When I was in middle school, we were shown a lengthy presentation on the holocaust.

I secretly sympathized with National Socialism at the time, so I was already rather indifferent to the Jewish plight.

The presentation was trying too hard to be dramatic with the music and transitions, and I burst out laughing in front of the class. My teacher gave me an evil eye and my classmates gasped.

What could have been causing this, scientifically speaking?