I dunno, man. I read through to the study and it's murky AF. It's based on a 25-minute SurveyMonkey multiple-choice questionnaire in which they asked four questions about gaming:

Questions included: favorite games (up to five), number of years playing video games, length of time per week playing video games and number of genres played. The following content variables were extracted from the favorite games listed: Playing Grand Theft Auto (GTA) (Rockstar, 1997/2015) and Call of Duty (COD) (Activision, 2005/2015), Violent, Mature, Moral narrative and Content Rating (mean ESRB and PEGI rating of favorite games; see Table A1, Appendix A).

And then 18 questions about morality, based on the 1992 version of Gibbs Sociomoral Stage Theory:

This measure consisted of 19 questions regarding how the participant usually feels when playing a video game and a score is given to represent the level of engagement (Yes = 2 Maybe = 1 and No = 0). The maximum score on the measure is 38 α = 0.85 (Brockmyer et al., 2009).

That really boils down to 18 questions of "do you have empathy, 2 for yes, 1 for maybe, 0 for no":

Participants’ responses for each question were categorized into a stage of development and moral type, A or B. The eleven questions are split by themes: questions 1 to 4 Contract and Truth; questions 5 and 6 Affiliation (related to helping family and friends); questions, 7 and 8 Life questions, 9 and 10 Property and Law and finally question 11, Legal Justice. There are four stages of development (1–4) with three transitional stages in between each stage. A response is scored by matching the response to the appropriate Criterion Justification (CJ). The CJ are responses grouped by moral concepts, such as; empathic role taking, intrapersonal approval and prosocial intentions and include sample responses listed below to assist matching; for example “you may become friends”

The authors will go as far as saying:

Only the 17 year olds had mature morality into stage three. However, 18 year olds were slightly lower and classed as immature but this is likely to be an artifact of the small sample size.

But don't see a problem that

- Girls don't play Grand Theft Auto (their data)

- Girls have played for half as long as boys (their data)

- Girls play half as much as boys (their data)

Or this whopper of a table:

Yeah - if you play video games, you're at a mean global score of 2.55 on their 3 point scale. If you don't play video games, you're at a mean global scale of 2.44. But if you play video games, you're at 124/135 of their sample and if you don't you're at 9 of 135. Meanwhile, it's easier to assert from their data that boys are more moral than girls than it is to assert that video games make you more moral.

Buuuuut they knew better than to write that paper.