A single stick breaks easily when someone tries to bend it, but tie a bunch of them together they are harder to break. It can also be used as a metaphor for group activities. When a group of skilled individuals combine, they can use their varying skillsets to complete an objective. Parallelly one can also extend their knowledge related to the field by spending time with other individuals with varying experience and expertise in different subjects.
According to studies, people who socialize with other people from different cultures have a much more clear viewpoint of other nations as compared to someone who sticks to their own community.
Lets take an example of a homicide detective, an experienced investigator has more information regarding forensics and technology as compared to a fresher. Dealing with different challenges throughout their career and working with various other sub-divisions, they have an edge over their newer counterparts. On the other hand, if they were to work on their own, it will be hectic and inefficient.
Everything that has its merits will also have some demerits. Working in groups can also negatively affect ones intellect. As mentioned previously, people can also be stagnant in their learning process despite being in a group.
To conclude, various factors affect the intellect of an individual. One such factor is being part of a group that is very diverse in their knowledge base.