A new study reveals that zoning out during mundane tasks may benefit brain function. Researchers found that mind-wandering ...

sit upright without any lounging or sprawling, look directly at the speaker, maintain an attentive pose, and a placidness of countenance free from any expression, not only of arrogance or displeasure, ...

Even professors of boring subjects can spice it up with some spite. So yah. Our professor decided to do us dirty per retaliation for getting (deserved) low attendance to his lecture the same morning.