Pareidolia and clinical reasoning: the pattern awakens

A 20-year-old woman presented to our emergency department after a cliff-jumping adventure went awry. The ultrasound of the aorta was benign, but a “Darth Vader” sign found off the reflection of the spine was no Jedi mind trick (Figure 1). The ability to detect an aneurysm is insignificant next to the power of the Force!

Figure 1:

The Darth Vader sign.

Pareidolia is a phenomenon of recognizing patterns, shapes and familiar objects — often faces — where they do not actually exist.¹ There are several well-known examples in popular culture, including most recently a perception of Vladimir Putin’s resemblance in a flock of birds, the image of Jesus on toast or the “Face on Mars” captured by the Viking 1 orbiter. Examples achieving popular notoriety are found in medicine as well, particularly with diagnostic imaging.

Pareidolia is recognized in humans as young as eight months old.² Compared with other types of illusion, pareidolia is unique in how the illusion often becomes more intense with increased attention to it. Similar neural processes trigger pareidolic illusions and visual hallucinations, which has led to speculation that pareidolia represents a susceptibility to visual hallucinations.¹ Conversely, other studies have shown that the right temporal lobe discriminates between real and illusory faces but is highly suggestible, consistent with a more benign prognosis.³

Could there be more to pareidolia than sheer entertainment value? Simply put, pareidolia is perceiving a meaningful pattern in meaningless noise. In medicine, we learn to detect illness patterns in the noise of nonspecific signs and symptoms.