Surreptitiously projecting different movies to two subsets of viewers.

A new technique (manipulation of overlapping rivalrous images by polarizing filters, or MORI) has been invented for presenting on the same screen two different images that can be seen separately by two groups of viewers without their noticing the overlap. It can easily create desired artificial conflicts among viewers. Two perpendicular polarizing filters provide separate invisible channels from dual video projectors to two groups of viewers on a single screen. The basic principle of the presentation technique, details of the apparatus, and limitations are introduced. As an example of the application of this technique, an eyewitness experiment is briefly reported. The results of experiments conducted by the author and colleagues provide evidence of the effectiveness of this technique with various projectors, video materials, group sizes, and ages of participants.