If you take a look at the interview, Kripke is actually talking about the mortality effects of sleeping, NOT the functional effects. [1] I've seen many studies

If you take a look at the interview, Kripke is actually talking about the mortality effects of sleeping, NOT the functional effects. [1] I've seen many studies showing the detrimental effect of oversleeping (typically defined as >=9 hours) on mortality, obesity and cardiovascular risk. There's not a complete consensus on the whether this effect is true, though, nor on its neurobiological model. For review and meta-analysis, see [2]. On another note, even when we're talking about mortality, I don't think that sleeping 8.5 hours might be worse than 5. That seems to be an off-hand remark during the interview, to me. [1] I don't recall any study looking specifically at task performance after oversleeping. The link to the study in the OP's post (http://www.sfn.org/index.aspx?pagename=news_052008&print=on http://www.sfn.org/index.aspx?pagename=news_052008&print...) is broken. [2] http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2869.2008.00732.x/full http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2869.2008....