I had an entirely different column in mind for today. But the events of last week were so peculiar, and so revealing of another classic investor foible, that I shifted gears.This will be one of the few Apprenticed Investor columns written in response to current events. I'm doing so because I feel it's necessary to address last week's topsy-turvy market action. More specifically, the investor reaction to it. A brief background: In my day job, I advise institutional investors on the state of the markets. When risk, according to my metrics, has risen unacceptably relative to reward, I become cautious. When the reverse happens, I get more aggressive. This has been my style for some time, and it works for me. Once I explain the process, I'll lay out the mistakes the public makes in reaction to these market calls.