Tag Archives: Fallacy

Don’t Fall for the Gambler’s Fallacy: List of Biases in Judgment and Decision-Making, Part 7

A little later in the day than I would have liked, but today’s cognitive bias is the gambler’s fallacy. The bias gets its name from, as you’d expect, gambling. The easiest example to think of is when you’re flipping a coin. If you flip a coin 4 times and each of those 4 times the coin turned up heads, you’d expect the coin to turn up tails on the next (or at least have a higher chance of turning over tails), right? WRONG!

The odds are exactly the same on the 5th turn as the 6th turn as the 66th turn as the 11,024th turn. Why? Because the two instances of flipping the coin are independent events. (Note: we’re ignoring, for the time being, any effects that quantum reality might have on a given event in the past and the future.) So, every time you flip a coin, that’s an independent event — unaffected by earlier events.

Another important example is the reverse fallacy. That is, if we think that heads are “hot” because it’s been flipped a number of time, thinking that there’s a better chance that heads will be flipped is also a fallacy. Again, this is an independent event — unaffected by previous events.

This fallacy is so named because there’s a famous example of the gambler’s fallacy happening at the Monte Carlo Casino where, on roulette, black came up 26 times in a row. A number of gamblers reasoned that red would come up because there had been such an unlikely number of blacks that came up in a row. As the story goes, they lost millions.

Other examples of the gambler’s fallacy:

  • Childbirth: “we’ve had 3 boys, so we’re going to have a girl now…”
  • Lottery: “I’ve lost 3,000 times, so I’m due for a win…”
  • Sports: “Player X is playing really well, they’re bound to start playing bad…”
  • Stock market: “Stock X has had 7 straight down days, so it’s bound to go up on this next trading day…”

Ways for Avoiding the Gambler’s Fallacy

1) Independent Events vs. Dependent Events

The biggest way to avoid the gambler’s fallacy is to understand the difference between an independent event and a dependent event. In the classic example, the odds of a coin landing on heads or tails is — negligibly — 50/50 (I say negligibly because there are those who contend that the “heads side” weighs more and thus gives it a slight advantage). An example of a dependent event would be picking cards from a deck. There are 52 cards in a deck and if you pick one card without replacing it, your odds of picking one of the other 51 cards increases (ever so slightly).

If you liked this post, you might like one of the other posts in this series:

Ignore Sunk Costs: List of Biases in Judgment and Decision-Making, Part 1

It can be really fun to write a series of posts on a particular topic. By my count, I’ve done this at least seven times so far. Today, I’d like to start what I hope will be an oft-read series on biases in judgment and decision-making (to some, cognitive biases). Because of my background in psychology and my interest in decision-making, I thought it would be wise to share with you the things that I’ve learned either through the classes I’ve taken (the classes I’ve taught!) or the research I’ve read. With each bias, my goal is to explain the bias and offer some possible avenues for not falling into the trap of the bias. Today, we start with one of the big ones: the sunk cost fallacy.

Sunk costs are those costs that have already happened and can’t be recovered. For instance, let’s say you buy an apple and bite into it. The money you used to buy that apple can’t be recovered — it’s a sunk cost. Now let’s say the apple doesn’t taste very good (maybe it’s inorganic). You might say, ‘well, I’ve already paid for the apple, so I might as well eat it.’ NO! That’s the sunk cost fallacy! Just because you’ve already bought the apple and paid for it, doesn’t mean you have to eat it. If it tastes bad, by golly, don’t eat it!

That’s a rather basic example of the sunk cost fallacy, so let’s look at one that might seem a bit more applicable. Sunk costs often come into the fray when they’re contrasted with future costs. Let’s say you’ve bought a subscription to a newspaper or a magazine. Because of your subscription, you get a discount when it’s time to renew your subscription. Now, let’s say that in that year of your subscription, you discovered that there was another newspaper/magazine that you preferred (maybe The Economist?). When it comes time to renew your subscription, you look at the two options to either subscribe to The Economist or continuing with your other subscription. You find out that the discounted price for your current newspaper/magazine will be the same price as The Economist. You say to yourself, “well, I’ve already subscribed to this newspaper and spent so much money on it, so I might as well keep subscribing to it.” NO! That’s the sunk cost fallacy. The money you’ve spent on the subscription for the other newspaper/magazine can’t be recovered! You can’t get it back. As a result, it shouldn’t affect the decision you make now about whether to choose it or The Economist

There’s one more quick example that I want to highlight: war. From a paper by a professor at Princeton:

The United States has invested much in attempting to achieve its objectives. In addition to the many millions of dollars that have been spent, many thousands of lives have been lost, and an even greater number of lives have been irreparably damaged. If the United States withdraws from Vietnam without achieving its objectives, then all of these undeniably significant sacrifices would be wasted. [Emphasis added]

Pay particular attention to that last sentence. That is the sunk cost fallacy in action.

Ways for Avoiding the Sunk Cost Fallacy

So, now that we’ve looked at the sunk cost fallacy, how can we avoid it? Well, the first step in avoiding the sunk cost fallacy is recognizing it. Hopefully, the above examples have given you an idea of how this bias can arise. There are a two other ways I want to highlight that you can use to avoid this trap.

1) What am I assuming?

The crux of the sunk cost fallacy is based on an assumption. That is, you’re assuming that because you’ve already spent money on X, that you should keep spending money on X. If you look at what it is that you’re assuming about a situation, you just might find that you’re about to step into the sunk cost trap.

2) Are there alternatives?

Related to the above example is alternatives. You’re not bound to a decision because you’ve made a similar decision in the past. Just because you bought the ticket to go to the movie, if another activity presents itself as more enticing, you’re allowed to choose that one instead. In fact, if when you sit down to watch the movie, it’s bad, you’re allowed to get up and walk out. Don’t fall into the sunk cost trap thinking that you have to stay because you paid for it. There are any number of things you could be doing: going for a walk, calling an old friend, etc.