Video: Screensaver reveals new test for synaesthesia

Do you hear the dots moving when you watch the video? Then let us know in the comments below.

It sounds like a Zen conundrum: what is the sound of dots moving? Most of us can’t answer that question, but for people with a newly identified form of synaesthesia, hearing such sights is the most natural thing in the world.

Melissa Saenz at Caltech in Pasadena was tipped off when a visitor looked at her screensaver, which made no noise, and said, “Does anyone else hear that?”

She quizzed him and found that his experience had the hallmarks of synaesthesia: a trigger through one sense was giving rise to a sensory experience in another. It was automatic and her visitor had experienced it as far back as he could remember.


To round up a few more test subjects, she passed around the noisy image via email. To her surprise, a few hundred viewers yielded three more of the new synaesthetes.

She showed them a variety of visual stimuli, from moving dots to flashes of light. Depending on the stimulus, people described simple abstract sounds such as tapping, thumping, whirring or whooshing.

Visual Morse

Saenz and collaborator Christof Koch set out to develop a task that would allow synaesthetes to outperform other people if the auditory sensation was real.

Saenz knew that humans are able to judge patterns in time much better using sound than vision, so she developed a simple type of Morse code.

She asked her subjects to either listen to or watch two sequences before saying whether they were identical.

In reality half were the same and half different. Everyone was about 85% accurate on the sound trials, but whereas controls got only 55% of the visual rhythms right, synaesthetes remained steady at 85%. As they later reported, they were helped by being able to hear the flashes as well as see them.

“The choice of task is great,” says Jamie Ward at the University of Sussex in Brighton, UK. “You can’t fake being better.”

He adds that new types of synaesthesia are being uncovered all the time.

Saenz is following up her study with brain imaging and is also eager to recruit new subjects.

Journal reference: Current Biology (DOI: 10.1016/j.cub.2008.06.014)

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