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

Lab experiments

• A lab experiment is a research method carried out in a controlled, artificial environment, where the researcher directly manipulates the IV and measures its effect on the DV

• Because the setting is artificial rather than the participant's natural environment, the researcher can control environmental factors such as noise and temperature (possible EVs), so any change in the DV can be attributed to the IV

• Lab experiments use a standardised procedure for example:

  • The same number of participants take part in each condition of the IV

  • Each participant is given the same instructions (apart from instructions regarding the task as this will differ per condition as per the IV)

  • The same task/materials are used as far as possible given the IV

  • Participants are given the same amount of time to complete the task per condition and across conditions if the IV allows it

• All variables are kept the same/constant; only the independent variable changes between conditions

• Keeping all variables constant means the DV can be measured exactly using quantitative data

Evaluation of lab experiments

Strengths

• Due to the high control involved, lab experiments go some way towards establishing a cause-effect relationship

• Lab experiments use standardised procedure ensures replicability

Weaknesses

• Demand characteristics may be an issue if participants guess the aim of the study or behave in ways which are self-conscious and unnatural

• Lab experiments lack validity as they usually involve participants performing artificial tasks in artificial environments

Field experiments

• A field experiment is a research method in which the researcher still manipulates the IV, but the study takes place in participants' natural setting, away from the lab

• Because the setting is natural, the researcher has less control over the environment, so more extraneous variables are likely to be present than in a lab experiment

• Field experiments still involve an IV and a DV, for example:

  • A confederate pretends to collapse on a subway train:

    • IV = whether the 'victim' appears drunk or disabled

    • DV = number of people who help

  • A researcher runs a 'Kindness' programme with half the Year 5 students in a school:

    • IV = whether students followed the programme or not

    • DV = their score on a prosocial behaviour questionnaire after one month

• Field experiments mainly collect quantitative data, but there is more scope to collect qualitative data too, for example:

  • interviews with passengers who witnessed the 'victim' collapse

  • teachers' observations of behavioural differences across the month of the Kindness programme

• Qualitative data can help explain or add context to the quantitative findings

Evaluation of field experiments

Strengths

• Field experiments are high in ecological validity as they usually take place in real, natural settings

• Participants often don't know they are being studied, so they are less likely to show demand characteristics

Weaknesses

• Less control means more risk of uncontrolled extraneous variables, which could become confounding variables and threaten internal validity — the researcher's ability to be confident the IV caused the change in the DV

• There are ethical issues if participants are not asked for informed consent or given the right to withdraw, and if the procedure could cause them harm or distress

Natural experiments

• A natural experiment is a research method in which the IV is naturally occurring and not manipulated by the researcher

• The IV would have existed anyway, whether or not the study took place, for example:

  • Age, e.g. comparing digit-span recall in a young group and an older group

  • Gender/sex, e.g. comparing girls' and boys' performance on an emotional intelligence task

  • Circumstances, e.g. comparing teachers who have had empathy training with teachers from another school who haven't

• The researcher has less control, as participants cannot be randomly allocated to conditions as they already belong to one group or the other

  • E.g. already young/old, already trained/untrained

• Natural experiments mainly collect quantitative data

Evaluation of natural experiments

Strengths

• Natural experiments allow researchers to study variables that would be unethical to manipulate, e.g. comparing the cognitive skills of adopted Romanian orphans with non-adopted UK children of the same age

• High in ecological validity, as the IV occurs naturally rather than being artificially staged by the researcher

Weaknesses

• Because participants can't be randomly allocated, groups may differ in ways other than the IV (participant variables)

  • E.g. an 'age' IV might be confounded by differences in health or experience between the groups — making cause and effect hard to establish

• The naturally occurring circumstance may be unique, e.g. a specific institution or event (e.g. Covid), so the exact study is difficult or impossible to replicate