Final answer:
Sherif and his colleagues built unity between the two rival groups of boys at the summer camp by introducing an important, shared, superordinate goal and making all of the boys part of a single, named group.
Step-by-step explanation:
Sherif and his colleagues built unity between the two rival groups of boys at the summer camp by introducing an important, shared, superordinate goal. They created a common objective that required cooperation and collaboration from both groups, such as fixing a broken water pipeline. This shared goal allowed the boys to recognize their interdependence and work together towards a common purpose, fostering unity and reducing intergroup hostility.
Additionally, Sherif and his colleagues also employed other strategies like making all of the boys part of a single, named group. They removed the labels and distinctions between the two original groups and instead, formed a new collective identity for the entire camp.
By doing so, the boys no longer saw themselves as separate factions but as members of a larger group, which helped to bridge the divide and promote unity.