Sleep Signaling

We sleep less well when we sleep together:

Our collective weariness is the subject of several new books, some by professionals who study sleep, others by amateurs who are short of it. David K. Randall’s “Dreamland: Adventures in the Strange Science of Sleep” belongs to the latter category. It’s a good book to pick up during a bout of insomnia. …

Research studies consistently find … that adults “sleep better when given their own bed.” One such study monitored couples over a span of several nights. Half of these nights they spent in one bed and the other half in separate rooms. When the subjects woke, they tended to say that they’d slept better when they’d been together. In fact, on average they’d spent thirty minutes more a night in the deeper stages of sleep when they were apart. (more)

In 2001, the National Sleep Foundation reported that 12% of American couples slept apart with that number rising to 23% in 2005. … Couples experience up to 50% more sleep disturbances when sleeping with their spouse. (more)

Why do we choose to sleep together, and claim that we sleep better that way, when in fact we sleep worse? This seems an obvious example of signaling aided by self-deception. It looks bad to your spouse to want to sleep apart. In the recent movie Hope Springs, sleeping apart is seen as a big sign of an unhealthy relation; most of us have internalized this association. So to be able to send the right sincere signal, we deceive ourselves into thinking we sleep better.

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  • Rasputin

    “Why do we choose to sleep together, and claim that we sleep better that way, when in fact we sleep worse? ”

    Mate guarding? If so, light sleeping might be a feature rather than a bug.

    • Wouldn’t you need to be even more awake to guard a mate sleeping in another bed or room?

      • If you intended to guard the mate, you obviously wouldn’t allow her to sleep in another room.

        The mate-guarding explanation suggests that males are more affected by the presence of another.

      • Mellissa Joris

        I say “yes” and in regards to watching children rather than a mate.  I never understood why all the “civilized” cultures make their children sleep alone.  We all sleep together as a family and have many restless nights but I wouldn’t sleep at all if I couldn’t be where my children had immediate access to me.

      • IMASBA

        It’s kinda hard holding down a job and not cause accidents at it if you don’t sleep well. If you have a full time job explain to us how you do it.

  • Michael Mouse

    The signalling explanation seems appealing.

    Another explanation that has intuitive appeal is that sleeping in the same bed can increase sleep by reducing procrastination and avoidance about going to sleep. One member of a couple who is resisting going to sleep at their chosen time may be nudged (or strongly enforced) to come to bed; another who wakes in the night may be more likely to lie still and try to get back to sleep rather than getting up and reading and thus disturb their partner.  Pair working is at least anecdotally known to increase time on task; pair sleeping might work by a similar mechanism.
    This effect would be very hard to pick up in lab studies, though, where the social pressure of the sleep lab will be different to that available to a solo-sleeping person. In particular, from the accounts, there is considerable white-coat pressure to go to sleep when instructed, stay in the bed and at least appear to try to sleep all night, and get up at the appointed time in the morning.

    This could, of course, be settled empirically and may well have been – particularly in this era of widely-available small-scale sleep monitoring devices (there are plenty of smartphone apps that claim to do this). But it wasn’t obviously addressed in the papers I could easily put my hand on.

    • Sharon Weinberger

      At times like these (where I read of your experimental suggestion in your final paragraph) I wish there was a Kickstarter-like tool for an interested layperson to coalesce support around a simple (or complex) research topic, attract enough interested people to pledge their monetary support, and then attract a researcher of enough skill and time to engage in the desired research.

  • Hmmm. I have suffered from insomnia for decades but slept like a rock when my last SO was curled up beside me with her head on my chest.

  • the_unloginable

    More sex but worse sleep?  Certainly seems like a reasonable tradeoff both rationally and evolutionarily, without invoking signalling.

    • lemmycaution

       Right.  Plus, for a big chunk of history people had 10-12 hours to get in 8 hours of sleep.

    • Nikki

      Does anybody actually do that? Have sex *because* they are already in the same bed anyway?

      • the_unloginable

        On the margin? Yes, absolutely

      • Mellissa Joris

        YES!  His body curves around you and suddenly you forget your guilt about screaming at the kids, that you’re exhausted, that you haven’t seen him all week and sort of think he’s a jerk.  He feels great and your turned on.  After the sex the endorphin remind you that he’s actually so amazing and supportive and aren’t those babies just so cute?  Sleeping together is important.

      • Nikki

        This comment propels your reply to Prof. Hanson from the domain of merely creepy into the outstretched arms of “CPS’ involvement required immediately.”

      • Booyah987

        I tend to agree, and I’m male.

    • More sex but worse sleep?  Certainly seems like a reasonable tradeoff both rationally and evolutionarily, without invoking signalling.

      At first sight, this seems to miss the point: the signaling explanation isn’t to explain the willingness to forgo some sleep but to believe that we aren’t forgoing it.

      But on second thought, it does suggest an alternative explanation: the cognitive dissonance of the belief that we have to endure bad to obtain good, an extensively demonstrated effect obtaining even when no deception of others is involved. (For my theory of cognitive dissonance as cognitive disfluency, see “Uncomfortable ideas and disfluent expression affect us similarly” — )

      This issue of discriminant validity applied to theories invoking signaling highlights the dangers of exploring a field with several pet mechanisms — without considering alternative explanations.


    “Why do we choose to sleep together, and claim that we sleep better that way, when in fact we sleep worse? This seems an obvious example of signaling aided by self-deception.”
    Yup, sleeping alone makes you feel better rested when you wake up, I never had delusions about that, but I understand that it may be hard to tell your partner they’re keeping you awake so you chose to lie about it and since your partner has the same problem he/she knows you’re signalling devotion. That said, it does also depend on other factors. In the study the average sleep disturbance is probably increased because a fraction of people snor/sleep with their mouth open, a fraction of people share a blanket (which is a bad idea) and a fraction of people are literally clingy. So if you leave each other alone during the night, breath through your nose, don’t snor and have separate blankets your sleep disturbance won’t be as extreme as what they found in this study.

  • cd

    I always wake up a few times in the middle of the night. When I’m alone I find this quite unpleasant, but when I’m with my partner it’s very enjoyable to lie half-awake with him until I get back to sleep. I might get more or deeper sleep alone, but it’s just less pleasant. I don’t think we need to invoke signalling; people are just using two different definitions of “better.”

  • Nikki

    The self reports are not necessarily incompatible with the research results. There’s a difference between sleeping alone as part of an experiment and sleeping alone in real life. The latter often involves troubling/stressful circumstances: maybe the partner is in the hospital, or you just had a fight or broke up, or you work the night shift and your partner doesn’t and you’re both fed up with that but your employment options are limited, etc. In brief, the usual “correlation != causation” story.

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  • Philo

    “[O]n average they’d spent thirty minutes more a night in
    the deeper stages of sleep when they were apart.”  The obvious question (already brought up in the comments by cd):  is thirty minutes more in the deeper stages
    of sleep *better*?  If not, then the study does *not* show that sleeping alone produces better sleep.

    In my own experience, sleeping alone has been generally less
    pleasant.  (My wife doesn’t read this
    blog, so in saying this I am *not signaling*.)

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  • comingstorm

    Hmm.  Never mind the methodological problems due to disruptive, uncomfortable sleep studies.  Consider this question: given the choice, would you rather be sleep-deprived or lonely?

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