Never tell me the odds: Typical return-to-player information increases gamblers' perceived chances of winning.

Previous research has shown that gamblers consistently misunderstand return-to-player (RTP) information, and participants shown an RTP of 93% reported that they were more likely to win than those who were shown no information. However, this effect might have been inflated by a higher-than-average RTP percentage. We experimentally test the impact of showing an industry-average RTP message of 90% on gamblers' perceived chances of winning, in two studies across two countries (UK and US). Slot players from Prolific (N = 6062) were shown either an RTP message ("This game has an average percentage payout of 90%"), two different House Edge (HE) messages ("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, and asked to rate their perceived chances of winning at a new slot machine. Across both studies and countries, participants rated their perceived chances of winning as significantly higher with a typical 90% RTP message than with No Information, with large effect sizes (ORs > 5). Both HE messages significantly outperformed RTP, but were no better than No-Information. These effects were moderated by PGSI in the No-Information condition, with participants with higher PGSI responding with higher chances of winning, but not in the other conditions. These results show an undesired side-effect of the consistently ineffective RTP information and confirm the superiority of HE over RTP, although none of the messages were superior to No-Information. Gamblers deserve to be better informed.