Do we need to slow down or power-up our reptilian brain...?

- english gareth lock Mar 06, 2017

This question was posed on the Human Factors Skills in Diving Facebook group following a discussion about the mistake made when reading out the (wrong) winners of the ‘Best Film’ winners in the recent Oscars and thought it worthy of a blog because as I discuss in both the online and classroom-based classes. Ultimately we want to make effective decisions, especially given the limitations of our minds when impacted by stress & fatigue and influenced by our situational awareness but often our brains have different ideas!

To answer the title question we need to look at the concept of reptilian, mammalian (limbic) and human brains, how they impact our decision-making processes and whether they are relevant to diving. Then we will look at the two key areas of research into decision-making: heuristics and biases (HB) and Naturalistic Decision Making (NDM) and their application to diving, and whether we need to, or indeed whether we can, slow it down or not.

The Triune view of the Human Brain

This model of the human brain was developed by Paul McClean in the 1960s and highlights the evolutionary process which has lead to a unique capability. The human brain is recognised as probably one of the most complex items in the universe whose power and working mechanism we have yet to even come close to understanding. The image below identifies the different areas of the brain associated with each concept.

The reptilian brain, the oldest of the three, controls the body's vital functions such as heart rate, breathing, body temperature and balance. Our reptilian brain includes the main structures found in a reptile's brain: the brainstem and the cerebellum. The reptilian brain is reliable but tends to be somewhat rigid and compulsive.

The limbic brain is responsible for emotions, and many decisions and memories have an emotional bias. In fact, research has shown that when the part of the brain responsible for emotion are removed from the brain, it is almost impossible to make a decision because there is no reference to why the decision should be made. The limbic brain is at the core the value-based judgments that we make; judgements that are often made unconsciously and therefore subject to bias and heuristics. The three main parts within the limbic brain are the hippocampus, the amygdala, and the hypothalamus.

The two cerebral hemispheres make up the neocortex. These hemispheres have been responsible for the development of human language, abstract thought, imagination, and consciousness - this imagination and abstract thought provides the ability to problem solve based on mental models or mental simulations commensurate with our experiences.

It should be noted that these three parts of the brain do not operate independently of one another. There numerous interconnections running throughout the brain which influence the different 'parts'. The neural pathways from the limbic system to the cortex, for example, are especially well developed. 


Gareth Lock is the owner of The Human Diver, a niche company focused on educating and developing divers, instructors and related teams to be high-performing. If you'd like to deepen your diving experience, consider taking the online introduction course which will change your attitude towards diving because safety is your perception, visit the website.