Psychology/Learn/What psychology can and cannot tell you
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What psychology can and cannot tell you
The field knows a great deal. It is also routinely claimed to know things it does not. Telling the two apart is the most useful single skill on this platform.
Six things that are well supported
- Behaviour is situational to a far greater degree than intuition suggests. Change the setting, the demand or the audience and the behaviour changes — often more than it changes between two different people in the same setting.
- Observation degrades quickly without structure. Definitions drift, attention fatigues, and memory reconstructs towards expectation. Structure measurably reduces all three.
- Naming an emotion changes its intensity. The effect is modest and reliable, and it is one of the cheapest interventions available.
- Sleep, food, load and predictability affect behaviour and mood substantially. A large share of what gets attributed to character is attributable to conditions.
- Prediction of individual behaviour from traits is weak. Group-level associations rarely support confident statements about one person on one day.
- Feedback and practice with a measure beat insight without one. Understanding why you do something is not the same as changing it.
Six things routinely over-claimed
| The claim | What is actually the case |
|---|---|
| You can read a person’s emotion from their face. | Facial movement is informative about facial movement. Inferring an internal state from it is a judgement with a substantial error rate, and the rate rises across cultures, contexts and individuals. |
| You can detect lying from behavioural cues. | Accuracy in controlled studies sits close to chance for most cues. Confidence in the judgement rises much faster than accuracy does. |
| Learning styles determine how somebody should be taught. | Matching instruction to a self-reported style has not produced reliable gains. Matching it to the task and giving processing time has. |
| A questionnaire score describes who somebody is. | A score describes responses to particular items on a particular day. Its usefulness depends entirely on validation evidence for that population and that purpose. |
| Brain imaging shows what a person is thinking. | Imaging shows correlated signal changes under specific tasks, averaged over many trials and often many people. |
| One striking study has changed the field. | A single study is a candidate, not a conclusion. Ask what happened when others tried to reproduce it. |
The honest position
Psychology is strongest when it describes conditions and weakest when it classifies people. Nearly every over-claim above is the same error: taking something reliable at the level of a group or a situation and applying it confidently to one individual on one occasion.
What this means for how we publish
- We describe conditions and responses, not persons.
- We publish no scored instruments, cut-offs or indicative profiles.
- We state the limits of a resource inside the resource, not in a disclaimer nobody reads.
- Where a claim is contested, we say so rather than choosing the version that reads better.
- See our sourcing and review standard.
Educational scope. Everything published on PMA Science Psychology is provided for education, study and professional documentation. Nothing here is a diagnostic instrument, a psychometric test, or a substitute for assessment, treatment, supervision or emergency care by a qualified professional.
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