Another thing psychologists have found out about the processes and factors affecting witness testimony is that the presence of a weapon can cause one to be less accurate in their recall. Loftus et al (1987) showed two different groups two different films. In one scene, a customer could be seen holding a gun a restaurant. In the other version, the customer was holding a cheque. In an identity parade, the participants has viewed the clip of the customer holding a cheque were more accurate than those who saw the customer holding a cheque. This shows that the presence of a weapon can cause witnesses to be less accurate.
Conversely, some psychologist have found that it may not be the presence of a weapon, but the unusualness of the situation that can cause witnesses to be less accurate in their recall. The study by Pickel (1986) tested two explanation of the weapon focus effect, threat and unusualness. The participants watched a two minute video of a hair salon. A man walks to the receptionist and she hands him money. The participants were split into five conditions each viewing a version with the man holding something different in his hand. The different objects were , nothing (control), scissors (high threat, low unusualness), a handgun (high threat, high unusualness), a raw chicken (low threat, high unusualness) and a wallet (low threat, low unusualness). After tem minutes, the participants filled out a questionnaire, the firs part was about the receptionist and the second was about the man. They were instructed to describe him, what he was doing, and to identify him in a line up. Accuracy was significantly lower in the unusualness conditions. This suggests that unusualness can have an effect on recall.
Evaluate what psychologists have found out about the processes and factors affecting witness testimony
When studying the processes and factors affecting witness testimony the investigation used to gather evidence may not have ecological validity. The study by Loftus and Palmer (1974) involved showing their participants a video of an accident, there is a lack of immediacy when viewing an accident on video so it is possible that the participants may not be as affected by leading questions of they had actually viewed an accident. This means that the study by Loftus and Palmer may not be generalised to real life. The study by Duncan (1976) also had low ecological validity as it also involved showing the participants a video of a argument. The participants may not have been as affected by the effect of ethnicity had they seen an accident in real life. This means that they study by Duncan cannot be generalised to incidents in real life.
Some psychologists, when studying the processes and factors affecting witness testimony may use an unrepresentative sample. This is true of the study by Loftus and Palmer (1974); the sample consisted of university students. It is likely that university students are not experienced drivers and may generally not have good estimates of speed. This suggests that the experiment may not have been valid as it may have been measuring the participants’ edibility to estimate speed as opposed to effect of leading questions on recall. The study by Duncan (1976) also used an unrepresentative sample. The sample consisted of white American college students. This sample is not representative of Americans or even college students as the sample does not include women or people of other ethnic groups. This suggests that not all peoples’ perception of an event may be affected by the ethnicity of the people involved.
When investigating the processes and factors affecting witness testimony many psychologist use self report measures. In the studies by Duncan (1976) and Pickel (1998) the participants were given questionnaires after seeing a video. Self report measures such as questionnaires can be easily affected by demand characteristics and social desirability. In Pickel’s study, the participants may have thought they were supposed to concentrate on the unusual objects such as the raw chicken and gun meaning that they paid little attention to the man. This makes the experiment invalid as it may have been measuring the participants assumptions about what they thought they were being tested on. In Duncan’s (1976) study, the participants may have thought that the experimenter wanted them to say “playing around” in the white aggressor condition and to say the behaviour was “violent” in the white aggressor condition. The experiment may not have been valid as a result of this.
Some psychologists, when studying the processes and factors affecting witness testimony, may use an independent measures design. This is the case for the study by Loftus and Palmer (1974). The participants were divided into five conditions characterised by a different verb in the critical question, “How fast were the cars going when they smashed/ collided/ bumped/ hit/ contacted?”. This makes it difficult to control for the variables between the participants in each condition. Therefore, the study may have been measuring the differences between the participants on each condition in their ability to estimate speed as opposed to the effect of leading questions. The study by Pickel also used an independent measures design; the participants were in either the nothing condition (control), scissors condition (high threat, low unusualness), handgun condition (high threat, high unusualness), raw chicken condition (low threat, high unusualness) or wallet condition (low threat, low unusualness). The participant were unaware of the conditions that they were not in. This reduced the chances of demand characteristics as the participants cannot mould their answerers based on the other possible objects. This ensures the validity of the experiment.
You are a police officer and you have been given some clear eyewitness accounts of a suspect. Explain how you would use a identikit or an identity parade to help identify to suspect. Give reasons for your answer.
Upon collecting a group of suspects that fit the descriptions given by the eye witnesses the eye witness would then be individually shown images of the possible suspects alone. Showing the participants the images individually would reduce the possibility of social desirability as the participants would not conform to the responses given by the other witness (Asch). The participants would be shown to images of the suspects sequentially as the study by Lindsay and Wells (1985) showed that showing images of suspects sequentially reduces the possibility of false identification. The participants would be given very little encouragement to choose a suspects as, as shown in the study by Wells (2000), even a little bit of encouragement can lead to false identification. This would be a highly effective method of identifying the suspect as the effects of conformity are minimised as is the possibility of false identification.
