will not come. What does this tell us about how the brain is organised?
For centuries, philosophers and scientists debated whether the brain operates as a unified whole or whether different regions are responsible for different functions. The discovery that damage to specific, small areas of the brain produces very specific losses — in language, memory, movement, or personality — provided some of the most compelling early evidence that the brain is not a homogeneous organ. Instead, it appears to be organised into specialised regions, each contributing to particular aspects of thought and behaviour.
This idea — that specific psychological and behavioural functions are governed by identifiable regions of the brain — is one of the foundational principles of the biological approach in psychology. Understanding it requires us to look carefully at both the evidence that supports it and the evidence that complicates it.
🔌 Analogy — The Office Building Think of the brain as a large office building. Each floor and each department handles a specific type of work: the accounts department processes numbers, the communications team handles language, and the executive suite makes high-level decisions. If the communications team's office is damaged by a fire, the building still stands — but outgoing messages become garbled or impossible. This is analogous to localization: specific regions handle specific functions, and damage to those regions produces predictable, specific deficits.
Core Concepts
When neuroscientists began systematically studying patients with brain injuries in the nineteenth century, they noticed a striking pattern: the nature of a patient's behavioural deficit seemed to depend not on how much brain tissue was damaged, but on precisely where the damage occurred. A patient with an injury to the back of the brain might lose vision; one with damage to the left side of the frontal lobe might lose the ability to produce fluent speech. This pattern of specific deficits following specific lesions gave rise to the concept we now call localization of function.
📖 Key Definition — Localization of Function Localization of function is the principle that specific areas of the brain are responsible for specific psychological and behavioural functions. Damage to a particular brain region produces predictable and