Mirrors, mirrors on the wall … the ubiquitous multiple reflection error

Participants decided when somebody, Janine, could see their face in a horizontal row of adjacent mirrors mounted flat on the same wall. They saw real mirrors and a shop-dummy representing Janine. Such coplanar mirrors reflect different, non-overlapping areas of a scene. However, almost everybody made an unexpected error: they claimed that Janine would see her face reflected in multiple mirrors simultaneously. They therefore responded as if each mirror showed similar information and thus grossly overestimated how much each mirror revealed. Further studies established that this multiple reflection error also occurred for vertical rows of mirrors and for different areas of a single, large mirror. The error was even common if the participant themselves sat in front of a set of covered-up mirrors and indicated where they would be able to see their own reflection. In the latter case, people often made multiple reflection errors despite having seen all the mirrors uncovered immediately before they responded. People’s gross overestimation of how much of a scene a mirror reflects and their inability to learn to correct this false belief explains why, despite a lifetime’s experience of mirrors, they incorrectly think they will see themselves in all nearby mirrors.

► Adults were asked when somebody can see their face reflected in a set of mirrors.
► Many people wrongly claimed you can see yourself in multiple mirrors simultaneously.
► People often grossly overestimate when your reflection is visible in a mirror.
► Errors occurred even if people saw uncovered mirrors just before doing the task.
► People seem to think that nearby, coplanar mirrors reflect much the same information.