  Adding game elements to higher education is an increasingly common practice.
As a result, many recent empirical studies focus on studying the effectiveness
of gamified or game-based educational experiences. The findings of these
studies are very diverse, showing both positive and negative effects, and thus
calling for comparative meta-studies. In this paper we review and analyze
different studies, aiming to summarise and evaluate controlled experiments
conducted within different scientific disciplines. We focus on the clarity of
non-experimental conditions' descriptions and show that in most cases a.
educational methods used in control groups' activities are poorly described, b.
educational materials used in control groups' activities are often unclear, and
c. the starting conditions are unclear. We also noticed that studies in the
fields of computer science and engineering, in general, report results more
clearly than in other fields. Based on the above finding, we conclude with a
few recommendations for the execution of future empirical studies of games in
education for the sake of allowing a more structured comparison.
