Frank Floor Talk: Persistence and slot vultures

May 22, 2024 9:45 AM
Photo: Shutterstock
  • Buddy Frank, CDC Gaming Reports
May 22, 2024 9:45 AM
  • Buddy Frank, CDC Gaming Reports

One of the hot topics in the hallways at the recent IGA show was “persistence abuse”. Operators were lamenting about those players who seek out machines on which the odds of winning improve the more a machine is played since the last jackpot or bonus. Indeed, the list of the Top 25 most popular machines is dominated by those with progressive meters, perceived persistence bonuses or true persistence features.

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Persistence basically means that a machine seems to, or actually does, get better the more it is played. If it actually happens, it is called “true persistence”. If it just seems, or feels like, it gets better; that is perceived persistence. It is only the “true” category that is being abused.

In a detailed and timely set of recent articles, my colleague John Brokopp wrote in March about the psychological appeal of this unique slot mechanic and said, “The concept of ‘perceived persistence,’ as it applies to slot machines, has proven to be a dynamically successful visual created to attract players and increase time-on-device.” In April, he also talked about “true persistence”, noting one source that said, “just because a game employs a persistence-style mechanic does not guarantee it will become a goose that lays golden eggs on the slot floor.”

Not everyone agrees with that from a customer perspective. Advantage player and author Michael Shackleford is no fan of standard slot machines. He says they are “the quickest way to lose your money in the casino”. But in his latest book (“Gambling 102 – 3rd Editon”), he explains “how nine popular slot games can be beaten[i]”. There are actually dozens of machines today in the “true persistence” category he describes that are potential subjects of abuse. He also refers to them as “variable state” or “accumulation” games.

Operators never like it when advantage players, particularly table game players, manage to beat the house and walk away with the house’s money on a “too consistent” basis. However, with true persistence slots, the house never loses. In fact, this type of advantage play can actually boost selected daily profits. So why the concern?


Perhaps Shackleford explains it best when he describes this practice as “vulturing slots”. Again, he writes, “Real vultures seek out dead animals to pick at the leftover meat. They don’t help with the kill, but take advantage of the hard work of other animals who did it … the slot vulture relies on others to do the work putting a machine into a positive state. When a recreational player leaves a machine close to triggering a bonus feature, like a bone with meat on it, the slot vulture swoops in and gets what he can out of the machine, leaving it in a negative state for the next player.”

That is the problem, and it can lead to an eventual loss of revenue over time. Conrad Granito, GM at the Nisqually Red Wind Casino, said recently, “The challenge with ‘vultures’ is that they may hang around a bank of slots they may think is ‘ready’ and the players just enjoying themselves do not feel safe. At that point, the player may call an attendant or security, but most times they shorten their play time and move on. The result is that the casino has lost revenue, and more importantly we may have lost a player.”

He added, “Vulturing slots is an issue we have had to deal with over the years.”


The first mention I can find of a “persistence” style machine came early in the 20th century with the introduction of progressive jackpots. In the photo below of a 1936 Watling “Bird of Paradise” machine, you won’t see any progressive meters. However, you can clearly see a few coins in one of the jackpot hoppers and none in the other one. This game had recently been “hit”. That means, when the winning symbols aligned, the bottom doors to the hoppers opened, spilling all the coins into the tray. The longer this game is played without a jackpot, the more money would accumulate in both hoppers.

Players were quick to like these games for two reasons: 1. In a bank of machines, the game with the most coins in the hoppers would pay the most and therefore stimulate play on that game. 2. Full, or nearly full, hoppers meant the game had been played a lot, and it was considered “overdue” to be hit.

In reality, the machine was just as likely to hit with just a few coins as it was when both hoppers were full. Consider it like flipping a coin. The odds of a head or tail is exactly 50/50 on any given flip. But if you’d seen 20 straight heads occur, instinct (and overall probability math) would favor the next flip being a tail. Nonetheless, each individual flip still has a 50/50 chance to be another head.

If you doubt the wisdom of slot providers producing progressives, watch what happens when the next lottery prize goes above $1 billion. Ticket sales boom. The game’s overall payback percentage increases for the winner, but the odds of any individual hitting their picks remain constant. Same goes for the IGT “Megabucks” slot jackpot.

The next historical persistence bonus was “skill stops”, also from the early 1900s. These were mechanical buttons above each of the three reels. After your first spin, you could press the button and lock any reel, and then play the game again one more time, hoping to add more winning symbols. Today we call that “Hold and Spin”, and it is has been brilliantly updated on games like Lightning Link and Dragon Link. Interestingly, games like these often combine both skill stops (hold and spin) and jackpot hoppers (progressive meters) enabled by modern digital electronics.

The third type of persistence emerged in the 1990s with the invention of “Mystery Progressives” from Aristocrat in Australia and Mikohn in the U.S.  Instead of using the slot machine to trigger the progressive jackpot, they used an independent random number generator (RNG) as the trigger. One had to play the game at a random pre-selected time (or a specific “coin in” amount) to trigger the jackpot. One of the most popular Mystery variants was a “Must-Hit-By” feature. While this type of progressive could hit at any time, it was guaranteed to pay off at or before the posted limit. Versions of this type of progressive are quite common today for both small and large jackpots. You can imagine that as any machine, or one of its meters, gets close to its posted limit, play increases dramatically.


Operators first developed their dislike for vultures when “team players” would take over banks of local-linked progressive machines. While it was not illegal, these groups, backed by someone with a bankroll, would hire a group of players to occupy all the games on the link until one of the machines hit. This worked because when the jackpot was big enough, the team couldn’t lose. The payoff would be mathematically bigger than the amount of money required to hit it. However, this only worked when other recreational players had built up the progressive amount to get the game into this positive state. Because the teams monopolized all the games, average players have no chance to win the bigger jackpot, even though they were the ones who built it. This was a true vulturing abuse situation.

Again, team play was not illegal, and there was no financial loss to the casino. But many loyal customers felt cheated. Linked progressive IGT video poker machines and the early keno “Pot O’ Gold” machines from U.S. Games were frequent targets of these “teams”.

Counter measures included casino rules that at least some seats had to be reserved for “regular” players. Attempts were also made to ban “known” team players. Nothing really worked, and the result has been that, despite their popularity, there are far fewer large banks of locally-linked progressives today. They’ve been replaced by “WAPs” and standalone meters which have less potential for abuse.

There have been few cures for the “Must-Hit-By” vultures. The worst of them use “staring contests”, body odor or obnoxious behavior to force legitimate players off their games when the meters climb. They, too, can be banned; but it is difficult to identify them because, as mentioned above, many guests simply leave rather than complain.

Likewise, with the newer true-persistence games, it is difficult to combat the problem. On a game like Buffalo Link, once the “Buffalo Collected” meter climbs, the game becomes positive. Shackleford puts that number at 1,350. It is guaranteed to hit at 1,800 Buffalos. Players love these games, but seeing advantage players constantly winning is frustrating to both operators and other players.

The chart above from a December 2023 4Q-Report by Eilers & Krejcik shows that games with true persistence perform almost 20% better than house average (a 1.19 index), and almost every game with some sort of persistence performs above house average.

There are a few true persistence games that are seldom abused. These games have very short-term bonus accumulations. The best in this category is the IGT Ultimate X Poker game developed by Hall of Famer Ernie Moody’s team.  The multiplier bonuses are never more than three “plays” away on this game. That is something that few players will abandon or will be bullied off by an aggressive vulture.

As a side note, there are different kinds of slot vultures. If you’re a frequent player and happen to spot an unoccupied game in a positive condition, good for you! If you’re one of those who try to intimidate another player off his/her machine, or never play games unless they are in a positive condition, “may a curse be on your house”.

Maybe some of the abuse will soon disappear by itself. Another chart in the same December report showed that of the Top 10 games each month in 2023, true persistence games went from a high of 20% in February 2023, to zero by December. That slack was filled by “perceived persistence” games and those games with a “combo” of features (80% in December).

As mentioned earlier, perceived persistence is where it seems like a game is getting better the more it is played, yet the odds don’t really change. Leading examples of this are Light & Wonder’s popular Dancing Drums and variants of Aristocrat’s iconic Buffalo[ii].

Let’s hope that those moves continue and will support a “persistent” attitude among customers that slots are fair for all players.

[i] – The “Gambling 102” List: Cashman Bingo; Rich Little Piggies; Scarab; Golden Jungle Grand; Hexbreake3r; Magic of the Nile; Ocean Magic; Golden Egypt; Regal Riches/Prosperity Pearl; Star Goddess; Buffalo Ascension; and Buffalo Link.


[ii] – It is hard for me to mention Aristocrat’s “Buffalo” without pointing out that this wonderful game features a Bison graphic instead of a Buffalo. The latter animal was never native to North America (despite the song about them roaming our home). And they also feature an eagle graphic but give it the sound of a Red-Tailed Hawk. Maybe it’s just because Australians really don’t know much about the U.S. High Plains or, more likely, they couldn’t see using the wimpy call of an actual bald eagle.  Check it out in this audio/video clip:


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