The world shifts to the right when you're sleepy

Posted on June 5, 2014

When you're drowsy, new research shows that what's happening on your left often sounds to you as though it's happening on your right. Perhaps that's why it can be so tricky to land a punch on the alarm clock in the morning!

Corinne Bareham and her team asked 26 healthy volunteers (17 women; all right-handers) to relax in a comfortable reclining chair, to close their eyes, and listen to a series of tones. The tones occurred either on the left or right side of space, some further from the centre than others.

After each tone, the participants pressed a button to indicate whether they thought it had originated on the left or right side of space. While this was going on, the researchers recorded the participants' surface brain activity using EEG (electroencephalography). This provided an objective marker of their sleepiness.

The task may appear easy, but when the participants were sleepy, they mislocated nearly 25 per cent of left-sided tones to the right. This compares to an error rate of under 14 per cent when they were alert. "A participant was 17 times more likely to show a right-ward shift with drowsiness ... than a leftward shift, or no shift," the researchers said. In contrast, the participants were slightly more accurate at locating right-hand tones when sleepy compared with when alert.

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Source material from British Psychological Society