Binocular Rivalry Experiment

Aphantasia Network

Are you aphantasic? Or not quite sure yet? It is impossible for someone to know with absolute certainty what you are experiencing in your mind's eye, but it is possible to get a more objective evaluation for whether you are aphantasic or not. Create a DIY Binocular Rivalry (BR) experiment to test for aphantasia.

To subjectively address the question of whether or not you are aphantasic, psychologists use the Vividness of Visual Imagery Questionnaire (VVIQ), which asks you to rate different mental images to test the strength of the mind’s eye. To objectively address the question, researchers use a technique called Binocular Rivalry (BR).

Here’s how to make a simple DIY BR test at home, and why it works.


When we suspect our hearing may not work properly, it seems obvious that we would go get it tested. When we suspect something is off inside our mind, it isn’t so easy. Without an objective measurement, it is impossible to say for sure what is going on. How can a doctor possibly see what is happening in someone else’s mind to the degree of accuracy needed to make a diagnosis? As far as aphantasia goes, scientists have actually found one way to test whether someone can visualize people and objects in their mind’s eye. The technique is called perceptual priming, and it uses a phenomenon known as binocular rivalry.

When light enters our eyes, it sends information to our brain about what is happening in the world around us. The brain collects visual data from both eyes and essentially overlaps the information to show us one combined image of the world. When both eyes receive completely different sensory information, the brain can get confused. At this point, rather than overlap the images from both eyes, only one image will take dominance over the other, and that is the image that you will see. This is known as binocular rivalry – literally, two eyes competing.

For example, see the image below. If you look at it through glasses where one lens is red and one lens is blue, the red writing (APHANTASIA) will only be seen through one eye, and the blue writing (SCIENCE) through the other. The eyes will then compete as to which word will be seen. Some people will only see ‘aphantasia’ while some people will only see ‘science’.

Interestingly, if you visualize one word (APHANTASIA) or color (RED) in your head before the picture is shown to you, it becomes more likely that that is the picture and colour you will see. This is known as ‘perceptual priming’ – it prepares the brain to see that image. As you can probably guess, perceptual priming doesn’t work for aphantasics – they can’t visualize the word, so their brain won’t be primed, and they won’t be any more likely to see one word than the other.

To test for aphantasia, you can induce binocular rivalry at home and see if there is any correlation between perceptual priming and what you actually perceive. If you do not have aphantasia, you will be able to visualize the word and should find that you are more likely to physically see what you are visualizing in your mind’s eye. If you do have aphantasia, then thinking about the word will not make it any more likely that you will see it.

How to Do the Binocular Rivalry Test at Home

Part One

  1. You will need a pair of red-blue glasses. This will make sure that the red word will only make it through the red lens, and the blue word will only make it through the blue lens. This sends different sensory input to each eye and stimulates binocular rivalry.
  2. Find a picture on the internet (or make one yourself) where two images or words are superimposed over each other. One image should be red and the other should be blue. Whichever word is on top should be adjusted to 50% transparency as with the word SCIENCE in the picture above.
  3. Print the picture on a white piece of paper with no border.
  4. Have a friend set a timer for 120 seconds.
  5. Stabilize your head by resting your chin on something sturdy – a stack of books on your table works perfectly!
  6. Put on the glasses and have your friend start the timer. Have the friend ask you which word you see every ten seconds for 120 seconds, and record your answers. How many times did you see the red word, how many times did you see the blue word, and how many times was it unclear? Record your results.

Part Two

  1. Now, with your eyes closed, try specifically thinking about the red image. Try to imagine it in your mind, if you can.
  2. Have your friend reset the timer for 120 seconds again. Repeat step six while thinking about the red image. Have your friend record your results. Compare results and share in the comments below.

What the Results Mean

Compare the results from part one with the results from part two. If you found that you saw the red image much more frequently than the blue one in part two (7 or 8/10 times is a good indicator), and you saw the red image more often in part two than in part one, then it is unlikely that you have aphantasia. This is because you have primed your brain to see the red image most of the time, a phenomenon that tends not to work on those with aphantasia.

Did you find it difficult, if not impossible, to visualize the red word in your head before step eight? If you couldn’t visualize the word in your mind, your brain was not expecting to see the word in the same way that it would if you were able to visualize it. This means you saw results in part two that were pretty similar to part one. If that is the case, then you probably have aphantasia.

This measurement is a simple test that can often give you an idea as to whether you do or do not have aphantasia, but, like any at-home test, it is not perfect. The more times you do it, the more accurate your results will be.

If you do conduct an experiment, make sure to share you results in the comments below.

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