“Magic mirror in my hand, who is the fairest in the land?” Grimm and Grimm (1812) were among the first to note that mirrors do not always provide the perceiver with the desired or expected result. Two centuries later, our methodologies have become vastly more sophisticated but researchers are still fascinated by how people process information in mirrors.

Although we spend much of our lives surrounded by mirrors, it turns out that mirrors are perceptually quite a bit more interesting than first meets the eye.

Some unexpected features of an everyday object

Here is a simple question: will an object in a mirror appear smaller if it is further from the mirror? Most people think the answer is “yes.” In reality, however, what matters is the distance between the perceiver and the object, not the distance between the object and the mirror.

Not convinced? Here is a two-minute YouTube video that makes the point. Or you can perform the experiment yourself: Mark the projection of your chin and eyebrows on a mirror in front of you (lipstick will do the trick nicely) and then walk away from the mirror. Does your face get smaller? Or do chin and eyebrows stay exactly where they are, aligned with the marks on the mirror?

Your intuition may be quite wrong—mine certainly was.

From erroneous intuitions to neglectful perception

Psychonomics researchers Preeti Sareen, Krista Ehinger, and Jeremy Wolfe recently reported a study in the Psychonomics Bulletin & Review shed further light on the question whether an object reflected in a mirror is perceived differently from an object that is viewed directly.

Sareen and colleagues were interested in whether the “unreality of the looking-glass world [is] reflected in the way that we interact with pictures that do and do not contain reflected objects?” In their first experiment, observers were shown pictures of indoor scenes and were asked to label “everything they saw.” A subset of images contained a mirror that reflected some of the objects, as shown in the figure below.

For example, the hairdryer in the above figure was “visible” both in the room (i.e., nonreflected) and via the mirror (reflected). The results are also summarized in the above figure: Each orange dot refers to one observer who labeled the marked object—so most people labeled the hairdryer in the room, but only a few people labeled the very same hairdryer when it appeared in the mirror. Even when an object was onlyvisible in the mirror, such as the doorknob, relatively few people would report its presence–it is as if it was somehow less ‘real’ in the mirror.

In a second experiment, Sareen and colleagues used a change-detection task. In a change-detection task, observers are shown two stimuli in short succession, and the observer’s task is to decide if the two arrays are identical or whether one item has been changed between presentations. In this particular variant, the two stimuli were flickering back and forth rapidly, and people pressed a button to indicate that they had detected a change. Then they had to click on the object that had been changing. As shown in the figure below, the change could occur in an object that was visible in the mirror and in the room (panel a). Alternatively, the critical object might be visible only in the mirror or only in the room (panel b).  (The figure identifies the changed object with a green circle, but this was not visible to participants.)

The results were clear. It took significantly longer to find the change when it took place in the mirror. This reflection deficit occurred regardless of whether the changing object was visible in the mirror and the room, or in the mirror only.

The two experiments show that people appear to “discount” reflected objects when they experience a scene. It is as though people largely ignore mirrors, even if the objects they reveal are unique or equivalent in size to those that are seen without reflection.

Mirrors are everyday objects, and from an early age we hold the intuitive belief that we understand reflections. I, for one, didn’t think that writing a post about research involving mirrors would surprise me sufficiently to conduct an experiment involving lipstick marks on a mirror.

All that notwithstanding, mirrors can be extremely powerful tools, not only for stepmothers but also in the hands of experts, such as famous 17th-century painters: There is strong circumstantial evidence that the Dutch master Johannes Vermeer used a clever arrangement of mirrors to help him paint some of his masterpieces.

Clever enough, apparently, to permit a 21st-century replication and capture it on film.