A special case of choice shift is grouptbink Uanis 1982). Croupthink occurs when pressures to agree are so strong that they stifle critical thinking. For exam ple, Diane Vaughan (1996) showed how groupthink contributed to the tragic 1986 explosion of the space shutte Chalmgr The engineers working on the Challenger all knew before the launch that the shuttle's O-rings probably would suffer some damage. But political pressures to launch the shuttle, coupled with a culture within NASA that rewarded risk taking, helped to create a situation in which the engi neers essentially convinced each other and themselves that the risk of O-ring fail ure was within acceptable limits. As this example illustrates, groupthink often re sults in bad decisions