If you’re looking for some unexplainable anxiety, look no further than this TikTok showcasing the Shepard Illusion.
Michael McBride is a content creator who runs the TikTok account idea.soup, which has bite-sized facts and information about all sorts of topics, from an explainer on how air conditioners work to the origin of the word “quarantine.”
McBride’s most popular video, which is at almost 6.5 million views, is likely to give you a headache though.
The video starts out with, “There’s no way this is a loop” and transitions to McBride listening to a series of tones.
“This is an auditory illusion,” McBride writes in the video. “The sound isn’t actually getting higher, but your brain thinks it is, which is why you’re probably thinking…” and then the TikTok loops back to the opening statement, “There’s no way this is a loop.”
When listening to the tones over and over, the TikTok does seem like it’s on a loop and that the tone just keeps getting higher and higher. In reality, the tones are not getting higher, it’s the same sequence of notes, and the illusion can be applied to the tone decreasing in pitch too.
“Will it ever sound high enough to satisfy what my brain wants???? I’ve watched it for too long,” one person commented on the TikTok.
“WHAT THE ACTUAL EFF,” another replied.
“What have you done to my brain???” a third commenter wrote.
Roger Shepard published a paper on the topic in 1967 explaining how and why this happens. Each octave being played is created with tones that can create ambiguity and confusion when listened to in succession. Based on the context of how we’re listening to these tones, our brain hears each repeated tone as being either higher or lower than the one before.
The Shepard Illusion or Shepard Tone is frequently compared to an “auditory barbershop pole” — a famous optical illusion that makes the brain think that the stripes are moving either up or down rather than around the pole.
Our brains’ reaction to the Shepard Illusion or Shepard Tone is utilized by song makers and movie producers all the time. A popular example being the sounds the Batpod makes, the motorcycle featured in Christopher Nolan’s “The Dark Knight” and “The Dark Knight Rises.”
“I used the concept of the Shepard Tone to make the sound appear to continually rise in pitch,” Richard King, the sound designer and supervising sound editor told the Los Angeles Times in 2009. “When played on a keyboard, it gives the illusion of greater and greater speed; the pod appears unstoppable.”
In regards to the comments on McBride’s TikTok about certain listeners feeling anxiety, that’s also true. Since the Shepard illusion is used a lot to drive suspense in movies, songs or video games, some people subconsciously connect that feeling with suspense when hearing it.
If you’re (literally) looking for more illusions, try to figure out what’s going on in this optical illusion.
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