Alas, poor Yorick!

In the late 1800s, Pears Soap started a successful advertising campaign using an optical illusion. Named ‘Yorick’s Skull’ (for the jester who’s skull Hamlet famously holds) the illusion makes use of the effects of an afterimage.

Aside from being a staple in many optical illusions, afterimages are commonly seen in daily life (think of those dark spots in your field of vision after a bright camera flash). Afterimages are a result of our brain adapting to overstimulation. When exposed to a bright or unchanging stimulus for a length of time, the active photoreceptors in our retina become fatigued and lose sensitivity. As a result, when looking away from the stimulus, our retina takes a few seconds to adjust, causing the afterimage.

Some scientists also argue that prolonged exposure to an unchanging stimulus can cause the brain to expect it to remain unchanging. Hence, when it does change, we see the old image for a few seconds.

In the case of Yorick’s Skull, focusing on the ‘x’ in its right eye causes photoreceptors to lose sensitivity as they become fatigued. Additionally, the static nature of the image may cause the brain to believe that the image will not change. Hence, when we abruptly look away from the image, we can clearly see the skull’s afterimage for a few seconds.

(How this helped to sell soap remains ambiguous…)

3 responses to “Alas, poor Yorick!”

  1. Elbert Y. Gong says:

    I like how you explained that the brain makes assumptions over time and becomes desensitized to certain stimuli. Also, I didn’t know that photoreceptors could become “fatigued”. That was pretty interesting.

  2. Carlos Aizenman says:

    It not exactly that photoreceptors become fatigued, but that they adapt to light. That’s why you can still see a light being turned on during daylight. After images are cool!

  3. Brooke Nawrocki says:

    I love after images! It’s really interesting how the brain assumes that the image will not change.

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