Why It's So Hard to Thread a Needle: Page 2

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Participants in the experiment were shown a computer screen with two different random shapes on coloured backgrounds.

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The shapes momentarily disappeared behind a dark rectangle and when they re-emerged some had changed.

Either the shape or the background colour, or both, had been changed.

Changing the background colour made the participants slower at telling if the shapes were the same or different.

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But, this only happened when the participants' hands were not near the screen.

As soon as their hands were put near the screen, changing the colour made no difference to performance of the task, says Goodhew.

"In near-hand space we found that they didn't use the colour information. It didn't affect their responses at all," she says.

"Given that M cells don't process colour, that's consistent with a pattern of M cell processing."

This finding supports the idea that M cells, rather than P cells used for reading, are involved in processing visual stimuli near the hands.

While the findings have mainly theoretical significance, Goodhew says there are some practical implications.

"It would explain why threading a needle can be so difficult, because the M cells are not good at seeing details near your hands," she says.

Goodhew says the findings also suggest ways to increase our reading efficiency.

"If your hands are close to the text, you will be a little less efficient at that reading than say if you put the book or the tablet on the desk and took your hands away from it," she says.

This article originally appeared on ABC Science Online.

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