Updated: Aug 30
I use the following model as a simple way to describe the relationships between primary brain processes. Given the brain has 80-ish billion neurons, 130-ish trillion synapses, and has evolved over hundreds of millennia, this model is about as reductive as you get. (1) I forced myself to put it on a single slide. By the way, the most important takeaway from this model is that the brain is highly interactive and dynamic. While there are distinct functional centers, in order to realize how a single brain function operates, one must understand how it relates to the whole. (2)
My ability to specify this model has evolved as informed by the thinking of others. Thanks to work by Daniel Kahneman, Iain McGilchrist, Albert Einstein, Jill Bolte Taylor, George Dyson, Charles Darwin, Richard Dawkins, Robert Sapolsky, Douglas Hofstadter, and others. Also, a particular mention goes to Jill Bolte Taylor. She is the only brain scientist I'm aware that actually traveled into their brain as an explorer. Dr. Jill did this as a result of a stroke. Her first-hand account of her journey is extraordinary. Her book is called My Stroke Of Insight.
This model uses a concept known as an “emotion tag.” Think of an emotion tag as additional information added to ”flat” sensory input. The degree of intensity generally guides the mental processing path. That is, a high emotion tag triggers the cognitive path via the right hemisphere. Whereas a low emotion tag triggers the cognitive path via the left hemisphere. The tagging concept is consistent with decision research found in the notes section. (3)
Brain Pathway Examples
To add some dynamism to this model, please consider two contrasting cases. The following cases are extreme examples to demonstrate the brain's different pathways. Remember, the brain is incredibly dynamic, even in these extreme cases, the brain is still fully engaged, just more in certain functions than others. Next, I will describe each case. Immediately following, I will show each case with a highlighted pathway overlay. These pathway examples are simplistic. The actual path exhibits more feedback loops and interaction.
1) The high emotion tag & low language case - Imagine being chased by a lion. You see the lion and you are in a dangerous situation. The next moment, you are running at full speed, probably the fastest you have ever run. Your will not likely recall a decision to run. It just happened. See the model below, this is a shaded version of the earlier model, with the pathways highlighted. Your eyes provide the sensory input. Immediately your sensory memory is activated and an high-intensity fear tag is placed on the sensory input. Immediately it is routed directly to your right hemisphere. It has no language, but it is fast. Immediately a signal is given to your legs to run. Your brain will also signal hormone production to enhance your body's physical reaction. Your brain, via the neurotransmitter tagging process, likely release hormones to enhance your fear reaction physical performance. Hormones like adrenaline and endorphins should be released in a stressed situation.
This is also the brain case targeted by social media. Social media engages people via emotion and often with augmentation via the addiction-forming dopamine neurotransmitter. Social media may elicit a right hemisphere oriented response. A person may act without control from left hemisphere or related executive functions.
The nature of the emotion tag matters as well. Fear, anxiety and other negative emotions have nuanced impacts as compared to happy, fulfilling and other positive emotions. We provide more context in the article The anatomy of choice - learning from a brain explorer.
Our executive control functions are found in our prefrontal cortex and are associated with left hemispheric processing. Our executive control functions do not fully mature until the mid-twenties, on average.
As such, anyone under 25 should be very careful making big decisions.
It has always been a bit of a head scratcher that (U.S.-based) children are able to get driver’s licenses at 16 and are able to commit to potentially massive, life-altering college debt at 17! Have you ever noticed car insurers have higher insurance premiums for those under 25? Car insurers seem to understand the implications of executive control function maturation and neuroanatomy!
2) The low emotion tag & high language case - You are reading about neuroscience. You are studying the different neurotransmitters as they are produced in the brain's limbic system. You have learned the neurotransmitters are like color hues, they are mixed with just a few primary neurotransmitters to create an almost infinite number of combinations. You think about how these mixes affected you in the past and could affect you in the future. You are calm and satisfied by the learning. See the model below, this is a shaded version of the earlier model, with the pathways highlighted. Your eyes provide the sensory input. Your long-term, declarative memory is activated and either no or a very low-intensity emotional tag is placed on the sensory input. It is routed directly to your left hemisphere. This is where the connections are made to the past and the future. This is where cognitive-based analysis is processed. It has significant language but is relatively slow. The signal of your learning could take days or longer to fully process. Sleep also affects your ability to process and remember.
A cognitive bias is a systematic error in thinking that occurs when people are processing and interpreting information in the world around them and affects the decisions and judgments that they make. In the context of the brain model pathway, The "high emotion tag & low language" case is the generator of cognitive biases. There is a rich literature base of our many cognitive biases. Daniel Kahneman and Amos Tversky's classic Judgement Under Uncertainty comes to mind. Also, it is cognitive biases that present challenges to our everyday life. For example, cognitive biases impacting saving and investing, are:
Time Discounting Bias - preferring immediate gratification over long-term financial goals
Procrastination Bias - delay in completing an important task
Confirmation Bias - retaining selective information that confirms existing beliefs
Salience Bias - over-weighting immediate, easy to perceive information at the expense of under-weighting longer-term, harder to perceive information
It is no wonder then why 1) savings must be intentional, and 2) the U.S. has a very low retirement saving rate! Our own brains are naturally NOT wired for long term savings.
The next passage is from Jill Bolte Taylor’s book. At this point, she is experiencing the stroke and aware of the unique nature of her Brain’s Right Hemisphere as her Left Hemisphere is intermittently on and off line as per the stroke originating in her left hemisphere.
“Imagine, if you will, what it would feel like to have each of your natural faculties systematically peeled away from your consciousness. First, imagine you lose your ability to make sense of sound coming in through your ears. You are not deaf, you simply hear all sound as chaos and noise. Second, remove your ability to see the defined forms of any objects in your space. You are not blind, you simply cannot see three-dimensionally, or identify color. You have no ability to track an object in motion or distinguish clear boundaries between objects. In addition, common smells become so amplified that they overwhelm you, making it difficult for you to catch your breath. No longer capable of perceiving temperature, vibration, pain, or proprioception (position of your limbs), your awareness of your physical boundaries shift. The essence of your energy expands as it blends with the energy around you, and you sense that you are as big as the universe. Those little voices inside your head, reminding you of who you are and where you live, become silent. You lose memory connection to your old emotional self and the richness of this moment, right here, right now, captivates your perception. Everything, including the life force you are, radiates pure energy. With childlike curiosity, your heart soars in peace and your mind explores new ways of swimming in a sea of euphoria. Then ask yourself, how motivated would you be to come back to a highly structured routine?”
Dr. Taylor also makes the following observation:
“We are feeling creature who think”
As the model suggests, the emotion-based limbic system receives information via our nervous system (and brain stem). It is our emotions that first react to sensory information. Our cerebral cortex, left or right hemisphere, regulates and processes the limbic based information.
In the Pulitzer Prize-winning book, Goedel, Escher, Bach; the author, Douglas Hofstadter, makes the comment “Apparently the master wants to get across the idea that (Zen) enlightened state is one where the borderlines between self and the rest of the universe are dissolved." Jill Bolte Taylor’s experience seems to validate the notion of enlightenment as a right hemisphere endeavor and as necessary to quiet the left hemisphere. This could represent the paradoxical "dualism" of enlightenment, that is, "learning without learning" or "thinking without thinking."
(1) To provide relative size context for your neurons and synapses. Let’s say you could rent the synapses found in your brain for $1 / synapse. How much would it cost to rent all the synapses found in your brain? It would cost about 1.5x the annual economic output of the entire earth (2017, nominal GDP in US$).
(2) As Hofstadter says in his book Godel, Escher, Bach “the most naive assumption-that there is a fixed group of neurons for each concept (functional center)-is almost certainly false.” Steven Rose in The Conscious Brain and in reference to neurologist Karl Lashley‘s memory experiments: “So far as memory was concerned, the cortex appeared to be equipotential, that is, with all regions of equal possible utility.”
(3) Finucane et al., The Affect Heuristic in Judgments of Risks and Benefits, Journal of Behavioral Decision Making, 13, no. 1 (2000): 1-17.
Finucane describes tagging as:
“The basic tenet in this paper is that images, marked by positive and negative affective feelings, guide judgment and decision making. Specifically, we propose that people use an affect heuristic to make judgments. That is, representations of objects and events in people's minds are tagged to varying degrees with affect.”
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