At the same time, real life cases show that although witnesses know the importance of their recall, their testimonies are not entirely accurate. Does this indicate that schemas might not be the only psychological factor that can affect the accuracy of eyewitness testimonies? .
Psychologists have long considered that the accuracy of a testimony is related to the level of emotional tension arousal of the person being interviewed. The fact that witnesses to violent crimes recall less than witnesses to non- violent crimes can be explained through the study of Yerkes and Dodson (1908). The scientists suggested an inverted U-form relationship between the cognitive efficiency and the arousal of an individual. The performance of people would decline when the arousal level increases up to a point called the optimum. Furthermore, an event might become much more stressful with the presence of a weapon. Studies have shown that victims and bystanders tend to pay extra attention to the weapon that is used in a crime, which can later result in an inability to give an accurate recall of the event. People might be able to describe the weapon that is used in a crime, but not the features of the person that is carrying the weapon (Kramer et al 1990). The weapon effect study was firstly introduced by professor Loftus, along with other influential studies on the limitations of eyewitness testimony.
An element that often seems to affect the truthfulness of eyewitness testimony is the post-event information. Loftus (2003) argued that correct information can be lost, drastically changed and replaced by false information. This is explained largely by the leading questions that the witnesses might be asked. Loftus and Palmer (1974) presented the influence of leading questions in an experiment which demonstrated that the language used to question witnesses has an impact on their recollection. The latter point though, has been strongly critiqued by Yuille and Cutshall (1986).
