The very primitive part of the brain is referred to as lizard brain or reptilian brain in the non-technical texts.
The lizard’s brain, like many other reptilian brains, does not go further than recognising basic survival needs. Therefore, sometimes the lizard brain functions are presented by 5F model:
- Flight (or sometimes: fear)
In the managerial and business texts, usually the last two functions (fight or flight response) are referred to as lizard brain functions. However, it would be more precise if you consider the following definition:
The lizard brain response is a title for all fast emotional conservative automatic responses of the human brain.