Psychologists demonstrated this in a 2011 study. Participants at the University of Copenhagen were told to perform a computer task. Afterward, some of them were allowed to watch a funny video, while the others were faced with a play button for the video, but had to resist pressing it (akin to a tempting YouTube clip on your computer). When confronted with an additional task afterward, those who had to resist the video performed worse than those who were allowed to watch it.
