1.1 Types of experiments

Lab experiments

Conducted in a highly controlled, artificial environment where the researcher deliberately manipulates the IV to measure its effect on the Dependent Variable (DV)

Strengths:

• High control over extraneous and confounding variables.

• High internal validity (confident about cause-and-effect).

• Easy to replicate due to standardized procedures. Limitations:

• Low external (ecological) validity because the artificial setting does not reflect real life.

• Prone to demand characteristics (participants changing their behavior because they know they are being studied)

Field experiments

the researcher manipulates the independent variable (IV) and measures its effect on the dependent variable (DV) in a natural, everyday setting

Strengths:

• High mundane realism + external/ecological validity because behavior happens in a normal environment.

• Lower risk of demand characteristics if participants are unaware they are being studied

Limitations:

• Less control over extraneous and confounding variables.

• Harder to replicate.

• Ethical issues regarding informed consent and invasion of privacy (since participants often do not know they are taking part)

Natural experiments

The researcher takes advantage of a naturally occurring event that manipulates the IV. The researcher does not (and cannot) manipulate the IV themselves

Strengths:

• Allows research into topics that would be unethical or impossible to manipulate experimentally (e.g.a natural disaster).

• High external validity.

Limitations:

• Events happen rarely, limiting opportunities for research.

• Participants cannot be randomly allocated to conditions by the researcher, which can lead to confounding variables

Quasi-experiments

The IV is based on a pre-existing difference between people (e.g., age, gender, ethnicity, or diagnosis of depression). The researcher does not manipulate the IV; it already exists

Strengths:

• investigate variables that can’t otherwise be ethically

• high ecological validity

• Allows comparison between different groups of people

Limitations:

• Participants cannot be randomly allocated to the different conditions, meaning researchers cannot rule out individual confounding variables.

• Causal conclusions are weaker than true lab or field experiments