System 1, in Daniel Kahneman’s picture of the mind, is the part of our brain that is always on. It is the automatic part of our brain that detects simple relationships in the world, makes quick assumptions and associations, and reacts to the world before we are even consciously aware of anything. It is contrasted against System 2, which is more methodical, can hold complex and competing information, and can draw rational conclusions from detailed information through energy intensive thought processes.
According to Kahneman, we only engage System 2 when we really need to. Most of the time, System 1 does just fine and saves us a lot of energy. We don’t need to have to think critically about what we need to do when the stoplight changes from green to yellow to red. Our System 1 can develop an automatic response so that we let off the gas and come to a stop without having to consciously think about every action involved in slowing down at an intersection. However, System 1 has some very serious limitations.
“System 1 detects simple relations (they are all alike, the son is much taller than the father) and excels at integrating information about one thing, but it does not deal with multiple distinct topics at once, nor is it adept at using purely statistical information.”
When relationships start to get complicated, like say the link between human activities and long term climate change, System 1 will let us down. It also fails us when we see someone who looks like they belong to the Hell’s Angels on a father-daughter date at an ice cream shop, when we see someone who looks like an NFL linebacker in a book club, or when we see a little old lady driving a big truck. System 1 makes assumptions about the world based on simple relationships, and is easily surprised. It can’t calculate unique and edge cases, and it can’t hold complicated statistical information about multiple actors and factors that influence the outcome of events.
System 1 is our default, and we need to remember where its strengths and where its weaknesses are. It can help us make quick decisions while driving or catching an apple falling off a counter, but it can’t help us determine whether a defendant in a criminal case is guilty. There are times when our intuitive assumptions and reactions are spot on, but there are a lot of times when they can lead us astray, especially in cases that are not simple relationships and violate our expectations.