Complex sentence: In the minimal group experiments it was found that when voluntary study participants were assigned into groups based on something trivial, such as a coin toss, participants exhibited in-group favouritism, giving preferential treatment to in-group members.
Split into simpler sentences: In the minimal group experiments, participants were assigned into groups based on something trivial, such as a coin toss. These participants would then exhibit in-group favouritism, giving preferential treatment to in-group members.