- System 1 comprises the oldest parts of the brain. It operates automatically and involuntarily. This system is always functioning and is responsible for most of the day-to-day activities. It is also responsible for our reactions to danger, novelty, and intuition.
- System 2 allocates attention and completes tasks that require effort. System 2 is a newly evolved part of the brain, and only humans have a highly developed prefrontal cortex.