On sleeping through seminars

It seems as soon as I enter a lecture theatre I fall asleep..

At the very latest when they turn on the beamer and start talking.

It’s not quite full on sleeping, just dozing off and waking up a few seconds later when my head jolts back up, but it’s frustrating to be completely incapable of listening to someone talk about their research for 40 minutes without falling asleep.

The room wasn’t too warm or too cold, and neither too light nor too dark. The topics were interesting and complicated and the speakers were anything but monotone.

I think I might have a bigger sleep-deficit than I’d imagined..

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Anyone got any good ideas for staying awake?