Stress on Eyewitnesses

Deffenbacher, Bornstein, Penrod, and McGorty (2004) conducted a meta-analytic review intending to determine the effects of high levels of stress on memory of eyewitnesses. It was argued that much of the confusion in determining the effect of stress on memory was because many studies do not actually push participants to a high enough stress level. This review excluded any studies that did not elevate participant's stress level to elicit a defensive response or activation mode of attention control. This defensive response as defined by Deffenbacher et al is characterized by a pronounced change in physiological measures of stress. These measures include increased heart rate, blood pressure and muscle tone (2004). Two meta-analysis were conducted in this review. One attempted to determine whether stress impacted the ability of an individual’s facial recognition. Moderator variables were also examined that might impact the results of these studies. The second analysis examined the accuracy of eyewitness recall of details and the impact of stress. Additionally, the effect of other variables which may have influenced detail recall were also examined.

The conclusion of the first analysis was that stress did in fact have a negative effect on eyewitness identification accuracy (Deffenbacher et al., 2004). This is the outcome that was expected, however numerous other variables were discovered to have an impact on whether eyewitness memory was found to be impacted by stress. These variables were; lineup type, research paradigm, presence or absences of a staged crime, and witness age.

Lineup type, meaning either a target present (TP) or target absent (TA) was found to moderate the effect of stress on memory. Target present lineups had a m...

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...hat seen in studies that used other methods of causing stress.

Deffenbacher et al. Produced strong findings that stress did have a negative impact on memory both in terms of identification and ability to recall details. However, only studies that caused a particular kind of stress were examined. Studies that only produced orienting responses in participants were included, instead studies that produced a defensive response were used. Included (2004). Additionally, stress had to be controlled directly by the experimenter naturalistic studies were not included. Finally studies had to prove that stress had actually been induced it could not just be assumed to have occurred.

Works Cited

Deffenbacher, K. A., Bornstein, B. H., Penrod, S. D., & McGorty, E. K. (2004). A meta-analytic review of the effects of high stress on eyewitness memory. Psychology Faculty Publication