Experiments: Types of Experiment (OCR GCSE Psychology): Revision Note

A laboratory experiment is carried out in a controlled environment where the researcher directly manipulates the IV

The researcher can control extraneous variables such as noise, temperature, and lighting to ensure the IV is the only variable affecting the DV

A standardised procedure is used so that all participants experience the same conditions (except for the IV), e.g.

• equal numbers of participants in each condition

• the same instructions given to all participants

• the same materials and timings used across conditions

High control of variables helps establish cause and effect

Standardised procedures make results replicable and reliable

Objectivity is increased because researcher influence is minimised

Low ecological validity — the artificial environment doesn’t reflect real life

Demand characteristics — participants may change their behaviour if they guess the study’s aim, affecting validity

A field experiment takes place in a natural environment (e.g. a classroom, park, or workplace) rather than an artificial controlled environment

The environment is realistic, so participants may behave more naturally

The researcher still manipulates the IV, but there is less control over extraneous variables

E.g., a researcher runs a Kindness Programme in a school

• IV: Whether students participate in the kindness programme or not

• DV: Scores on a questionnaire measuring prosocial behaviour after one month

Researchers might also gather qualitative data (e.g. interviews with teachers or observations of student behaviour) to support their quantitative results

Higher ecological validity than laboratory experiments, as the setting is natural

Less chance of demand characteristics due to the realistic and natural setting, improving validity

Less control over extraneous variables compared to laboratory experiments lowers validity

Possible ethical issues, as participants might not give informed consent if they don't know they are part of a study

In a natural experiment, the IV is not manipulated by the researcher — it occurs naturally

• The researcher measures the effect of this naturally occurring IV on the DV

Participants cannot be randomly assigned to conditions, as they are often defined by the IV itself (e.g. age, gender, or life circumstance)

Examples include:

• comparing memory span between young and older adults.

• comparing emotional intelligence between boys and girls.

• comparing people with depression and those without

Allows researchers to study variables that would be unethical or impossible to manipulate (e.g., trauma, gender, adoption)

Often have good ecological validity, as they study real-world differences that occur naturally

Cause and effect are difficult to establish because variables are not directly controlled

Replication is hard — naturally occurring variables (e.g., age, gender, life events) cannot be repeated or recreated