Loss-chasing is the tendency to continue or intensify gambling after losing. People who gamble may chase losses within a single session or between sessions. The researchers examined three behaviours of within-session loss-chasing. The researchers used data from the online commercial game Mystery Arena. Data from 2014 to March 2020 on 2713 people were randomly selected by the game operator and provided to the researchers. People were divided into low- and high-involvement groups. The researchers found that both groups were less likely to stop a session after winning. People were more likely to change their stake after losing. However, they increased their stake after winning when they made a change in stake. Therefore, people showed win-chasing instead of loss-chasing in these two behavioural aspects. After losing, both groups gambled more quickly. This showed loss-chasing. But, gambling outcomes had a smaller impact on the speed of gambling for people in the high-involvement group.