Experimental Method
Laboratory Experiments
- A lab experiment is a type of research method in which the researcher is able to exert high levels of control over what happens as part of the experimental process
- The researcher controls the environmental factors, such as noise and temperature (possible extraneous variables) so that the effects of the independent variable (IV) upon the dependent variable (DV) can be clearly observed and measured
- Lab experiments use a standardised procedure to ensure replicability and reliability, 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 is 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 Points
| Strengths | Limitations |
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Cause and effect conclusions are more possible than other methods due to the control the researcher is able to exert |
Demand characteristics may be an issue as participants know they are in a study and so may alter their behaviour which impairs the validity of the study |
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The use of a standardised procedure means that the research is replicable which increases reliability |
This method often lacks ecological validity due to the artificial nature of the procedure |
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High internal validity is achieved as the independent variable may be seen to affect the dependent variable without interference from extraneous variables |
This method often lacks mundane realism meaning the results cannot be generalised to real-world behaviour |
Field Experiments
- A field experiment is a research method which takes place in a natural setting, away from the lab
- The researcher has less control over what happens as part of the experimental process
- The researcher controls the environment to some extent but they have to allow the fact that many extraneous variables are included in field experiments
- Field experiments still involve the implementation of an IV and DV, for example:
- A confederate of the researcher pretends to collapse on a subway train: the IV is whether the victim appears to be drunk or disabled, the DV is the number of people who go to the victim’s aid
- A researcher implements a ‘Kindness’ programme with half of the Year 5 students in a primary school: the IV is whether the students have followed the ‘Kindness’ programme or not, the DV is the score they achieve on a questionnaire about prosocial behaviour after one month
- Field experiments collect quantitative data but there is also more scope for researchers to obtain qualitative data as part of the research process, for example:
- Interviews with passengers who witnessed the ‘victim’ collapsing on the train
- Teachers’ observations of behavioural differences in the ‘Kindness’ programme children across the month of the study
- Any qualitative data collected could be used to comment on the quantitative findings and shed light on the actions of the participants
Evaluation Points
| Strengths | Limitations |
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Likely to have higher ecological validity as it is a real life setting |
Harder to randomly assign participants and so means it is more likely a change could happen due to participant variables, rather than what the researcher is measuring |
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Participants are less likely to show demand characteristics as they are less likely to know what is expected from them and are often in their 'natural' environment |
Harder to control extraneous variables within the experiment, which could change the measurement of the dependent variable |
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High levels of mundane realism, which means the results are more likely to be able to be generalised to real-world behaviours |
Natural Experiments
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- A natural experiment is a research method which does not manipulate the IV, it uses naturally-occurring phenomena, for example:
- Age e.g. an experiment in which digit-span recall is tested between a group of young people compared to a group of older people
- Gender e.g. the performance of girls is compared to the performance of boys in an experiment testing emotional intelligence
- Circumstances e.g. a group of teachers from one school who have received training in empathy are compared to a group of teachers from another school who have not had this training on a task involving correctly identifying emotional states
- The researcher has less control over what happens as part of the experimental process as they cannot randomly allocate participants to condition (the participants are the conditions e.g. either young/old, trained/untrained)
- Natural experiments collect quantitative data
Evaluation Points
| Strengths | Limitations |
| Allow research in areas that controlled experiments could not conduct research, this could be due to ethical or cost reasons | Difficult to say there is a cause and effect relationship as too many variables are unable to be controlled so could effect the outcome |
| High external validity as they are conducted in a natural setting with natural behaviours being exhibited | Lack of reliability as incredibly unlikely to be able to replicate the same situation again to test |
