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IB DP Psychology — Concepts | SL & HL | Paper 1
🎯 Learning Intentions By the end of this note, you will be able to:
- Define determinism, reductionism, and positivism using IB-aligned terminology.
- Explain how determinism shapes the assumptions psychologists make about the causes of behaviour.
- Describe how reductionism operates within different levels of explanation in psychology.
- Explain how positivism underpins the scientific method as applied to psychological research.
- Evaluate the strengths and limitations of each concept using supporting and opposing research evidence in ACAS format.
- Apply determinism, reductionism, and positivism to a real-world case study.
- Discuss the extent to which these three concepts provide a complete and adequate foundation for psychological science.
- Analyse these concepts using relevant concept areas: Bias, Causality, Perspective, and Measurement.
Introduction & Context
Imagine you are watching a friend make a decision — perhaps choosing to eat junk food despite knowing it is unhealthy, or snapping at someone when they are stressed. You might wonder: did they choose to do that, or were they somehow pushed into it by forces beyond their control? This question — whether human behaviour is freely chosen or caused by prior factors — sits at the very heart of psychology as a discipline.
Psychology does not simply describe behaviour; it attempts to explain it scientifically. To do that, psychologists must make certain foundational assumptions about the nature of behaviour and how it can be studied. Three of the most important of these assumptions are determinism, reductionism, and positivism. Together, they form a philosophical backbone that shapes how psychological research is designed, what counts as a valid explanation, and what the limits of that explanation might be.
Understanding these three concepts is not just an academic exercise. They determine what psychologists look for, how they look for it, and what conclusions they are entitled to draw. Critically evaluating them allows us to appreciate both the power and the boundaries of psychological science.
🔍 Analogy — The Clockwork Universe Imagine the universe as a giant clock. Every gear turns because the gear before it turned. Nothing happens by accident — every movement is the inevitable result of the movement that preceded it. If you knew the position of every gear at this moment, you could predict every future position perfectly. Determinism applies this same logic to human behaviour: every thought, feeling, and action is the result of prior causes — biological, cognitive, or social. Reductionism says you can understand the clock by studying its smallest parts. Positivism says the only reliable way to understand the clock is to measure it objectively.
Core Concepts
When psychologists try to explain why someone behaves in a particular way, they are implicitly assuming that the behaviour has a cause. This might seem obvious — of course things have causes — but the philosophical implications run deep. If behaviour is caused, then in principle it should be predictable. And if it is predictable, then the notion of free will becomes complicated.
📖 Key Definition — Determinism Determinism is the philosophical position that all behaviour and mental states are the inevitable result of prior causes — whether biological, environmental, cognitive, or social. According to determinism, given complete knowledge of all prior conditions, behaviour could in principle be predicted with certainty.
Determinism comes in several forms within psychology. Biological