Mori, K., Shinshu University, Japan
A new technique (Manipulation of Overlapping Rivalrous Images by polarizing filters; MORI) has been invented for experimental research in memory distortion of eyewitnesses. In the MORI technique, two different images presented on the same screen can be seen separately by two groups of viewers without noticing that there are two different overlapping images. Therefore, it can artificially create 'conflicts' among eyewitnesses of the same event. Using this experimental technique, six experiments were carried out with eyewitnesses of different group sizes and various sexual groupings. The results showed that (1) although the eyewitnesses observed some rivalrous images they could easily come to an agreement with a short discussion after observing the event; (2) once they reached an agreement, those who changed their minds tended to report the distorted memory a week later, with or without noticing it; (3) there were no sexual differences in tendency of agreement; (4) even those who changed their minds after discussion rated high on the confidence in their reports; (5) the isolated eyewitnesses changed their minds more frequently and unilaterally in accordance with the majority; (6) when they observed the event with a co- observer, they tended to maintain their original reports even after the incompatible discussion; and (7) discussion improved subjects' memory of the events in general.