How Science Works
2. Methodology/How Science Works
For this section you need to be able to:
(a) Describe research methods used to assess witness effectiveness including the laboratory experiment and the field experiment.
(b) Evaluate, including the relative strengths and weaknesses, the research methods listed in (a) above including:
- Their use in criminological psychology
- Reliability, validity and ethical issues
Note: In the examination, students may be asked about the methods used in the applications and asked to describe and evaluate, drawing on other methods both within the application and the five psychological approaches in AS.
Research methods used to study witness effectiveness.
Eyewitness testimony is an account people give of an incident they have witnessed. In criminological psychology, an eyewitness will provide police with a statement about a crime they have witnessed. Psychologists have questioned the effectiveness of witness testimony as many factors can affect a witness including how they are questioned by the police. Therefore, psychologists have carried out research to study the effectiveness of witnesses using a range of research methods. The two main ones are laboratory experiments and field experiments.
Laboratory Experiments
Laboratory experiments used to examine witness effectiveness are conducted in artificial environments where a researcher manipulates the independent variable and measures its effect on the dependent variable. They test a hypothesis that is generated from a theory and then the theory is amended or confirmed according to the results of the experiment. A laboratory experiment is set up rather than occurring naturally and allows psychologists to make statements about cause and effect. One example of a laboratory experiment set up to examine witness effectiveness is by Loftus & Palmer (1974). This is one of the studies in detail which you must know for criminological psychology and you will find a detailed description of this study later on in the notes.
Strengths and weaknesses of using laboratory experiments to study witness effectiveness.
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Strengths
- Reliability refers to the consistency of the findings of research. High reliability is established by using experimental controls and being able to replicate research. Laboratory experiments have high reliability because it is possible to control many factors so that only one (the independent variable) is being studied directly. For example, in Loftus & Palmer’s laboratory experiment of eyewitness testimony she had a high level of control over participant and situational variables and showed participants the same video of a car accident.
- Quantitative data is numerical and potentially very reliable. Quantitative data allows statistical tests to be conducted on results; this means the likelihood of any effects being real or due to chance can be estimated quite accurately. For example, in Loftus & Palmer’s laboratory experiment of eyewitness testimony she collected quantitative data in the form of speed estimates.
- Ethical issues can often be easier to address in a laboratory experiment. Protection of the participants is possible if the procedure involves showing participants videos of crimes or incidents. Participants will be informed of their right to withdraw from the experiment should they find the images upsetting. It is also possible to obtain the participant’s consent since they are aware of the fact they are participating in an experiment.
Weaknesses
- Validity refers to how well a study measures what it is supposed to. Specifically, laboratory experiments of eyewitness testimony lack ecological validity because they are conducted in artificial surroundings that do not recreate the situation experienced by a real witness. For example, in Loftus & Palmer’s laboratory experiment witnesses are prepared to view and recall from video footage. Under these conditions it is unlikely they will experience the same distress as they will be aware that what they are witnessing is staged. Also, the witnesses were not interviewed by the police but rather through the use of a questionnaire.
- Sample size is often a weakness when carrying out laboratory experiments of eyewitness testimony. Due to the high levels of control needed to carry out the laboratory experiment in the same environment this is often done at the expense of a large sample. This may mean that the sample lacks generalisability. Furthermore, samples often consist of students as participants meaning that the population validity is low. For example, Loftus & Palmer used a small sample of 45 students from the university where the research was conducted. One problem with this is that the findings might not be generalisable to the whole population; this is because students may have different motivation when carrying out the study.
- Ethical issues can sometimes be a problem, namely deception and informed consent. In order to improve the validity of the laboratory experiment and to avoid demand characteristics the researcher may choose to deceive the participants. Such deception may result in participants feeling distressed or embarrassed which in turn becomes a protection issue. Furthermore, the use of deception will inevitably mean that the informed consent of participants was not obtained meaning that they were not fully aware of the nature and consequences of the research.
Field Experiments and Field Studies
Field experiments are also used to test witness effectiveness and also have control over the independent variable whilst measuring the dependent variable. However, field experiments are conducted in a more natural setting using real situations. One example of a field experiment is by Yarmey (2004). This is one of the studies in detail which you must know for criminological psychology and you will find a detailed description of this study later on in the notes.
Field studies differ as there is no control over the independent variable and dependent variable. One example of a field study is Yuille and Cutshall (1986) because they collected data using interviews and did not have control over variables. This is one of the studies in detail which you must know for criminological psychology and you will find a detailed description of this study later on in the notes.
Strengths and weaknesses of using field experiments to study witness effectiveness.
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Strengths
- Less demand characteristics are associated with field experiments. There is little chance of the participants working out the aims of the experiment because they are usually unaware that they are taking part in psychological research. This would mean that participants do not alter their behaviour in response to the demands of the situation. For example, in Yarmey’s (2004) field experiment on eyewitness recall and photo identification participants were not aware they were taking part in a study so did not alter their behaviour in response to the situation by paying special attention to the female who approached them.
- Ecological validity refers to whether the task used in the research is something that would be encountered in real life (mundane realism). Field experiments have good ecological validity because participants in the research are essentially experiencing the conditions as a real eye witness. Furthermore, the research takes place in the participant’s natural setting and it is likely that the results will generalise from the experiment to real life. For example, in Yarmey’s study witnesses were approached by female asking for help in a public place which is a realistic environment for this situation to occur. It has mundane realism because it is something that could happen in everyday life.
- Ethical issues such as consent and the right to withdraw may be largely avoided in field experiments. If an incident is staged that a person might experience in their everyday lives, there is less need for consent. Similarly, a right to withdraw may not be a significant issue if participants are likely to encounter the situation in everyday life.
Weaknesses
- Reliability refers to the consistency of the findings of research. High reliability is established by using experimental controls and being able to replicate research. Field experiments have relatively low reliability compared to laboratory experiments because such experiments are hard to replicate due to a lack of control over variables. Extraneous variables such as situational variables may occur in a natural setting and these variables may affect the findings of the experiment leading to inconsistent results and low reliability. For example, in Yarmey’s study there was a lack of control over the situational variables that may have affected witnesses during the incident. The witness may not have been paying attention or may not have been able to offer help therefore spending less time with the female than some other participants.
- Validity of tasks may be low. For example, a line-up that has been set up is not the same as identifying a real-life criminal. It may simply involve guessing.
- Ethical issues may arise when conducting field experiments. For example, protection of the participants must be carefully considered because they will believe the incident they are witnessing is a real-life event. The researcher would need to weigh up the nature of the incident they are intending to stage to make sure it does not cause excessive distress to the participants.