|Method||Description of Method||Strengths||Weaknesses|
|Laboratory Experiment||· A highly controlled setting
· Artificial setting
· High control over the IV and EVs
· For example, Loftus and Palmer’s study looking at leading questions
|(+) High level of control, researchers are able to control the IV and potential EVs. This is a strength because researchers are able to establish a cause and effect relationship and there is high internal validity.
(+) Due to the high level of control it means that a lab experiment can be replicated in exactly the same way under exactly the same conditions. This is a strength as it means that the reliability of the research can be assessed (i.e. a reliable study will produce the same findings over and over again).
|(-) Low ecological validity. A lab experiment takes place in an unnatural, artificial setting. As a result participants may behave in an unnatural manner. This is a weakness because it means that the experiment may not be measuring real-life behaviour.
(-) Another weakness is that there is a high chance of demand characteristics. For example as the laboratory setting makes participants aware they are taking part in research, this may cause them to change their behaviour in some way. For example, a participant in a memory experiment might deliberately remember less in one experimental condition if they think that is what the experimenter expects them to do to avoid ruining the results. This is a problem because it means that the results do not reflect real-life as they are responding to demand characteristics and not just the independent variable.
|Field Experiment||· Real life setting
· Experimenter can control the IV
· Experimenter doesn’t have control over EVs (e.g. weather etc…)
· For example, research looking at altruistic behaviour had a stooge (actor) stage a collapse in a subway and recorded how many passers-by stopped to help.
|(+) High ecological validity. Due to the fact that a field experiment takes place in a real-life setting, participants are unaware that they are being watched and therefore are more likely to act naturally. This is a strength because it means that the participants behaviour will be reflective of their real-life behaviour.
(+) Another strength is that there is less chance of demand characteristics. For example, because the research consists of a real life task in a natural environment it’s unlikely that participants will change their behaviour in response to demand characteristics. This is positive because it means that the results reflect real-life as they are not responding to demand characteristics, just the independent variable.
|(-) Low degree of control over variables. For example, extraneous variables such as the weather (if a study is taking place outdoors), noise levels or temperature are more difficult to control if the study is taking place outside the laboratory. This is problematic because there is a greater chance of extraneous variables affecting participant’s behaviour which reduces the experiments internal validity and makes a cause and effect relationship difficult to establish.
(-) Difficult to replicate. For example, if a study is taking place outdoors, the weather might change between studies and affect the participants’ behaviour. This is a problem because it reduces the chances of the same results being found time and time again and therefore can reduce the reliability of the experiment.
|Natural Experiment||· Real-life setting
· Experimenter has no control over EVs or the IV
· IV is naturally occurring
· For example, looking at the changes in levels of aggression after the introduction of the television. The introduction of the TV is the natural occurring IV and the DV is the changes in aggression (comparing aggression levels before and after the introduction of the TV).
|The strengths of the natural experiment are exactly the same as the strengths of the field experiment:
(+) High ecological validity due to the fact that the research is taking place in a natural setting and therefore is reflective of real-life natural behaviour.
(+) Low chance of demand characteristics. Because participants do not know that they are taking part in a study they will not change their behaviour and act unnaturally therefore the experiment can be said to be measuring real-life natural behaviour.
|The weaknesses of the natural experiment are exactly the same as the strengths of the field experiment:
(-)Low control over variables. For example, the researcher isn’t able to control EVs and the IV is naturally occurring. This means that a cause and effect relationship cannot be established and there is low internal validity.
(-) Due to the fact that there is no control over variables, a natural experiment cannot be replicated and therefore reliability is difficult to assess for.