The Khan Academy has earned all kinds of praise for its wonderfully clear educational videos, but Derek Muller, who did his PhD thesis on the (in)effectiveness of science videos, explains his concerns:
Please watch the video, before reading on.
So, the surprise punchline breaks down into these five points:
- Students think they know it.
- They don’t pay utmost attention.
- They don’t recognize that what was presented differs from what they were already thinking.
- They don’t learn a thing.
- They get more confident in the ideas they were thinking before.
The surprise punchline for good students who never went on to teach is this: most people learn little or nothing from school. They don’t get it.
In the physics example, I can see exactly why someone who already knows physics would interpret the video entirely differently from a normal person who doesn’t yet grok elementary mechanics. Force is a well-defined bit of physics jargon that isn’t at all so well-defined for a normal audience. As the ball goes up, its upward velocity — and thus momentum — decreases at a constant rate, passes through zero, and becomes downward velocity — but force, velocity, and momentum aren’t clearly distinct and mathematically defined for normal people. So they follow along and agree that the ball goes up and then comes down. That’s what the stuffy-sounding narrator is saying, right? I already knew that. Jeez.