Experimental method (Types of experiment) Flashcards
experimental methods
*Laboratory experiment
*Field experiment
*Natural experiment
*Quasi experiment
non-experimental methods
*Observational techniques
*Self-report techniques (questionnaires & interviews)
*Correlations
*Case studies
Laboratory Experiments
In a laboratory experiment the IV is deliberately manipulated by the experimenter. These investigations usually take place in an environment (not necessarily a laboratory!) that has been specifically designed so that the experimenter can have full control over any extraneous variables which could potentially influence the results. This means that we can see whether the manipulation of the IV is CAUSING the EFFECT seen on the DV. Participants are aware that they are taking part in this type of experiment.
For example, Clifasefi et al (2006) compared mildly intoxicated participants with those who were completely sober. 82% of the intoxicated participants and 46% of the sober participants were not aware that someone dressed in a gorilla suit had slowly walked across the screen while they were watching a video of students throwing a basketball to each other.
Laboratory Experiments strengths
High control over extraneous variables and the IV and DV are carefully operationalised – this leads to greater accuracy (validity) and objectivity in research studies.
Cause and effect can be determined – since extraneous variables are controlled, the only variable responsible for any change in the DV will be the IV.
Lab experiments are easy to replicate – this is due to the high level of control and the use of standardised procedures. It means that the experiment can be repeated to discover if the results are consistent over time.
Laboratory Experiments limitations
Participants’ behaviour may be unnatural – because of the high degree of control it can be difficult to generalise the results to other settings. Participants may behave differently in in an intimidating lab compared to how they would behave in everyday life.
Demand characteristics – participants are aware that they are being tested so they may try to guess what behavior is expected of them and change their behavior.
Possible ethical issues – e.g., deception in order to reduce demand characteristics.
Field Experiments
As in lab experiments, a field experiment involves the IV being deliberately manipulated by the experimenter. However, field experiments take place in a participant’s usual environment (e.g., a school, a workplace, a hospital, on the street). There is some control over extraneous variables although less than in a laboratory experiment. Participants tend not to be aware that they are taking part in this type of experiment.
For example, if we wish to investigate ‘whether people obey authority figures’, we could dress in four different ways, stand outside a railway station, drop a piece of litter on the ground, point to a passer-by and say, “pick that up.” We could dress in (a) everyday clothes, (b) as a milkman, (c) as a soldier, and (d) as a policeman. We could count the number of times passers-by (our participants) followed the instruction to pick our litter up.
Field Experiments strengths
Participants’ behaviour is likely to be natural – because participants are being studied in their usual environments their behaviour is likely to be a genuine reflection of how they would usually behave.
Reduced likelihood of demand characteristics – participants are not usually aware that they are being tested so will be less likely to try to guess what behaviour is expected of them and change their behavior.
Field Experiments limitations
Field experiments are difficult to replicate – this is due to the low level of control. This means it is difficult to repeat the study exactly to see if similar results can be obtained.
Cause and effect is more difficult to determine – since not all extraneous variables are controlled, we cannot truly say that the only variable responsible for any change in the DV will be the IV.
Possible ethical issues – e.g., consent, deception, invasion of privacy.
Natural Experiments
In a natural experiment, the IV has not been deliberately manipulated by the experimenter but instead occurs naturally (it is usually an event) and can be identified by the researcher. Like field experiments, natural experiments take place in the participants’ usual environment. Unlike a field experiment however, there is no control over extraneous variables. Participants tend not to be aware that they are taking part in this type of experiment.
A natural experiment was conducted in St Helena to see whether the introduction of TV would produce an increase in anti-social behaviour (Charlton et al, 2000). The residents of this tiny island received TV for the first time in 1995.
They found no difference between the anti-social behaviour in the inhabitants before TV was introduced and after the introduction of TV. The IV (introduction of TV) was not manipulated by the experimenters; they were just making use of an event which was occurring naturally. Here the first condition represented a control condition and the second represented an experimental condition.
Natural Experiments strengths
Participants’ behaviour is likely to be natural – because participants are being studied in their usual environments their behaviour is likely to be a genuine reflection of how they would usually behave.
Reduced likelihood of demand characteristics – participants are not usually aware that they are being tested so will be less likely to try to guess what behavior is expected of them and change their behaviour.
Allows the investigation of situations not usually possible due to impractical or ethical reasons. For example, where is it not possible to manipulate an IV.
Natural Experiments limitations
These types of experiments are difficult if not impossible to replicate – this is due to the lack level of control. This means it is difficult to see if similar results can be obtained.
Cause and effect cannot be determined – since extraneous variables are not controlled, we cannot say that the only variable responsible for any change in the DV will be the IV.
Possible ethical issues – e.g., consent, deception, invasion of privacy.
Quasi Experiments
As with natural experiments, in a quasi-experiment the IV has not been deliberately manipulated by the experimenter but instead occurs naturally. Here, the IV is a characteristic of the participant – such as gender or age. Unlike natural experiments, quasi experiments can take place in an artificial (lab) situation or in a participant’s usual environment. This means that there may be some control over extraneous variables. It is important to note that in a quasi-experiment, participants cannot be randomly allocated to conditions, as the IV (a characteristic of them) is what has led to them being in that condition.
An example of a quasi-experiment would be if researchers wanted to see if male and female students used different revision techniques for their GCSE exams. The IV (gender) is fixed and cannot be manipulated, but its effect on the DV (use of revision strategies) can be measured by the researcher.
Quasi Experiments strength
Allows the investigation of situations not usually possible due to impractical or ethical reasons. For example, where is it not possible to manipulate an IV such as gender or age.
Quasi Experiments limitation
Cause and effect is more difficult to determine – since only some extraneous variables are controlled, we cannot say that the only variable responsible for any change in the DV will be the IV.
