In response to both parents of this comment, my first reaction would be that &quot;of course&quot; it&#x27;s personal: maybe your bed at home is not that great, or a neighbouring mine makes sounds that don&#x27;t register consciously anymore but still keep you up. But then again, in my experience it is a personal thing beyond a person&#x27;s environment. I know people of both kinds and the location does not seem to matter.<p>It&#x27;s often the case in non-exact science studies that the results are difficult to reproduce. Besides the obvious &quot;they&#x27;re not called exact&quot;, it&#x27;s interesting. What is this caused by? Would, in this example, some people lack the &#x27;feature&#x27; of sleeping with half a brain?