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Investor Behavioral Biases: Part 1 Thumbnail

Investor Behavioral Biases: Part 1

Over the summer, we will identify and describe numerous behavioral biases. As you learn and explore, we hope you’ll discover: You may be unable to prevent your behavioral biases from staging attacks on your financial resolve. But, forewarned is forearmed. You stand a much better chance of thwarting them once you know they’re there!

Anchoring Bias

What is it? Anchoring bias occurs when you fix on or “anchor” your decisions to a reference point, whether or not it’s a valid one.

When is it helpful? An anchor point can be helpful when it is relevant and contributes to good decision-making. For example, if you’ve set a 10 pm curfew for your son or daughter and it’s now 9:55 pm, your offspring would be wise to panic a bit, and step up the homeward pace.

When is it harmful? In investing, people often anchor on the price they paid when deciding whether to sell or hold a security: “I paid $11/share for this stock and now it’s only worth $9/share. I’ll hold off selling it until I’ve broken even.” This is an example of anchoring bias in disguise. Evidence-based investing informs us, the best time to sell a holding is when it’s no longer serving your ideal total portfolio, as prescribed by your investment plans. What you paid is irrelevant to that decision, so anchoring on that arbitrary point creates a dangerous distraction.

Blind Spot Bias

What is it? Blind spot bias occurs when you can objectively assess others’ behavioral biases, but you cannot recognize your own.

When is it helpful? Blind spot bias helps you avoid over-analyzing your every imperfection, so you can get on with your one life to live. It helps you tell yourself, “I can do this,” even when others may have their doubts.

When is it harmful? It’s hard enough to root out all your deep-seated biases once you’re aware of them, let alone the ones you remain blind to. In “Thinking, Fast and Slow,” Kahneman describes (emphasis ours): “We are often confident even when we are wrong, and an objective observer is more likely to detect our errors than we are.” (Hint: This is where second opinions from an independent advisor can come in especially handy.)

Confirmation Bias

What is it? We humans love to be right and hate to be wrong. This manifests as confirmation bias, which tricks us into being extra sympathetic to information that supports our beliefs and especially suspicious of – or even entirely blind to – conflicting evidence.

When is it helpful? When it’s working in our favor, confirmation bias helps us build on past insights to more readily resolve new, similar challenges. Imagine if you otherwise had to approach each new piece of information with no opinion, mulling over every new idea from scratch. While you’d be a most open-minded person, you’d also be a most indecisive one.

When is it harmful? Once we believe something – such as an investment is a good/bad idea, or a market is about to tank or soar – we want to keep believing it. To remain convinced, we’ll tune out news that contradicts our beliefs and tune into that which favors them. We’ll discount facts that would change our mind, find false affirmation in random coincidences, and justify fallacies and mistaken assumptions that we would otherwise recognize as inappropriate. And we’ll do all this without even knowing it’s happening. Even stock analysts may be influenced by this bias.

Familiarity Bias

What is it? Familiarity bias is another mental shortcut we use to more quickly trust (or more slowly reject) an object that is familiar to us.

When is it helpful? Do you cheer for your home-town team? Speak more openly with friends than strangers? Favor a job applicant who (all else being equal) has been recommended by one of your best employees? Congratulations, you’re making good use of familiarity bias.

When is it harmful? Considerable evidence tells us that a broad, globally diversified approach best enables us to capture expected market returns while managing the risks involved. Yet studies like this one have shown investors often instead overweight their allocations to familiar vs. foreign investments. We instinctively assume familiar holdings are safer or better, even though, clearly, we can’t all be correct at once. We also tend to be more comfortable than we should be bulking up on company stock in our retirement plan.


What is it? You know what fear is, but it may be less obvious how it works. As Zweig describes in “Your Money & Your Brain,” if your brain perceives a threat, it spews chemicals like corticosterone that “flood your body with fear signals before you are consciously aware of being afraid.” Some suggest this isn’t really “fear,” since you don’t have time to think before you act. Call it what you will, this bias can heavily influence your next moves – for better or worse.

When is it helpful? Of course there are times you probably should be afraid, with no time for studious reflection about a life-saving act. If you are reading this today, it strongly suggests you and your ancestors have made good use of these sorts of survival instincts many times over.

When is it harmful? Zweig and others have described how our brain reacts to a plummeting market in the same way it responds to a physical threat like a rattlesnake. While you may be well-served to leap before you look at a snake, doing the same with your investments can bite you. Also, our financial fears are often misplaced. We tend to overcompensate for more memorable risks (like a flash crash), while ignoring more subtle ones that can be just as harmful or much easier to prevent (like inflation, eroding your spending power over time).


What is it? In “Thinking, Fast and Slow,” Daniel Kahneman defines the effects of framing as follows: “Different ways of presenting the same information often evoke different emotions.” For example, he explains how consumers tend to prefer cold cuts labeled “90% fat-free” over those labeled “10% fat.” By narrowly framing the information (fat-free = good, fat = bad; never mind the rest), we fail to consider all the facts as a whole.

When is it helpful? Have you ever faced an enormous project or goal that left you feeling overwhelmed? Framing helps us take on seemingly insurmountable challenges by focusing on one step at a time until, over time, the job is done. In this context, it can be a helpful assistant.

When is it harmful? To achieve your personal financial goals, you’ve got to do more than score isolated victories in the market; you’ve got to “win the war.” As UCLA’s Shlomo Benartzi describes in a Wall Street Journal piece, this demands strategic planning and unified portfolio management, with individual holdings considered within the greater context. Investors who instead succumb to narrow framing often end up falling off-course and incurring unnecessary costs by chasing or fleeing isolated investments.

We will continue our exploration in the near future when we discuss greed, herd mentality, hindsight, loss aversion, mental accounting, and outcome bias.