Recollections of a former professor, posted by Kai Chang on Overcoming Bias. The teacher purposely told a lie a day:

One of my favorite professors in college was a self-confessed liar.

This was an insidiously brilliant technique to focus our attention - by offering an open invitation for students to challenge his statements, he transmitted lessons that lasted far beyond the immediate subject matter and taught us to constantly checksum new statements and claims with what we already accept as fact. Early in the quarter, the Lie of the Day was usually obvious - immediately triggering a forest of raised hands to challenge the falsehood. Dr. K would smile, draw a line through that section of the board, and utter his trademark phrase “Very good! In fact, the opposite is true. Moving on … “