Given the task definition and input, reply with output. Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

The “knee-jerk" motion that people involuntarily perform after being struck in the knee in a certain way is an example of a reflex
The “knee-jerk" motion that people involuntarily perform after being struck in the knee in a certain way is an example of what kind of behavior?