One brain, two systems

The brain can be viewed metaphorically as a dual processor. Scientists refer to the processing of immediate emotions, thoughts, and decisions as System 1, or the Automatic Brain. System 2, or the Reflective Brain, is what many of us call "me" and "feels" like a deliberate decision-making process. System 1 largely occurs unconsciously and effortlessly, while System 2 requires intervention and effort.

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Recommended reads related to this topic:

Thinking, Fast and Slow (2011) by Princeton University psychologist Daniel Kahneman