In defining groupthink, it must be explained by its symptoms that describe the effects it causes. Conformity starts with an ideal and a consensus among the people for that ideal. Once that ideal has achieved consensus (all in agreement), people strive to fit that ideal. To go against that ideal would be crossing the line and one would be labeled deviant. This is where a few of the symptoms of groupthink apply. To avoid deviating from the consensus, one practices self-censorship, disregarding issues they disagree with in order to agree with the consensus. One may also come to believe that everything said and agreed within the group is true and that everyone in the group agrees even if they're silent. This symptom is known as unanimity which halts the individual person from becoming a critical thinker, but rather urges the individual to agree with the consensus since everyone else does. As the group grows closer, so do the boundaries of conformity, as disunity among the group becomes the greatest threat.

The rest of the symptoms that suggest groupthink is developing or in the works are very similar to one another. It starts with the group's priority. The group's main priority as it gets closer is the consensus; what they have come to believe and what they all supposedly agree with. This unity among the group members creates a sense of pride. With this united sentiment it is easy to develop the symptom of invulnerability which is the shared illusion that the group is very powerful, therefore inclining the group to take more risks. It is this illusion that fools the group into ignoring and disregarding warning signals that are possibly critical. Morality also serves as another symptom of groupthink as it becomes less questioned among each individual as they soon believe that what the group believes and does is always right. The group begins to justify its actions even if what they've done is extremely questionable. This is the symptom known as rationale. As the group falls deeper into groupthink, other symptoms begin to appear and develop. Stereotypes develop and are shared among the group members. Ideas that the enemy are always wrong and always evil become truth and justify the group's actions to attack them. Added pressure becomes a motivator for an individual to keep quiet if he disagrees with the consensus. He'd rather not look like the odd ball out, and he'd rather not appear to be disloyal to his leader. It becomes important to each group member that disunion not be a threat and that everyone continues to support the leader. These priorities lead the group to the symptom known as mindguards. If a group member finds that one of the group is disagreeing, thus threatening disunion, he may feel inclined to approach that group member and talk some "sense" into him. By the time the group is deep into groupthink it becomes harder for each individual to see and act critically and individually as they have each grown attached to the group. The group, in a sense, becomes one great big biased brain.

Groupthink, as described by its various symptoms, is a psychological disorder that can seriously bias the decision-making process of a cohesive group. The individuals in the group become less inclined to think critically and the main priority of the group is the consensus. This consensus becomes so important to them that they go out of their way to protect it, fearing disunion would occur if they lost consensus. With their priorities changed, the group members become occupied with the group's goals and soon begin to think alike without question. Thus, groupthink is very much like a downward spiral; with the individuals becoming less individual within time while developing the groupthink disorder.