Tendency for group members to agree with each other and withhold contrarian views.
When we work in groups of competent people, we tend to agree with their opinions and judgement, even though we might otherwise question them. There are many possible causes of groupthink including peer pressure, fear of looking foolish, or simply respect for peers, but groupthink happens in all manner of groups and in groups of all competence levels. The most notable example of groupthink was the disastrous “Bay of Pigs” operation during the Kennedy administration.
To combat groupthink, consider encouraging contrarian arguments where group members actively try to poke holes in a decision or idea. Another technique is called the “13th man,” where you assign one person to be the designated contrarian: It is their job to figure out how a plan, idea, or project can go wrong.