Roulette Gambler Fallacy

The gambler’s fallacy is a psychological phenomenon that’s the false belief that random events will balance each other out. Based on the “law of averages”, it is the mistaken notion that a particular outcome or event is inevitable or certain, simply because it is statistically possible.

1. The gambler's fallacy is the mistaken belief that some result becomes more likely because of what happened before (or less likely because of what happened before). The reality is that for most casino games, the odds don't actually change. Here are some examples.
2. The gambler fallacy or a popular myth. The gambler's fallacy is a term of gambling terminology which the players can meet while playing different games including roulette casino game. It is considered to be one of the popular roulette myths. The other name for designation this term is Monte Carlo fallacy.

My wife’s family keeps having girls. My wife has two sisters and she and her sisters each have two daughters, with no other siblings or children. That’s nine girls in a row!

⊕Note that girl and boy aren’t the only possibilities. The next child could also be intersex, like fashion model Hanne Gaby Odiele.

Roulette Strategy Gambler's Fallacy

So are they due for a boy next? Here are three possible answers.

• Answer 1. Yes, the next baby is more likely to be a boy. Ten girls in a row would be a really unlikely outcome.
• Answer 2. No, the next baby is actually more likely to be a girl. Girls run in the family! Something about this family clearly predispose them to have girls.
• Answer 3. No, the next baby is equally likely to be a boy vs. girl. Each baby’s sex is determined by a purely random event, similar to a coin flip. So it’s equal odds every time. The nine girls so far is just a coincidence.

Which answer is correct?

4.1 Independence

It all hangs on whether the sex of each baby is “independent” of the others. Two events are independent when the outcome of one doesn’t change the probability of the other.

A clear example of independence is sampling with replacement. Suppose we have an urn with (50) black marbles and (50) white ones. You draw a ball at random, then put it back. Then you give the urn a good hard shake and draw at random again. The two draws are independent in this case. Each time you draw, the number of black vs. white marbles is the same, and they’re all randomly mixed up.

Even if you were to draw ten white balls in a row, the eleventh draw would still be a (50)-(50) shot! It would just be a coincidence that you drew ten white balls in a row. Because there’s always an even mix of black and white marbles, and you’re always picking one at random.

But now imagine sampling without replacement. The situation is the same, except now you set aside each ball you draw rather than put it back. Now the draws are dependent. If you draw a black ball on the first draw, the odds of black on the next draw go down. There are only (49) black balls in the urn now, vs. (50) white.

Figure 4.1: Example of an eikosogram.

We can visualize independence with an eikosogram, which is like an Euler diagram but with rectangles instead of circles. The size of each sector reflects its probability. For example, in Figure 4.1 the proposition (A wedge B) has low probability ((1/12)), while (neg A wedge B) has much higher probability ((1/2)).

Figure 4.2: Example of an eikosogram where (A) and (B) are independent.

When propositions are independent, as in Figure 4.2, the eikosogram is divided by just two straight lines. That way the (A) region takes up the same percentage of the (B) region as it does the (neg B) region. So the probability of (A) is the same whether (B) is true or false. In other words, (B)’s truth has no effect on the probability of (A).

4.2 Fairness

Flips of an ordinary coin are also independent. Even if you get ten heads in a row, the eleventh toss is still (50)-(50). If it’s really an ordinary coin, the ten heads in a row was just a coincidence.

Coin flips aren’t just independent, they’re also unbiased: heads and tails are equally likely. A process is biased if some outcomes are more likely than others. For example, a loaded coin that comes up heads (3/4) of the time is biased.

So coin flips are unbiased and independent. We call such processes fair.[ mbox{Fair = Unbiased + Independent}.]Another example of a fair process is drawing from our black/white urn with replacement. There are (50) black and (50) white marbles on every draw, so black and white have equal probability every time.

But drawing without replacement is not a fair process, because the draws are not independent. Removing a black ball makes the chance of black on the next draw go down.

4.3 The Gambler’s Fallacy

Gambling often involves fair processes: fair dice, fair roulette wheels, fair decks of cards, etc. But people sometimes forget that fair processes are independent. If a roulette wheel comes up black nine times in a row, they figure it’s “due” for red. Or if they get a bunch of bad hands in a row at poker, they figure they’re due for a good one soon.

This way of thinking is called the gambler’s fallacy. A fallacy is a mistake in reasoning. The mistake here is failing to fully account for independence. These gamblers know the process in question is fair, in fact that’s a key part of their reasoning. They know it’s unlikely that the roulette wheel will land on black ten times in a row because a fair wheel should land on black and red equally often. But then they overlook the fact that fair also means independent, and independent means the last nine spins tell us nothing about the tenth spin.

The gambler’s fallacy is so seductive that it can be hard to find your way out of it. Here’s one way to think about it that may help. Imagine the gambler’s point of view at two different times: before the ten spins of the wheel, and after. Before, the gambler is contemplaing the likelihood of getting ten black spins in a row:

[ _ , _ ,_ ,_ ,_ ,_ ,_ ,_ ,_ ,_ , ? ]

From that vantage point, the gambler is exactly right to think it’s unlikely these ten spins will all land on black. But now imagine their point of view after observing (to their surprise) the first nine spins all landing black:

[ B , B , B , B , B , B , B , B , B , _ ,? ]

Now how likely is it these ten spins will all land black? Well, just one more spin has to land black now to fulfill this unlikely prophecy. So it’s not such a long shot anymore. In fact it’s a (50)-(50) shot. Although it was very unlikely the first nine spins would turn out this way, now that they have, it’s perfectly possible the tenth will turn out the same.

4.4 Ignorance Is Not a Fallacy

At this point you may have a nagging thought at the back of your mind. If we flipped a coin (100) times and it landed heads every time, wouldn’t we conclude the next toss will probably land heads? How could that be a mistake?!

The answer: it’s not a mistake. It would be a mistake if you knew the coin was fair. But if you don’t know that, then (100) heads in a row could be enough to convince you it’s actually not fair.

The gambler’s fallacy only occurs when you know a process is fair, and then you fail to reason accordingly. If you don’t know whether a process is fair, then you aren’t making a logical error by reasoning according to a different assumption.

So, is the gambler’s fallacy at work if my wife’s family expects a boy next? As it turns out, the process that determines the sex of a child is pretty much fair.22 The question isn’t completely settled though, as far as I could tell from my (not very thorough) research. So the correct answer to our opening question was Answer 3.

Most people don’t know about the relevant research, though. They may (like me) only know a bit from high school biology about how sex is usually determined at conception. But it’s still possible for all they know that some people’s eggs are more likely to select sperm cells with an X chromosome, for example.

So it’s not necessarily a fallacy if my in-laws expect a boy next. It could just be a reasonable conclusion given the information available. A fallacy is an error in reasoning, not a lack of knowledge.

Roulette Gambler Fallacy Definition

4.5 The Hot Hand Fallacy

Sometimes a basketball player hits a lot of baskets in a row and people figure they’re on fire: they’ve got a “hot hand.” But a famous study published in 1985 found that these streaks are just a coincidence. Each shot is still independent of the others. Is the hot hand an example of the gambler’s fallacy?

Most people don’t know about the famous 1985 study. Certainly nobody knew what the result of the study would be before it was conducted. So a lot of believers in the hot hand were in the unfortunate position of just not knowing a player’s shots are independent. So the hot hand isn’t the same as the gambler’s fallacy.

Believers in the hot hand may be guilty of a different fallacy, though. That same study analyzed the reasoning that leads people to think a player’s shots are dependent. Their conclusion: people tend to see patterns in sequences of misses and hits even when they’re random. So there may be a second, different fallacy at work, the “hot hand fallacy.”

Things might actually be even more complicated than that, though. Some recent studies found that the hot hand may actually be real after all! How could that be possible? What did the earlier studies miss?

It’s still being researched, but one possibility is: defense. When a basketball player gets in the zone, the other team ups their defense. The hot player has to take harder shots. So one of the recent studies added a correction to account for increased difficulty. And another looked at baseball instead, where they did find evidence of streaks.

⊕But here’s Selena Gomez and Nobel prize winner Richard Thaler telling a bit of the story in a clip from the 2015 movie The Big Short.

The full story of the hot hand fallacy has yet to be told it seems.

Exercises

1. Suppose you are going to draw a card at random from a standard deck. For each pair of propositions, say whether they are independent or not.

   1. (A): the card is red.
      (B): the card is an ace.

   2. (A): the card is red.
      (B): the card is a diamond.

   3. (A): the card is an ace.
      (B): the card is a spade.

   4. (A): the card is a Queen.
      (B): the card is a face card.

2. After one draw with replacement, drawing a second marble from an urn filled with (50) black and (50) white marbles is a ______ process.

   1. Independent
   2. Fair
   3. Unbiased
   4. All of the above
   5. None of the above

3. After one draw without replacement, drawing a second marble from an urn filled with (50) black and (50) white marbles is a ______ process.

   1. Independent
   2. Fair
   3. Unbiased
   4. All of the above
   5. None of the above

4. For each of the following examples, say whether it is an instance of the gambler’s fallacy.

   1. You’re playing cards with your friends using a standard, randomly shuffled deck of (52) cards. You’re about half-way through the deck and no aces have been drawn yet. You conclude that an ace is due soon, and thus the probability the next card is an ace has gone up.

   2. You’re holding a six-sided die, which you know to be fair. You’re going to roll it (60) times. You figure about (10) of those rolls should be threes. But after (59) rolls, you’ve rolled a three only five times. You figure that the probability of a three on the last roll has gone up: it’s higher than just (1/6).

   3. You know the lottery numbers in Ontario are selected using a fair process. So it’s really unlikely that someone will win two weeks in a row. Your friend won last week, so you conclude their chances of winning this week too are even lower than usual.

   4. You’re visiting a new country where corruption is common, so you aren’t sure whether the lottery there is fair. You see on the news that the King’s cousin won the lottery two weeks in a row. You conclude that their chances of winning next week are higher than normal, because the lottery is rigged in their favour.

5. Suppose (A) and (B) are compatible (not mutually exclusive). Does it follow that they are independent? If your answer is yes, explain why this follows. If your answer is no, give a counterexample (an example where (A) and (B) are neither mutually exclusive nor independent).

6. Suppose (A) is independent of (B), and (B) is independent of (C). Does that mean (A) is independent of (C)? If yes, justify your answer. If no, describe a counterexample (an example where it’s false).

In 1913, gamblers at the Monte Carlo Casino lost millions of francs at the roulette table. The ball would land on black, and the gamblers would bet on red. The ball would land on black again, and the gamblers would continue to bet on red.

The ball landed on black 26 times in a row. The probability of that happening was 1 in 66.6 million. To this day, it’s a shocking moment in gambling history.

The 27th time, can you guess what the probability of the ball landing on black would be?

1 in 2, or 50/50.

This doesn’t seem right, but it is. And the people who would have bet on black, after the ball landing on black 26 times in a row, would still only win double what they bet.

This video is all about the Gambler’s Fallacy, and how we convince ourselves that things will “even out” on the gambling table and in other change occurrences.

What Is The Gambler’s Fallacy?

Put yourself in the gamblers at Monte Carlo’s shoes. The ball lands on black. The ball lands on black again. The ball lands on black for a third, fourth, fifth time.

At some point, you’re going to feel sure that the ball will land on red next. There’s a 50/50 chance that the ball will land on red at any given time or on black at any given time. So after a streak of the ball landing on black, you may start to think that the ball has to land on red next.

This is the gambler’s fallacy. It’s a bias in which we let past events influence our decisions and predictions about what will happen next. But this bias is based on fallacy, or a mistaken belief.

The reality of the situation is that the ball has a 50/50 chance of landing on black every single time you play roulette. Each action is independent of the actions before it. Sure, the chances of the ball landing on black 26 times in a row are way smaller than the chances of the ball landing on black twice or three times in a row, but that doesn’t mean that the ball will land on red based on those chances.

The gambler’s fallacy often leads people astray while they’re in the casino. Think of all of the people who continued to bet on red at Monte Carlo. I’m sure some of those gamblers put a lot of money on red, thinking that somehow their chances at winning big were larger just because the ball kept landing on black.

But this doesn’t just happen at the roulette table. Many people will stay at the slots for hours, believing that although they lost time after time again, their chances of winning will somehow increase.

Examples

But the gambler’s fallacy isn’t just a phenomenon that occurs within the walls of a casino. In the “real world,” this logical fallacy can have some pretty serious effects on the ways people make decisions and conduct business.

Roulette Gambler Fallacy Example

Take loans. Approving or rejecting loans can sometimes feel like a gamble to loan officers. Studies show that loan officers are more likely to reject a loan that is sitting in front of them if they had approved the last loan that came across their desk. Researchers think that 5% of loans are affected by this fallacy.

This can have a huge impact on a person’s ability to buy a house or start a business, but further research shows that this fallacy can have an even more significant impact. Asylum judges are not immune to the gambler’s fallacy. Data shows that they are more likely to approve a person’s application if they had denied the previous application, and vice versa.

Explanations

The gambler’s fallacy goes beyond how we make decisions - some argue that it affects how we make sense of the world. Remember, the gambler’s fallacy is a bias that is influenced by past events. We may link our decision to stay at the slots because of past events. But we may also explain what is happening now based on what happened in the past.

We use the gambler’s fallacy to establish patterns. We may get sick and blame it on the bread that we ate before. If we get sick a second time after eating bread, we are very likely to believe that we have an intolerance or allergy involving gluten. But connecting our stomachache to what we ate before isn’t always based in logic or correct probability. Just like connecting the ball landing on red to the ball landing on black before (or vice versa) isn’t always based in logic. Independent events are just that - independent events.

Be Aware of Gambler’s Fallacy

I’m not saying that people with stomach aches shouldn’t write off certain foods or that you should go to the casino and only bet on one color or number. But I am telling you about the gambler’s fallacy so you can be more aware of if you’re using it in your life.

Logical fallacies affect the way we make decisions, form arguments, and predict what is going to happen in the future. Since these fallacies are based on falsehoods, the results may not be so great. The more you are aware of these logical fallacies, the easier it will be for you to step back, make a proper assessment based on facts, and make better sense of what is going on around you.

Quiz

Let’s test your knowledge on the Gambler’s Fallacy.

Question 1:

A coin has been flipped 12 times. 10 of those flips have resulted in “heads.” What is the likelihood that it’s going to be tails the next time you flip it?

Answer:

Roulette Gambler Fallacy Against

50/50

Question 2:

True or False: The Gambler’s Fallacy is just limited to gamblers.

Answer:

False. Everyone is affected at some point by the Gambler’s Fallacy. It’s a common bias that all humans experience.

Last question:

The Gambler’s Fallacy is a _____ fallacy that we should be aware of when making judgements and decisions.

Answer:

Logical