Perceptual rivarly (Part 2)
In my last post I talked about perceptual rivalry and showed you some of Jack Pettigrew’s demonstrations. So, how do we explain what’s going on here? Jack Pettigrew’s theory is that the two hemispheres of our brain are competing for control of interpreting the image; that when we see one image, it’s the left hemisphere, when we see the other, it’s the right. This is called interhemispheric switching. There is already evidence for this - try breathing through your nose while blocking first one nostril and then the other; you’ll find that one is blocked and one is clear (approximately, and assuming you don’t have a cold!) Now, try this every hour - you’ll find that the open nostril will oscillate back and forwards over a few hours. It’s an example of interhemispheric switching - each hemisphere controls one nostril! (Remember that each hemisphere is responsible for the opposite side of your body, e.g., your left hemisphere controls your right hand. ) The nostril switching was apparently known to ancient mystics! An even more amazing example is the Sandlance fish. Each hemisphere of its brain controls an eye, but the eyes always move in alternation, never at the same time. Control is being passed back and forwards between the hemispheres! And you can easily see this for yourself.
Jack’s got some pretty strong evidence to back up his claims for the connection between interhemsipheric switching and rivalry . In his lab (where volunteers, or just the curious, are always welcome!) subjects watch perceptual rivalry demonstrations (similar to, but more complex and controlled than, the ones on the web) and push a button every time their view changes. As soon as they do, he then either pumps one of their ears full of icy water (which has the beautiful technical term “caloric vestibular stimulation”) or applies a sudden magnetic field to one side of their head. (Yep, volunteers always welcome!) The subject then “locks” towards one perception over the other, undoing the switch immediately if need be, and stimulating the other side of the head would lock to the other perception!
What’s even more amazing is that if interhemispheric switching really is occuring, then it must play a part in high level brain functions, such as mood and motivation. And again, this theory holds up - people with bipolar disorder have a much longer “switching times” between the two perceptions than the average. This has been repeatedly demonstrated by experiments. Jack Pettigrew’s theory is that people with bipolar disorder become “locked” into one side of the brain - the left hemisphere is associated with “positive” mood changes, while the right hemisphere with “negative”, corresponding to the manic and depressive mood swings. But can we use this information practically? You bet! In people in the mania phase, who they theorised were locked into the left hemisphere, they injected icy water into the left ear (as mentioned above) and the brain was shocked into stimulating some right hemisphere activity, and the mania was cured! Great quote: “One wonders whether the 50c syringe of cold water will catch on in the clinica”. In a “normal” person, you can even stimulate those moods by doing the same thing - the cold water temporarily “knocks out” one hemisphere, leaving the other in control - put icy water in someone’s left ear and their right hemisphere takes over, leaving them feeling depressed. Pump it in the other ear, and they’re in a fabulous euphoric mood!
This is only a small part of the research that Jack Pettigrew and his group are doing. He’s quite interested in Buddhism: he’s travelled around testing the perceptual rivalry switching time of Buddhist monks and the Dalai Lama and is designing and planning to run experiments to test Buddhist beliefs. Both are with the full support of the Dalai Lama, who actively encourages scientific research into his faith, and has repeatedly said that if anyone can demonstrate scientifically that one of their beliefs are false, then he will change their teachings immediately. A refreshing change!
I’ll write more on Jack Pettigrew in the futre, but to finish, here’s one more selection of my favourite demonstrations - this one is amazing (my favourite!), as is this one and this one.
Joel Says:
That’s so neat! I haven’t tried it yet (no radio clock here in Oxford!) but I definitely will when I get back home. I can’t WAIT to see my housemate’s expression when she hears and/or sees this going on in my room…
Thanks for the tip!
David Moyer Says:
I discuss Jack’s theory in my book, Too Good to be True? Nutrients Quiet the Unquiet Brain - a Four Generation Bipolar Odyssey” and guess what? Left caloric vestibular stimulation works. I discuss Dr Dodson’s case study in my book but can also attest as to its effectiveness because I had used it on my son who was very manic. Within a minute he was back to normal and it lasted 12 hours.
Another wacky effect:
Look at a radio clock, (it needs to be one with bright [preferably green] digits) and blow a rasberry. Compare with when looking at inanimate objects- for example, your hand.
Happy rasberrying! (You rarely have this good an excuse)
Taken Directly from a CSIRO email:
“When your eyes are wobbling back and forth, you only see the digits when they flash on. Since they are only turned on for a fraction of a second, they aren’t blurred out like other objects. Each time the digits flash, they appear to be in a slightly different position. When you look at it, the phi phenomenon makes it look like you are seeing moving digits.”