“Prior preclinical studies show that acute cannabinoid injections impair cognition.

Here, effects of cannabis smoke on working memory were tested in rats.

Cannabis smoke improved working memory accuracy.

Placebo smoke did not affect working memory accuracy.

Enhancing effects are likely due to THC dose and/or route of administration.”  https://www.sciencedirect.com/science/article/pii/S1074742718302776?via%3Dihub

“Numerous preclinical studies show that acute cannabinoid administration impairs cognitive performance. Almost all of this research has employed cannabinoid injections, however, whereas smoking is the preferred route of cannabis administration in humans. The goal of these experiments was to systematically determine how acute exposure to cannabis smoke affects working memory performance in a rat model.

Exposure to cannabis smoke had no effect on male rats’ performance, but surprisingly, enhanced working memory accuracy in females, which tended to perform less accurately than males under baseline conditions. In addition, cannabis smoke enhanced working memory accuracy in a subgroup of male rats that performed comparably to the worst-performing females. Exposure to placebo smoke had no effect on performance, suggesting that the cannabinoid content of cannabis smoke was critical for its effects on working memory.” https://www.ncbi.nlm.nih.gov/pubmed/30521850