Pseudo-Hallucinations: Why Some People See More Vivid Mental Images than Others

upstart writes:

Pseudo-hallucinations: why some people see more vivid mental images than others - test yourself here:

Warning: Do not click the following links if you have photosensitive epilepsy!! If you do not have epilepsy but the Ganzflicker is highly unpleasant for you, you are not obligated to continue.

Consider the statements below. What do they describe? A trip on psychedelics? A dream?

I felt I could reach through the screen to get to another place.

Lasers became entire fans of light sweeping around, and then it felt as if the screen began to expand.

I saw old stone buildings ... like a castle ... I was flying above it.

In reality, they are statements that different people reported after viewing the "Ganzflicker" on their computers - an intense full-screen, red-and-black flicker that anyone can access online and that we use in our experiments. In less than ten minutes, it creates altered states of consciousness, with no lasting effects for the brain. Visual experiences set in almost as soon as you start looking at it.

But our new study, published in Cortex, shows that while some people see castles or fractals in the Ganzflicker, others see nothing. We have come up with a theory of where those individual differences come from.

Like a computer screen, the part of your brain that processes visual information (the visual cortex) has a refresh "button" which helps it sample the environment - taking snapshots of the world in quick succession. In other words, your brain collects sensory information with a certain frequency. Yet you see the world as continuous and dynamic, thanks to your brain's sophisticated ability to fill in the blanks.

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