The conclusion of the "study" (from 2016) is that more research is necessary. Study sample size was 60. 40 known chronic users and 20 random sober blokes given sugar pills. "Creativity" measured was "ability to brainstorm" and "ability to recognize mistakes". So essentially the person who ran the study is a boring Poindexter type giving boring prompts that elicit less participation from the stoners who definitely won't care about "making mistakes" when participating in his stupid study for a little weed money.