Ask the Slot Expert: The RNG does not directly determine how much is won

Question: Something interesting always pops up with the questions you get. I just wanted to add my opinion to what you answered [last week].

If the screens the questioner showed you were losers, then out of the many possible screen combos that show losers, there are probably many more ways for the RNG to declare a loser, so a particular screen can certainly be what is mapped by more than one random number.

Also likely, if it was a winner, but not a big winner, the same thing could be said about multiple screens, There could be many 5 coin payouts and the same screen could make that payout. Whether you get 3 Jacks or 3 Queens or any other 5 coin payout, the RNG says "pay 5 coins".

I like to look at it this way. I hit the spin button and the RNG tells the machine what, if any, the payout is. Then the machines program (randomly or not) chooses to display a screen (any screen) that shows a result that is consistent with the result determined by the RNG.

Yes, there are a lot of possibilities, but some losing screens seem to appear more often than others. Screens that are "almost winners" show up to encourage players to keep playing, whereas garbage screens make the player feel that the machine is cold and they might stop playing.

As always, reading your column is enjoyable and informative.

Answer: Thanks for the kind words.

Note: the questioner in question is the writer of the letter in last week's column. A couple was playing side-by-side machines and at one point both machines showed the exact same losing-spin screen.

The RNG does not tell the program running the slot machine how much is won on a spin or hand. Let's run through the algorithm on a video slot.

After the player hits the Spin button, the program gets one number from the RNG for each reel. That number tells the program where the reel should stop. The program then evaluates the combination on each payline to see if it is a winning combination and, if it is, pays according to the paytable.

The same RNG function is used on an 85% payback penny machine and a 98% payback $100 machine. The payback is determined by the layout of the symbols on the reels, not by the RNG.

On a video poker machine, the RNG determines the cards that are dealt and the replacement cards that are drawn. The paytable determines how much a hand is worth and the payback of the game.

In the early days of computer-controlled slots, there were machines from one manufacturer that operated similarly to what you described.

In the late 1990s I was able to talk to Randy Adams, the design guru at Anchor Gaming. Unless you're on Medicare, or at least a member of AARP, you won't recognize that name of a bygone slot manufacturer. Anchor Gaming had an innovative machine with a bonus event that consisted of spinning a wheel on the top of the machine. Sound familiar? IGT had to buy the patent for Wheel of Fortune.

Randy used to work at Universal. I asked him how the Universal machines worked. I was hoping for a flowchart or a step-by-step walkthrough the algorithm, but I guess he was so used to talking to journalists, I got the non-technical spiel, even though I told him I had multiple degrees in Computer Science.

Universal's random selection process worked by choosing a specific winning combination or losing spin. If the spin was a loser, the machine would choose a losing combination from a table of losing combinations. Near misses appeared in that table more frequently than they should have given the layout on the reels.

Symbols landed on the payline on winning spins with the probabilities determined by the number of times they appeared on the reels. The symbols on losing spins didn't tell players anything about the real probabilities.

Universal used this "secondary decision" because a losing spin of blank-jackpot-jackpot is not nearly as exciting as jackpot-jackpot-blank.

Regulators determined that this method misleads players. I suspect that they understood how the old electro-mechanical machines worked and required the new-fangled computer-controlled machines to work the same way. The machine must determine where to stop each reel, whether through a clockwork mechanism or an RNG, and the machine must stop the reels at those locations without alteration.

Having two machines show the same screen at the end of a spin is an incredible coincidence. Unless some other things happened that were not mentioned in the letter.

I can think of another way how two machines can end up showing the same screens.

Machines have to have a default screen. Suppose a machine is in attract (demo) mode and someone puts money in or presses a button to put it into game mode. What screen does the machine display?

I'd always assumed that it was the last spin played at that denomination (or denomination and paytable for a multi-game video poker machine). Hence the request that you play off a jackpot.

Then I checked a group of three video poker machines. Each machine showed the same "game over" hand for each denomination and paytable.

Then I looked at two identical slots, side-by-side. Each machine showed a different screen. As I was playing one of them, the other went into attract mode. When that ended, it showed a different screen than it had before. Where did that screen come from?

The request to play off a jackpot is a remnant from the reel-spinning slot and early video poker days when there was no way to change the display without playing the machine. Only one casino has asked me to play off royal flushes in the last decade.

The picture attached to the email showed credits on each machine. Almost nothing can change on a machine while there are credits on it (i.e., someone is playing it).

If the couple had just put money into each machine and taken them out of some mode and into game mode, maybe the machines would have defaulted to the same starting screen. But they said they had both been playing and then stopped after they heard a loud noise.

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