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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