Slot Machines

Introduction

In my experience slot machines are the most misunderstood form of gambling in the casinos. Not only do most players misunderstand how they work so do the writers of most books on slots machines. Consider yourself lucky to have stumbled upon this page for you are about to learn the secrets behind the reels.

How They Work

Before I explain how modern slot machines work let me explain how they don't work. Many books on slot machines incorrectly say that each reel is equally likely to stop on each position, or stop. They reason that if a slot machine has 20 stops on each reel and one jackpot symbol on each reel, then the probability of hitting the jackpot is 1 in 20 ³ = 1/8000. This was true of the early days of slot machines before they become electronic. Today this is patently untrue.

Modern electromechanical slot machines are governed by random numbers and microchips. Based on evidence from a variety of sources including program specifications for specific slot machines I offer the following explanation of the steps that a three reel slot machines goes through on a typical play.

1. Player initiates a new play by inserting a coin, pulling the handle, or hitting the 'spin' button.
   
   
2. The machine selects three random numbers. These are chosen from a random number generator that is constantly drawing random numbers at a rate of thousands per second. The numbers chosen at the moment the play is initiated are the ones used to determine the final outcome. It is my understanding that the random numbers range from 1 to 2 ³¹ = 2,147,483,648. The random numbers are drawn in a cycle, to insure that each number is chosen once per cycle, but to the player this would not matter since thousands of random numbers are drawn between plays.
   
   
3. The three random numbers chosen will be divided by a fixed number. This fixed number is often 32 but for IGT slot machines with large progressive jackpots it can be 64, 128, 256, or 512. After dividing the remainders will be retained. If the divisor were 128 the machine would have three remainders that would range from 0 to 127.
   
   
4. It is common terminology to think of the remainders as stops on "virtual reels." If the divisor were 128 then the virtual reels would each have 128 stops with each stop being equally likely. Each stop on the virtual reel will be mapped to a stop on an actual reel. Obviously there are more stops on a virtual reel than a typical 22 stop actual reel. Many different stops on the virtual reel can be mapped to one stop on an actual reel. In general there will be a lot more virtual stops mapped to non-paying blank stops than to jackpot symbols. It is also true in general that a disproportionate number of virtual stops will be mapped to the blanks directly above and below a jackpot symbol. In an another effort to build suspense, the first reels to stop will be more likely to stop on paying symbols than the latter stops.
   
   
5. With the final outcome predetermined the reels will actually stop where the virtual reels dictate they stop.
   
   
6. Notches in the reels are used to verify the outcome and payment is made if due.

Myths

Below are some of the biggest myths about slot machines.

• Slot machines stop on any possible set of stops with equal probability
  As explained above this is not true of modern slot machines. Some stops are much more likely than others.
  
  
• Slot machines are programmed to go through a cycle of payoffs. Although the cycle can span thousands of spins once it reaches the end the outcomes will repeat themselves in exactly the same order as the last cycle.
  This is not true at all. Every trial is random and independent of all past trials.
  
  
• Slot machines are programmed to pay off a particular percentage of money bet. Thus after a jackpot is hit the machine will tighten up to get back in balance, and when a jackpot has not been hit for a long time it is overdue and more likely to hit.
  The only part of this that is true is that they are designed to pay off a particular percentage. However the laws of probability dictate that the longer the machine is played the closer it will come to its target payoff, even with every trial being completely random. A jackpot is equally as likely to be hit right after the last one and if it has been fifty million spins since the last one.
  
  
• The casinos place the loosest slot machines close to the front doors and at the edge of aisles.
  This may have been true at one time but no longer is. Now the casinos like to mix their loosest slot machines somewhat randomly about the casino. It is said that loose machines are likely to be in highly visible areas as opposed to being tucked away in corners. The philosophy behind slot machine placement is that the casino wants as many other slot players to notice a big win as possible, giving them more hope for themselves. Slot machines close in places where people are killing time like buffet lines and the airport are usually tight.
  
  
• Hot/cold coins are more likely to yield good returns.
  The temperature of the coin does not matter. This just a superstition.
  
  
• A recently vacated machine is likely to hit within several spins.
  It is said that a lot of old ladies lurk about the slot machines waiting for someone to leave and then they will grab that machine and play it several times, often with great success. While I do not deny that little old ladies are doing this they do not have any better chances of winning than the player who just left. Selective memory and/or a small sample size of observations of this happening are how I account for this misperception.
  

Other Tips

Here are some other miscellaneous tips to help you cut down the house edge.

• Most machines reward you for playing the maximum coins. For example the jackpot may pay 2000 coins with 2 coins played, but 4000 with 3 coins played. In most cases it is advisible to play the maximum coins.
  
  
• Never leave or play a machine that owes you money. Sometimes a machine will run out of money before it is finished paying you off. If you get up someone else can sit at your machine and claim they hit your jackpot. If you put another coin you may lose the evidence so don't touch anything until you are paid off.
  
  
• The looseness of a machine will have a lot to do with its location. Read my remarks above about slot machine placement.
  
  
• Look for who is advertising loose slots and quoting specific payback percentages. These casinos are eager for your business and are willing to reward you with a looser machine for coming in.
  
  
• Even in the same aisle two identical looking machines can be set to different average returns. If your machine is tight it would not be a bad idea to switch to another one.