System One and System Two — the brain's " two independent sytems for organizing knowledge."

Writes Freeman Dyson, explaining Daniel Kahneman's new book "Thinking, Fast and Slow":

System One is amazingly fast, allowing us to recognize faces and understand speech in a fraction of a second. It must have evolved from the ancient little brains that allowed our agile mammalian ancestors to survive in a world of big reptilian predators. Survival in the jungle requires a brain that makes quick decisions based on limited information. Intuition is the name we give to judgments based on the quick action of System One. It makes judgments and takes action without waiting for our conscious awareness to catch up with it. The most remarkable fact about System One is that it has immediate access to a vast store of memories that it uses as a basis for judgment. The memories that are most accessible are those associated with strong emotions, with fear and pain and hatred. The resulting judgments are often wrong, but in the world of the jungle it is safer to be wrong and quick than to be right and slow.

System Two is the slow process of forming judgments based on conscious thinking and critical examination of evidence. It appraises the actions of System One. It gives us a chance to correct mistakes and revise opinions. It probably evolved more recently than System One, after our primate ancestors became arboreal and had the leisure to think things over. An ape in a tree is not so much concerned with predators as with the acquisition and defense of territory. System Two enables a family group to make plans and coordinate activities. After we became human, System Two enabled us to create art and culture.

The question then arises: Why do we not abandon the error-prone System One and let the more reliable System Two rule our lives? Kahneman gives a simple answer to this question: System Two is lazy. To activate System Two requires mental effort. Mental effort is costly in time and also in calories. Precise measurements of blood chemistry show that consumption of glucose increases when System Two is active.

This is a fabulous article with lots of great stuff worth reading, but I just want to lock onto the point about consuming calories. Yes, we're lazy, but we do all manner of ridiculous things to consume calories and they tend to require overcoming laziness. If activating System Two is a substitute for trudging on a Stairmaster or whatever, maybe even lazy people will do it. Can we lose weight by thinking hard? I'll leave it to others to collect and analyze the evidence. That's just my instant, intuitive take on the matter.