For me, the key take away point can be summed up in this quote from Prof. Goetzmann: "Once people buy in, they start to discount evidence that challenges them..." I relate this not only to investing decisions in the market, but also to making organizational decisions--investments in capital projects, new strategies, the next corporate buzz. We've all seen or been apart of the exuberant irrationality that leads organizations into malinvestments.
Let's consider the complementary action--saying "no." Against the tendency toward the irrational "yes, Yes, YES!", learning to say "no" is a very important skill to master. It's probably one of the hardest skills to master when people request something from us that makes us feel important and liked.
I think, however, we always need to be aware that many of our initial reactions are often driven by biases. Reactively saying "no," once we've learned to say it and it becomes easy to do, can emerge from the same biases that urge us unreservedly to say "yes." Both incur their costs: missed opportunity, waste, and rework.
The skill more important to learn than saying "no" is acquiring the skill to consider disconfirming evidence, especially when that evidence challenges our dearest assumptions about what is going to make us rich. Let's not be so quick to say "yes" or smug when we say "no." Rather, let's learn the practice of asking,
- "what information might disabuse me of my favorite assumptions?"
- "what biases are preventing me from seeing clearly?"
Failing to learn these, we all too often find ourselves concocting a witches' brew.