“Losses disguised as wins” in electronic gambling machines contribute to win overestimation in a large online sample

•Losses disguised as wins (LDWs) are a type of gambling loss that closely resembles a genuine win.•This online study randomly assigned 940 people to view one of two slot machine gambling videos.•One video displayed LDWs and genuine wins, the other only displayed only genuine wins.•On average, participants who viewed LDWs overestimated the number of genuine wins that occurred.•This tendency toward overestimation was observed among both low and high-risk gamblers.