You need somebody to challenge Groupthink in every team, but you also need a function to challenge it at the corporate level: Group Internal Audit can play that role too.
Groupthink is a mode that a group of people gets into when they desire harmony in decision making without a realistic appraisal of alternatives and where there is a desire to minimize conflict.
Sure, we all want harmony in decision making, that makes our jobs easier, but does it give us the best decision? Most likely not. Let’s face it, how many times have we been in the situation where we know what we’re doing isn’t right, but the effort required is just too great considering your workload or the political cost.