In his sentimental journey, Louis Rukeyser effectively makes the statement, If advisors are bearish, the market is more likely to go upthan go down. Notice that this statement has the form "If P, then Q." Most people experience great difficulty assessing the validity of statements that have this form, which is why they accept false statements as true. The root cause is that people use a heuristic that leads them to search for confirming evidence (where P and Q hold) instead of the logically correct search for disconfirming evidence (where P and not- Q hold).