Study: Slot Machine RTP Warnings Backfire, Mislead Gamblers

Posted on: May 14, 2025, 07:18h. 

Last updated on: May 14, 2025, 09:37h.

Philip Conneller @casinoorgphilc Read More
Expertise: Gaming Business, Regulation, Tribal Gaming.
  • RTP messages make gamblers feel overly optimistic about winning
  • House edge warnings performed better at lowering expectations
  • Misunderstanding RTP could fuel risky gambling behavior

Gambling regulators require that return-to-player (RTP) percentages be prominently displayed on slot machines so that players can make informed choices. But they may be barking up the wrong tree, according to a new study.

RTP, slot machines, gambling psychology, house edge, problem gambling
Your odds of winning at slots may not be as good as you think, especially if you’re reading the RTP wrong, as many gamblers do, according to research. (Image: BetMGM)

Previous research has indicated that most players misunderstand RTP, often leading them to overestimate their perceived chances of winning.

The new study from the University of Nottingham’s School of Psychology in the UK sought to test the impact of an industry-average RTP message and whether it inflated perceived chances when compared to no information at all. Spoiler: it did.

What is RTP?

RTP, usually shown as a percentage, tells players how much money a slot machine pays back to players over time. So, if a slot machine has an RTP of, say, 90%, that means for every $100 bet, it will pay out $90 on average over time. The other $10 is kept by the casino. That’s their profit, aka the “house edge.”

Crucially, this is a long-term average based on millions of spins. It doesn’t mean you’ll get 90% back when you play one individual session. Nor does it mean that 90% of players win – another common misconception.

Slot machines are random. Some people might win big quickly. Others might lose everything even quicker, even on a machine with a high RTP.

What RTP doesn’t explain is volatility (how streaky wins/losses can be), hit frequency, or maximum loss.

Five Times More Optimistic

The study, titled “Never Tell Me the Odds: Typical Return-to-Player Information Increases Gamblers’ Perceived Chances of Winning,” published in Science Direct, tested 6,000 slots players from the UK and the US.  

The players were shown one of four messages before trying a new slot game: a typical RTP line (“This game has an average payout of 90%”), one of two “house edge” warnings (“This game keeps 10% of all money bet” or “This game is programmed to cost you 10% of your stake on each bet”), or no information at all. Then they were asked: How likely do you think you are to win?

The results were striking. Players shown the standard 90% RTP message were more than five times as likely to rate their chances of winning as high, compared to players who saw no message at all.

Both house edge messages performed significantly better than RTP at keeping expectations in check — though no better than showing no info at all.

Interestingly, people who tested higher for problem gambling overestimated their chances only when they saw no information, suggesting they might be especially prone to filling in the blanks with hope.