But isn't trading about having a belief? If everyone believes it's going higher, it goes higher. If everyone believes it's going lower, it goes lower.
Such behavior is usually described as the herd instinct being triggered so that it drives people to make the same decision at about the same time.
Some market participants -- institutional or retail -- spend most of their time researching situations in order to arrive an investment decision.
As it has been said many times over many decades most investment decisions are based on what everyone else is doing, which doesn't require much time or thought.