It’s by far the most powerful system.
The beliefs and emotions of System 1 are at the origin of the choices made by System 2.
Basically, we react emotionally to a question (System 1).
Subsequently, the reaction of System 1 instructs and creates the response of System 2.
Therefore, the Implicit Reaction Time tests measure the difference in reaction time to the vision of a brand, product, advertising spot, etc..