Psychological forces refer to group members’ personal motives, emotions, attitudes, and values. In the Challenger disaster, lower-level NASA decision makers had initially recommended postponing the launch until the day warmed up. But when higher-ups pressured them to reverse their recommendation, they caved in—perhaps because they were worried about losing their jobs if they didn’t go along.

The decision makers also changed their attitudes about which criteria to use for postponing a shuttle launch. Previously, NASA rules dictated that a launch wouldn’t take place if anyone doubted its safety. But with the Challenger, the rule had changed: the launch would proceed unless someone presented conclusive evidence that it was unsafe. Engineers hesitated to express their inconclusive qualms, and so the launch proceeded.