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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:
- Describe the key brain imaging techniques used in psychological research: EEG, fMRI, and PET scanning.
- Explain how each technique works and what type of information it provides about brain activity or structure.
- Distinguish between structural and functional brain imaging methods.
- Evaluate research evidence that uses brain imaging techniques, using supporting and opposing studies in ACAS format.
- Apply knowledge of brain imaging to a real-world case study from the biological perspective.
- Analyse the strengths and limitations of brain imaging research using relevant concept areas: Measurement, Causality, Bias, and Responsibility.
- Discuss the extent to which brain imaging techniques provide valid and reliable evidence for understanding human behaviour.
Introduction & Context
Imagine you want to understand how a city works — its traffic patterns, which districts are busiest at different times of day, and how different neighbourhoods are connected. You could interview residents, but that only tells you what people consciously notice. Alternatively, you could fly overhead and photograph the city from above, watching the lights, the movement, the activity in real time. This is, in essence, what brain imaging allows psychologists to do: observe the living, working brain without ever opening it up.
For most of human history, our understanding of the brain came from two sources — post-mortem dissection and the observation of people with brain injuries. Both approaches were limited. Dissection told us about structure but nothing about function during life. Injury studies, like the famous case of Phineas Gage, revealed that specific brain regions were linked to specific behaviours, but these were accidents of nature, not controlled investigations. The development of brain imaging technology in the twentieth century transformed psychology by allowing researchers to observe brain activity in living, conscious participants — and to link what the brain is doing to what a person is thinking, feeling, or experiencing.
🔍 Analogy — The City at Night Think of the brain as a city. An EEG is like listening to the hum of the city from outside — you can hear the rhythm and energy, but you cannot pinpoint exactly where the noise is coming from. An fMRI is like a satellite image that shows which districts are lit up and active at any given moment. A PET scan is like tracking where the city's fuel supply is being consumed — the busier the district, the more fuel it burns. Each method gives you a different kind of information, and each has its own blind spots.
Core Concepts
Before exploring each technique individually, it is worth understanding a fundamental distinction in brain imaging: the difference between structural and functional imaging. Some techniques show us what the brain looks like — its anatomy, the size and shape of different regions, and whether any damage is present. Others show us what the brain is doing — which regions are active during a particular task, emotion, or experience. This distinction matters because psychology is ultimately interested in behaviour and mental processes, not just anatomy.
📖 Key Definition — Structural vs Functional Brain Imaging Structural imaging refers to techniques that produce detailed images of the brain's physical anatomy, revealing the size, shape, and integrity of brain regions. Functional imaging refers to techniques that measure brain activity — typically by detecting changes in blood flow, oxygen use, or metabolic activity — to identify which regions are active during specific cognitive or behavioural tasks.
With this distinction in mind, we can now examine the three most commonly referenced brain imaging