Tuesday, 3 June 2014

The world shifts to the right when you're sleepy

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.

The finding that tiredness triggers a shift in attention to the right-side of space is not new - researchers have shown this before. However, past demonstrations of the phenomenon have used visual stimuli. This study is novel because of its use of auditory tones and because of the highly accurate measurements of participants' alertness.

Research on this topic has clinical relevance. The drowsiness-induced attentional shift towards the right side of space is similar to a phenomenon known as "spatial neglect" that's observed in patients who have suffered right-hemisphere brain damage. People with left-sided brain damage show the opposite pattern - they tend to ignore the right-hand side of space. However, right-hemisphere brain damage leads to more prolonged and profound spatial neglect than left-sided damage, and this new study offers a clue as to why.

One explanation for spatial neglect following left or right-sided brain damage is that the two hemispheres of the brain are usually in competition, so that when one is damaged, balance is lost, and attention is skewed towards the same side of space as the brain damage. However, people with right-sided brain damage suffer twice, because damage to the right hemisphere is known to induce sleepiness, which - as this study shows - also leads to a skewing of attention to the right side of space.

In the researchers' words, patients with right-hemisphere damage are "doubly compromised" - by the loss of hemispheric balance, and by the effects of drowsiness. The good news is that this insight offers an avenue for treating patients with right-sided brain damage. "The results here confirm that the maintenance of alertness should be ...[an] important therapeutic target," the researchers said.

  ResearchBlogging.orgBareham, C., Manly, T., Pustovaya, O., Scott, S., & Bekinschtein, T. (2014). Losing the left side of the world: Rightward shift in human spatial attention with sleep onset Scientific Reports, 4 DOI: 10.1038/srep05092

--further reading--
Hemispheric bias shifts with tiredness
Space is compressed by a fast turn of your head
Novelty seekers are biased to the right

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.


  1. Yuzhou Huang1:02 pm

    I'm wondering how the initial ratings for the boys and girls were given. If the girls were evaluated on their competition versus only other girls then would the ratings still be accurate? If the ratings were given by compartmentalised girlvgirl and boyvboy data, that wouldn't create a standardised rating. The difference in results would only be a difference in the average skill between boys and girls. Also since boys and girls develop at different rates, the test would do well to compare older boys and girls. However the idea that women naturally feel pressure against men could still have merit if you found girls and boys of similar skills, though that seems impossible if you rate their skills in separate tournaments. Also don't boys feel similar pressure when facing a girl to live up to stereotypes? How about you rate them together when boys and girls compete together through double blind experiments then conduct the same experiment having them play together knowing each other's genders. This experiment seems rather poorly thought out and proves very little.

  2. Hallie Jaeger2:15 pm

    Great post! Had an earworm this morning so I looked it up and linked your blog to my SEOT post here http://seotinc.com

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  4. Eva Lee (李綺華)3:47 pm

    What about left-handers? Does this study replicate results with them? Numbers/ tested subjects seem statistically invalid.

  5. Tristan Bekinschtein10:36 pm

    Why does "Numbers/ tested subjects seem statistically invalid"? Could you justify/elaborate?

  6. Yeah,I totally don't understand the numbers. You had 17 women. All of them were right handed. You had 26 participants. Was the data from the other nine thrown out? were they all men? Were they right handed, left handed or ambidextrous? Wht woukd you give us that information but not the rest?

  7. Of the 26 participants, all were right handed, 17 were women

  8. Eva Lee (李綺華)4:36 pm

    9 men 17 women seems a bit unequal but what really bothers me is that they were all right handed and the test involves pushing a button, left or right. It makes sense that as they are tired, they will push with their dominant hand on the closest button or on the dominant side regardless of the aural input. I'd like to see left handed people in the study. Do the results still replicate? Until then, I feel the conclusion would be invalid.

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  10. I think you have to read the paper again along with the supp info, all the responses to your criticisms are actually there (except the lefties). But I respond to you point by point anyway, there is a single subject graph showing that 21 of 26 participants showed the bias, and stats for that. those not showing the bias were 2 men and three women, so no much problem in that, besides we have a higher sample of this and replicates beautifully. The test involves pushing two button, some pushed with the left hand, some with the right and some with both hands. Again, no differences there, it is unlikely that it is a hand performing-the-task thing. If fact they mislocate sounds on the left saying they come from the right side of space, regardless of gender o hand used to push the button. And the effect is there no matter how you define drowsiness (by EEG, by sleep scale, by RTs). It is a very strong effect! The point is that there is a bias on these subjects. Yes there are all right handers and handedness is a factor that we report in the paper coming out soon (is under review). But regardless of that the effect is there and it is likely that your spatial attention representation shifts even if you still consider the results invalid. IN fact I do not think you can call them invalid, you are entitled to remain unconvinced but the experimental design are valid, the data clear and sound and the results convergent. So maybe you mean that our conclusions are invalid. Last point, all your concerns were raised by reviewers last year in a more elegant manner and answered with new analyses also in a more elegant manner!

  11. Eva Lee (李綺華)11:24 pm

    Of course, if I were writing a formal peer review, my response might have been more elegant; however, this was informal commentary based solely on the information presented in the article and not on the paper still under review, which I obviously have yet to read. As my points were raised by others who have read this paper, I feel that, whether elegantly stated or not, they were still valid. You are, of course, free to disagree.

  12. Given that probably more than 90% of the chess players are male, even online, most girls have to play mostly against boys, even if they may skew the odds of playing against girls by participating in eventual girl-only tournaments (if such thing even exists; AFAIK the standard there's a single tournament, even though different prize/categories for females; the "1st" female can be the 20th player in the overall dispute, the 2nd female the 40th, and so on, but they'd be awarded prizes in the female category and have "weakened" titles, like "women chessmaster", which perhaps would be the rating-equivalent of a male "international master" or whatever).

    Even if such girls-only tournaments exist, the effect may not be so significant due to the own design of the ratings system. By extension, any "pocket" of weak players, playing mostly against themselves, anywhere in the world would have inflated ratings among their top players, and I don't think that happens to a huge degree. That would probably present itself in things like discrepant country-level ratings and worldwide ratings. Weaker countries would have player whose ratings skyrocket to the top, only to stop/fall from the sky when they compete on international disputes. I don't have the impression that anything like that happens, even though I'm not an avid follower of the game.

  13. Wrong, as the study explained in detail.

  14. Does it really make sense? The fact that men are "on average better in chess" has any higher bearing on individual ratings?

    Would it "reproduce" if you took a huge group of only-male chess players, separated 1/10 of them randomly, but adding up to a lower average? The best of this below average group would be predicted to perform worse than expected without this random separation? That the group would score lower is no surprise; but it's not a "team", so to me it seems to me like saying that all of a sudden Kasparov have higher odds of scoring unexpectedly bad if he happens to be wearing the same color of shirt that I would be wearing on a given day.

    I may be missing something here, but I don't think so.

  15. Addendum: it doesn't even apply only to "the best" of the low-average group, even the "just average", or even the worse. I don't think they would suddenly be expected to perform worse than they would if they hadn't been randomly assigned into a group.

    A good thing is that to "empirically" test this idea one doesn't even need new disputes, one could just do random delineations of a small all-male group with similarly below-average ratings with past games, and find the same finding with this post-factum semi-random assignment.

  16. "Essentially they took measures of chess performance prior to a tournament and from these generated 'expected performance' in the tournament."

    Which is logical and convenient since chess ratings are more or less a system designed to give "expected performance", and perhaps it works better than anything comparable elsewhere, or in other games/sports.

    "The authors phrase this as 'girls perform worse against male opponents', without acknowledging that this is the same as saying girls perform worse overall."

    But the study isn't about "girls overall", but individual girls performing worse than what would be expected from their ratings. On girl-vs-girl matches, it was supposedly just as expected from ratings.

    The would then have only been "worse overall" in a significant sense if both girls, when playing against girls in a tournament, would *both* play worse than expected, but proportionally, unlike when it's girls-vs-boys. So even then the finding would be preserved. But I'm afraid the notion doesn't make sense since the supposedly inflated rating would have been produced within tournaments to begin with, including matches against other girls. Doesn't seem to add up to me.

    That possibility, of proportional/mutual decline in performance can be analysed with computers/chess engines, though. I'd be even more surprised with that than I'd be with the "regression to the mean" explanation.

  17. Why is that it would be a problem that women are victims of stereotype threat? Is the effect known to affect only men?


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  22. I often have songs in my head whose lyrics reflect a recent occurrence or preoccupation. I'm an amateur musician and have noticed that it's the fast tempo and exciting big band numbers that replay in my head when I'm trying to get to sleep, not the gentle ballads. Also our musical director won't let us play certain swing pieces because they trigger earworms that would prevent him sleeping.

  23. I have had earworms now for 2 years. EVERY single morning I am awakened by a different song for the most part. Sometimes it is the same song for a week but that is rare. I don't have an alarm clock because like magic (only not as fun)the music in my head slowly brings me to life each day. There has not been a day it has not happened in 2 years and it really bothers me although I have LEARNED to live with it. Usually after I get up and get going it stops. On rare occasions I end up humming it for awhile. I wish there WERE some way to make it stop.

  24. I feel your pain. I have had this too for 2 years now. EVERY morning without fail. I hope you find some peace some day. Just wanted to let you know you are not alone.

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  27. I have begun to hate music of any kind because of my earworms. One of the worst ths past 12 months has been Let it Go from the film Frozen. It has woken me up in the mornings many times. I only have to see the word Frozen, or a picture or anything connected with snow, ice, winter etc and the song starts to play on repeat. Sometimes I do enjoy my earworms but this is very rare. When I do find myself enjoying them it's usually because my 'brain'list' (playlist in my brain) is playing something I haven't heard in a long time and have generally enjoyed that music in the past, but these too can swiftly become very annoying.

  28. I have an Earthworm, mine is a cover of 'Hideaway' by Kieza which was covered by a band called Neon Jungle. They are all very talented, young woman and personally I enjoyed listening to their cover today. However, I am now trying to go to sleep, but this damn Earthworm won't let me, Grrrr

  29. does anyone know if with earworms you could do a job in law enforcement

  30. Here the follow up of the paper. New findings confirm and extend the previous but with a twist. http://www.nature.com/srep/2015/150316/srep09162/full/srep09162.html

  31. One direction- everybody wAnna steel my girl, chorus playing on repeat 24/7 in my head, wake up with it playing and go to bed with it playing l, really pissing my off makes me want to smash my head open

  32. its happening since 3 days to me... this song "maybe" be enrique iglesias is stuck in my head... its now getting a lot irritating. i am not even able to study properly at this song keeps distracting me..

  33. same thing here dude... i wanna smash my head too


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