Issues and debates: psychology as a science

Features of science

• Empirical evidence gathered by observation and measurement.
• Objectivity: free from researcher bias.
• Hypothesis testing and falsifiability: hypotheses that could be shown to be false.
• Control of variables to establish cause and effect.
• Replicability and peer review.

Evidence that psychology is a science

• Laboratory experiments with controls: Milgram, Asch, Moscovici, Bartlett-style memory experiments.
• Objective measures: brain scans (Raine et al., 1997), EMG startle (Reichel et al., 2014), blood tests (Suzuki et al., 2014).
• RCTs with random allocation and double-blind procedures (DeRubeis et al., 2005).
• Statistical testing with significance levels, and peer review.
• Replication: Burger (2009) replicated Milgram's findings to 150 V.

Evidence against, and the debate

• Unfalsifiable theories: Freud's ideas (Little Hans) rely on interpretation.
• Subjective methods: thematic analysis, case studies, clinical interviews.
• Low reliability of diagnosis (kappa 0.28 for depression in the DSM-5 field trials).
• Human participants react to being studied (demand characteristics), unlike chemicals.
• Replication problems: not all findings repeat.

Judgement: psychology uses scientific methods where possible, but some questions need qualitative methods to understand experience. Many argue it is a science in its methods but not all its theories, and that qualitative research is valuable even if less 'scientific'.

Worked example

Use Reichel et al. (2014) to argue that psychology can be scientific.

1. It used an objective, involuntary measure (EMG startle) rather than opinions.
2. It had a controlled procedure: standardised timing, counterbalanced picture sets, matched control group.
3. It tested hypotheses statistically and was peer reviewed.
4. But self-report ratings conflicted with the physiology, showing subjective data can still matter.

Answer: Objective measures, control and hypothesis testing support scientific status.

Check yourself

1. What does it mean for a theory to be falsifiable?
   • It has already been proven true
   • It could be shown to be wrong by evidence
   • It cannot be tested
   • It was published in a journal
   Show answer

   It could be shown to be wrong by evidence. Popper's criterion of science.

2. Which study used the most objective measure?
   • Freud's case study of Little Hans
   • Becker et al.'s interviews
   • Bartlett's analysis of story recall
   • Suzuki et al. (2014), using blood tests and measured BMI
   Show answer

   Suzuki et al. (2014), using blood tests and measured BMI. Physical measurements are objective.

3. Which is the strongest argument that psychology is not fully scientific?
   • It uses statistics
   • Some theories, such as Freud's, cannot be falsified
   • It carries out RCTs
   • It uses brain scans
   Show answer

   Some theories, such as Freud's, cannot be falsified. Unfalsifiable theories fail a key test of science.

4. Burger (2009) found 70% of participants continued past 150 V, compared with 82.5% in Milgram's equivalent condition. What is the difference in percentage points? Give your answer to 1 decimal place.
   Show answer

   12.5 percentage points. 82.5 - 70 = 12.5.

5. Explain why replication is important if psychology is to be scientific.
   Show answer

   If a study is repeated with the same method and gets the same results, the findings are reliable and less likely to be due to chance or error, which increases their credibility.. Replication tests reliability.

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Sources

• Pearson Edexcel International Advanced Subsidiary/Advanced Level in Psychology specification (issue January 2026)
• Pearson IAL Psychology component guide: WPS04 (Issue 2, November 2024)
• Pearson IAL Psychology summary of studies: WPS04
• Regier et al. (2013), DSM-5 field trials in the United States and Canada, Part II: test-retest reliability of selected categorical diagnoses, American Journal of Psychiatry

Last updated 8 November 2026. Spotted a mistake? Tell us.