Dispelling ghostly images with electromagnets

In a study investigating how the brain generates paranormal experiences and psychotic states, researchers used strong electromagnets to alter brain function and found they could reduce the number of times healthy volunteers saw spontaneously experienced false perceptions.

The researchers altered the function of the temporal lobes with a method called transcranial magnetic stimulation or TMS while participants were asked to detect supposedly ‘hidden’ images in what were actually completely random dot patterns.

When compared to a control area at the top of the head, reducing left temporal lobe function significantly reduced the number of false perceptions.

During the procedure, participants were asked to look at a series of quickly presented dot patterns and told to indicate which had images ‘hidden’ within them.

Crucially, they were told not to guess and only to press a button when they genuinely detected a ‘hidden’ image. In actual fact, all the dot patterns were completely random and none contained ‘hidden’ images, so every ‘detect’ response was a false perception of meaningful information.

Just before each dot pattern was presented, the brain was stimulated with a pulse of TMS, either to the left or right temporal lobe, or a control spot at the top of the head known as the vertex.

TMS uses magnetic pulses to safely ‘switch off’ a small area of brain for a several hundred milliseconds.

When compared to the control area, temporarily ‘switching off’ an area on the left temporal lobe significantly reduced the number of false perceptions, suggesting that this brain area is likely to be involved in making meaningful connections, even when there’s no meaning to be found.

Seeing meaningful information in random data is known as ‘apophenia’ and statistically is known as a false positive or a Type I error.

Previous research has shown that this tendency is known to be enhanced in people who report high levels of paranormal experience, and to a greater extent, in people who experience psychosis – the mental state involving delusions and / or hallucinations that is most commonly linked to schizophrenia.

Other evidence suggests that differences in temporal lobe function are common in people diagnosed with schizophrenia.

The paper is published in the May edition of Cortex, but a pre-print is available at the link below if you don’t have access to the journal.

pdf of full-text paper.

Disclaimer: This study is from my own research group

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