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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, including EEG, fMRI, and PET scanning.
- Explain how each technique works and what type of data it produces.
- Distinguish between structural and functional imaging methods and explain why this distinction matters for psychological research.
- Evaluate the strengths and limitations of brain imaging techniques using supporting and opposing research evidence in ACAS format.
- Apply knowledge of brain imaging to a real-world case study from the biological perspective.
- Analyse the use of brain imaging in psychology using relevant concept areas: Measurement, Causality, Bias, and Responsibility.
- Discuss the extent to which brain imaging provides a complete explanation of psychological phenomena.
Introduction & Context
Imagine trying to understand how a car engine works without ever being allowed to open the bonnet. For most of human history, that was exactly the situation psychologists and neuroscientists faced when studying the brain. They could observe behaviour, record what people said, and measure reaction times — but the organ responsible for all of it remained hidden, inaccessible, and largely mysterious. The only way to examine a living brain directly was through surgery, which was invasive, risky, and ethically impossible to perform purely for research purposes.
This changed dramatically in the latter half of the twentieth century with the development of non-invasive brain imaging technologies. For the first time, researchers could peer inside a living, thinking, feeling human brain and observe its activity in real time. This opened up entirely new questions: Which brain regions are active when we feel fear? Does the brain of someone who has experienced trauma look different from someone who has not? Can we observe the neural correlates of decision-making, memory, or emotion? Brain imaging did not just give psychology new tools — it gave the field a new language for talking about the relationship between biology and behaviour.
🔍 Analogy Think of the brain as a city at night, seen from a plane. Without any instruments, you can see the city's outline — its general shape and structure — but you cannot tell which districts are busy and which are quiet. A structural brain scan (like an MRI) gives you that city map: the layout, the roads, the buildings. A functional scan (like an fMRI or PET) is like switching on thermal imaging — suddenly you can see which neighbourhoods are lit up with activity, which are dormant, and how traffic flows between them. Both views tell you something important, but neither alone gives you the full picture.
Core Concepts
Before exploring specific techniques, it is worth asking a foundational question: what exactly are we trying to measure when we image the brain? There are two fundamentally different things a researcher might want to know. First, they might want to understand the brain's physical architecture — where different structures are, whether any regions are enlarged or shrunken, whether there is damage or abnormality. Second, they might want to understand the brain's activity — which regions are working harder during a particular task, how neural signals travel, and whether patterns of activity differ between groups of people. This distinction between structure and function is the organising principle behind all brain imaging methods.
📖 Key Definition — Structural vs Functional Brain Imaging Structural imaging refers to techniques that produce detailed images of the physical anatomy of the brain — its size, shape, and the integrity of its tissues — without measuring activity. Functional imaging refers to techniques that measure brain activity, typically by detecting changes in blood flow, electrical signals, or metabolic processes, allowing researchers to infer which regions are active during specific cognitive or emotional states.
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