The answer is: a group that isn't all that cohesive
Cohesive in sociological context refers to the situation when each group members cooperate with one another in order to help each other survive.
Even though it sounds positive, complete cohesiveness in a study group actually lead to less than ideal performance.
In every study group, there tend to be some individuals who are generally better at studies over the other individuals. This mean that if the group completely cohesive, the better individuals are more likely to be drag down by the others. Because of this, a little bit of individualism tend to be needed for optimal performance.
