"Simply having this 12-inch Christmas tree in the room with them made them feel less included in the university as a whole..."

"... which to me is a pretty powerful effect from one 12-inch Christmas tree in one psychology lab."

When people who did not celebrate Christmas or who did not identify as Christian filled out surveys about their moods while in the same room as a small Christmas tree, they reported less self-assurance and fewer positive feelings than if they hadn't been reminded of the holiday, according to a new study.

The university students didn't know the study was about Christmas, said study researcher Michael Schmitt, a social psychologist at Simon Fraser University in British Columbia, Canada. Nonetheless, he said, the presence of the tree caused non-celebrators and non-Christians to feel subtly excluded.