Brain switching and the disappearing dots

By Murray Bourne, 28 Jun 2006

Bonneh's Illusion gives a fascinating insight into the way our brains work.

It turns out that our left and right brains switch for control of our consciousness. Where did this realisation this come from? The independent eyes of the sandlance fish move one at a time - indicating that the left brain is in control for a time and then the right brain is in control.


Prof Jack Pettigrew of Queensland University wondered whether human brains also switch between left and right hemispherical control. The Bonneh Illusion test indicates that the human brain certainly does switch.

When you concentrate on one of the fixed dots, the dots disappear among the swirling mass of blue dots. What is happening is that the right hemisphere is more likely to notice finer details whereas the left hemisphere is more aware of the big picture. As the hemispheres switch control, the dots are either important or not important and so appear or disappear.

» Try the Bonneh Illusion test.

But wait, there's more! The speed of brain switching reveals an interesting finding. Mathematicians show slow switching (less than 4 switches in 30 seconds) while dancers and musicians show fast switching (more than 6 switches). This makes sense in that mathematicians need to concentrate on one aspect of a problem for a long time whereas for dancers, small and large picture issues are constantly in play - and need to be 'refreshed' constantly.

My rate was 2 switches in 30 seconds, consistent with my mathematical leanings.

What they didn't talk about in the study was gender differences in brain switching. I would expect that women would have faster switching rates, due to their larger corpus callosum.

For a transcript of the ABC Catalyst item on this fascinating study, see Brain Switch.

See the 2 Comments below.

2 Comments on “Brain switching and the disappearing dots”

  1. MIss Cellany says:

    I am confused by the test, and I find I can't honestly test myself on it because:

    The first time I tried it - I could see the yellow dots ALL the time (they faded now and then to a weaker yellow as blue dots passed over them but they weren't gone entirely).

    But to take the test they're meant to disappear right?

    So I tried again but this time I tried to focus really hard on just one dot and ignore completely the others - this time the other dots disappeared and didn't come back at all.

    So the third time I wanted to be able to count the "switches" so I focused on one dot and then willed myself to see the other dots as and when I wanted - the dots came back whenever I wanted a "wider focus" (without moving my eyes, similar to when you want to "look" at something with your peripheral vision but you don't move your head or eyes, just focus your brain on that spot of your vision).

    Basically, I can't take the test because I can control when I see the dots. so If I want a "fast" switch time, I can make it fast. If I want a "slow" switch time, I can make no switches whatsoever...

    Since I appear to have control over the switch, does this mean I'm untestable?

    by the way, I am female, play 2 instruments, love logic puzzles, paint and draw all the time, and I studied biochemistry at University (so a good mix of right and left brain?).

  2. Murray says:

    @Miss Cellany: Thanks for the interesting response to this! I don't know that I would say you are "untestable", since you've already tested yourself 🙂

    I think it's very interesting you appear to have control over the switches. Total speculation here, but it could be that your brain waves (or eye-brain responses) are either slightly faster or slightly slower than the people who mostly report the disappearance phenomenon.

    I mean something like when watching a movie with helicopters or other propeller driven aircraft. At times, the frame rate of the camera and the rotation of the propeller match up so it appears the propeller is still (albeit blurred). Perhaps that's what's happening in your case.

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