Leech

• In an article published today in Proceedings of the Royal Society B, we argue the evolution of all these kinds of animal intelligence has been shaped by just five major changes in the computational capacity of brains.
• Each change was a major transitional point in the history of life that changed what types of intelligence could evolve.

The coordination problem

• Some have argued single-celled organisms show adaptive and complex behaviour and forms of learning, but these are limited to life at tiny sizes.
• However, a multi-cellular body need to be coordinated to actively move as a single entity.
• A nervous system solves that coordination problem.

Growing a brain

• With this came a brain, and the capacity to combine information from different senses.
• A brain can be the master coordinator of the whole body, and this let new types of bodies evolve: bodies with specialised limbs and special sensory structures.

A feedback loop

• The third transition was to more complex brains, specifically ones with feedback.
• Read more:
  Bees can learn the difference between European and Australian Indigenous art styles in a single afternoon

  Insects have recurrent brains.

Parallel processing

• Here information flow iterates through recurrent systems.
• This allows massive parallel processing of information.

The brain that modifies itself

• A reflective brain can learn the best information flow for a specific task and modify how it processes information on the fly to complete the task in the fastest and most efficient way.
• The human brain is reflective, and this capability has enabled our imagination, our thought processes and our rich mental lives.

Different brains for different lifestyles

• Each transition changed in fundamental ways what the nervous system could do and opened up new possibilities for cognition.
• Our story describes five fundamentally different types of brain.
• One is not better than another, each is just different.
• Different types of brains suit animals to different lifestyles, and support different types of animal minds.