Essay: Eyewitness memory

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  • Subject area(s): Criminology essays
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  • Published on: November 14, 2017
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  • Eyewitness memory
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Whenever a crime takes place, eyewitnesses who are present on the scene can help the police or authorities when the crime is being investigated. However, eyewitness memory can be affected by a series of factors.
One of the factors that can affect eyewitness memory is stress. Whenever a person witnesses a violent crime, his response is almost always one that generates a stressful response to the stressor imposed by the crime. This stressful response is the defensive response which is heavily studied by psychophysiologists (e.g., Klorman, Wiesenfeld Weissberg, 1977). This defensive reaction is the physiological response (increased blood pressure, muscle tone and acceleration in heart rate) resulting when attention control is highly dominant (Tucker and Williamson, 1984). The activation mode, which is one of the two neural control systems that regulates a human’s response to the environmental demands, has three important characteristics. These are: (1) a bias against stimulus change, (2) a tonic readiness for action, and (3) processing under tight attention controls. Some of the tasks that elicit the dominance of activation mode include activities which increase cognitive and/or somatic anxiety such as vigilance, escape, avoidance or ‘pressure’ tasks (Deffenbacher, 1994). When assessing the effectiveness of a condition of heightened stress, it should be compared with another condition that is demonstrably lower in stress (or even free from stress), where the arousal mode of attention control is predominant (Tucker and Williamson, 1984). When the activation mode is dominant, there is a notable deceleration of heart rate and lowered blood pressure (Lacey and Laceym 1974). Deffenbacher (1994) concluded that if a task elicits the arousal mode of attention control, the memory will be enhanced for the most important and informative aspect of the stimulus display. On the other hand, if the activity elicits the activation mode of control, memory can be either enhanced or reduced, depending on the amount of cognitive anxiety and physiological activation present.

Another factor that can affect eyewitness memory is age. Younger adults are more likely to make better witnesses than older adults or young children (O’Rourke, Penrod, Cutler, & Stuve, 1989; Valentine, Pickering, & Darling, 2003). Not only are elderly witnesses more prone to poorer memory that comes with poor perception and processing, they may also show certain patterns of false memory (Aizpurua, Garcia-Bajos, & Migueles, 2009).

The viewing conditions also play a part in eyewitness memory. When it comes to face recognition, four factors are important: exposure time, delay, attention and arousal, and weapon focus. The duration a witness has to look at the face of the offender affects their capacity to recognize the same face subsequently (MacLin, et al., 2001). This is often referred to as the exposure/study time. During an investigation it is of utmost importance that, when relying on eyewitness testimony, it is taken under consideration that varying exposure times can have a massive influence on the accuracy of identification and there is always the risk of false identification.

Furthermore, the rate of accuracy can also be influenced by time delay ‘ the time between seeing the offender and identifying him/her. Barkowitz and Brigham (1982) noted that the accuracy of facial recognition decreased after long intervals; the longer the delay, the greater the chances of false identification.

The concentration of mental effort (attention) and the drive to exert mental effort and maintain perception (arousal) are the other two critical factors with regards to viewing conditions. Studying these factors is essential in determining the levels of arousal and attention that are optimal and damaging to the process of face recognition. Peters’ study (cited in MacLin, et al., 2001) demonstrated that higher levels of arousal contribute to lower levels of accurate recognition. Depending on what the state of arousal was and the witness’ reaction to the situation will influence the precision of their memory. These two factors have also been found to be responsible for another factor affecting eyewitness identification: weapon focus. If a weapon is present during the crime, the victim’s attention will automatically focus on the weapon and not on the offender’s face (MacLin, et al., 2001). These four factors, separately and combined, affect the accuracy of eyewitness identification. Should these conditions be present, the eyewitness could have, unknowingly, made a false identification.

Partial disguise is another factor that can influence a witness’ eyewitness memory. Psychologists refer to it as the modification of one’s appearance that could involve: removing a feature (ex: shaving a moustache or beard), adding a feature (ex: wearing piercings or glasses) or else obstructing a feature (ex: wearing a cap to cover the hair). The first two can make it difficult for eyewitnesses’ in the sense that they had viewed that person/offender before a change in his appearance had taken place. During the commission of a crime, a perpetrator wearing a knit cap during a crime would be covering the most important feature that could later be used to identify him or her (Cutler et al., 1985).

Since it is reported that only 49% of American adults have a good night’s sleep every night and nearly 30% report daytime sleepiness at least 3 days a week(National Sleep Foundation, 2005) , eyewitnesses can vary in the amount of sleep they have before witnessing the crime, the quality of their previous sleep and their sleepiness at that particular time. The correlation between the duration and the quality of sleep are often low or non-significant because different people vary in how deeply they sleep (Liu & Zhou, 2002). The impact that the sleep quality of the previous night has on episodic memory is not fully understood, with certain studies suggesting that reduction in sleep quality harms episodic memory whilst other studies report no effect (Fulda & Schulz, 2001).

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