Kathryn, I thought you were going to clarify the point that I keep making when people write articles about the lizard brain, and you came close but still missed it a bit!

""Lizard brain" refers to the oldest part of the brain, the brain stem, responsible for primitive survival instincts such as aggression and fear ("flight or fight")"

Actually according to MacLean (1989) and his triune brain theory, they have 25 stereotyped behaviours, all for activities of daily living, none of which involve fight or flight (the closest they get is "Territorial Displays" of turning colors and puffing up in some way.

If we take the "Fight/ Flight" response as an actual biologically programmed dumping-of-chemicals-into-the-body-to-create-a-temporary-supercharge-of-the-body-to-fight-and-flee-more-effectively", then that does not happen till mammals. Lizard can run or attack, but they have no chemically induced advantage over their normal physiological state. Mammals do and it is experienced as the emotions of anger or rage and fear.

It makes sense that mammal can do this, as it is part of their evolutionary physiological structures that allow them to regulate body temperature.

We bond with mammals such as dogs and cats because they have emotional brains. Its very hard to bond with a lizard because they have no emotional capacity, no changes in facial structure to show emotions. They just stare at you, and it's hard to see them as happy, sad, grieving, angry etc, hard to relate and bond with them.

So our lizard brain may involve our addictive and stereotyped behaviours, but its actually the mammalian or or emotional brain or limbic system that causes the fight/ flight (anger/ fear) response as well as the emotions of happy and sad!