Eyewitness Testimony: False Alarms on Biased Instructions?

In two experiments we investigated the effects of biased instructions on the accuracy of eyewitness identification in a field setting in which some of the subjects were unaware of their participation in an experiment. In Experiment 1, 76 students observed a theft and were later asked to identify the perpetrator from a target-absent lineup, receiving either unbiased or biased instructions. One half of the subjects were debriefed prior to the identification procedure. Instructional bias was found to increase the rate of don't-know responses for undebriefed subjects, whereas debriefed subjects were unaffected by type of instructions. In Experiment 2, we investigated whether cultural or methodological factors could account for the results. Using identical instructions, as in Malpass and Devine (1981), 63 students who had or had not been debriefed received either biased or unbiased instructions. The American findings were replicated only for debriefed subjects, indicating an increase in false alarms as a function of biased instructions. The findings demonstrate that witnesses are less susceptible to biased instructions than has been suggested by previous research.