Your post mentions relevant concepts like group cohesion, social facilitation and social loafing, concepts central to the field of social psychology. In fact, a study on social facilitation/loafing phenomena by Triplett in 1898 is acknowledged as the first study done in social psychology.
Consistent with the discussion probes, 1. post a description of a situation in which you experienced or observed negative consequences resulting from groupthink or group polarization. 2. Then describe two consequences as a result of groupthink or group polarization in your example.3. Finally, using an article from the current literature, explain how one alternative to groupthink or group polarization could have been used in that situation.