Split brain research and the anatomy of choice

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Jill Bolte Taylor, a neuroanatomist and award-winning author of My stroke of insight, coined the term anatomy of choice. In her book Whole Brain Living (2021), Jill takes a fresh look at the discarded left and right brain theory and explores how science now shows that the asymmetry of these two hemisphere manifests in our lives.

The split-brain research conducted in the 1970s, particularly the work of Roger Sperry and Michael Gazzaniga, provided ground-breaking insights in brain laterisation. However, the findings were oversimplified and misinterpreted by the public and gave rise to the popular idea that the left hemisphere is primarily responsible for logical thinking and the right hemisphere for emotions.

The misconception that individuals can be strictly categorized as either left-brained or right brained led to the belief that tailoring learning programmes and jobs to match a person’s brain dominance, would result in superior performance. However, this oversimplified view ignores the complexity of brain function and cognitive processes. It further ignores the fact that the brain does not function in isolation – it constantly receives sensory organs, including proprioception and touch, balance, smell, taste, hearing sight. These sensory inputs are crucial for perception, cognition and decision-making.

Furthermore, the brain relies on the muscles for executing all output, including body language, speech, writing, negotiating and physical action. Even seemingly simple tasks, such as walking and eating, involve complex coordination between the brain and musculoskeletal system.

Understanding this intricate interplay between the sensory system, brain and muscles is essential for comprehending human behaviour, learning and performance. This underscores the importance of a holistic approach that considers not only cognitive processes, but also sensory sensations and motor functions. By taking into account the entire system, interventions and strategies can be more effective to support learning, enhance performance, and promote well-being.

“Our brain is a magnificent tool that is the home of our thoughts, emotions, experiences and behaviours. When we understand at a cellular level what is going on in our relationship between our thoughts and our emotions, we no longer have to be bound by our emotional reactivity. Instead, we can become emboldened to live our best lives and our best selves. We have much more power over what is going on inside of our heads than we have ever been taught”.              Jill Bolte Taylor


Debunking the notion that the left hemisphere is primarily responsible for logical thinking and the right hemisphere for emotions is straightforward when neuroanatomy reveals that emotional (limbic) tissue is evenly distributed between the left and right hemispheres of the brain. Each hemisphere has both an emotional brain and a thinking brain, which are distinct.

Every thought we have, emotion we feel or decision we act on depends on brain cells to perform that function. Given that the left emotional brain, the left thinking brain, the right feeling and the right thinking brains originate from separate clusters of brain cells, it’s akin to us having four distinct expert resources to tap into.

It follows that each of these expert resources process experiences, information and knowledge in predictably distinct ways, and this diversity lies at the root of relationships with oneself and others. It also explains why we can experience conflicting thoughts and emotions.

From a purely biological perspective we can plot how information streams in through our senses of touch, smell, taste, hearing and sight en route to the brain. These sensations are moderated by the vestibular system, which position experience within the context of gravity, before flowing through the emotional limbic system. Here, sensations are emotionally processed before they are refined by our thinking cognitive brain. From the flow of information it is clear that we are feeling beings who think, rather than thinking beings who feel.

Scientists currently grasp that neuroanatomically most of the commissural fibers connecting the left and right hemispheres are inhibitory. These fibers extend from a particular set of cells in one hemisphere to the comparable set of cells in the opposite hemisphere. At any given moment, both hemispheres contain active cells, yet the cell groups in opposing hemispheres alternate between dominance and inhibition.  Consequently, one hemisphere has the ability to suppress (inhibit) the function of equivalent cells in the opposite hemisphere, thereby controlling the function of that particular group of cells.

When your heart says one thing and your head says another, it simply is a dispute between the parts.


Rather than relying on profiling instruments that pigeon-hole people into one of four types or pop-science aimed at reinforcing stereotypical differences between the two hemispheres, evidence-based research now provides a more comprehensive understanding of both the anatomical and functional disparities between the left and right hemispheres of our brain. Both cerebral hemispheres play a continuous role in shaping our overall experience, from sensory input to the distinctive processing and motor output of our nervous system. As Jill eloquently puts it, “brain cells dominate and inhibit their counter-part cells as standard practice, so the brain is not ‘all-on’ or ‘all-off’ under any circumstances except in death.”


We have two hemispheres and two emotional limbic systems for a reason – to function effectively in the world. Neuroplasticity has shown that when we repeatedly use one of these groups of expertise (expert), we hardwire the gifts associated with that ‘expert’, but also the limitations and challenges when one expert is hardwired to the detriment of the other available, but less accessed ‘experts’. The consequence is that the other experts’ cells become less robust from decreased use, while the most used expert(s) become our hardwired default behaviour which leaves us with limited choices on both biological and psychological levels.

To function effectively in the world we need agility to shift between experts, which can be compared to the gears of a car. If you get stuck in first gear, pull-away and retorts can be quick, but the engine might burn fuel rapidly and even overheat, similar to burnout (left cognitive hemisphere). Reverse gear is appropriate when you ‘retreat to advance’, but when stuck in reverse, one might also get stuck in the past (left emotional limbic system). The lowest gear is aimed at energy efficiency, cruising without a worry in the world and a feeling of expansiveness – one with all. What a journey! However, when stuck in the right cognitive hemisphere, you might run the risk of not being fully functional in this world. In this metaphor, all the gears in between constitutes the playing field of the right emotional limbic system with the emphasis on PLAY. What a personality! What people skills! What flexibility! What creative innovation! What a tsunami. When the default mode is right emotional limbic system, like a tsunami, it might leave instability and insecurity in its wake.

The nature of the brain’s architecture is one of integration, not segregation.  Groups of cells share expertise. When diverse groups of cells are integrated and constantly in communication, mental, emotional and behavioural agility is attainable. The whole is more than the sum of its parts.


The expertise of the left cognitive hemisphere is our power in the world. Processing is verbal, enabling the ability to connect the present moment with past and possible future moments in a structured and sequential manner, resulting in a linear experience if time and thought. This hemisphere is adept at delineating where we start and end, thereby possessing a distinct understanding of boundaries and individuality. Additionally it is associated with qualities such as strength of character and cultivates expertise in goal-driven behaviour, systematic organisation, efficient time management and discerning judgment. However, the cells of the left cognitive hemisphere might lack consideration of others and adversely impact on personal and professional relationships.

The expertise of the left emotional limbic system facilitates the experience of emotions rooted in past experiences, places and timeframes. Emotions such as guilt and shame arose as responses to past occurrences, while resentment accumulates over time leading to the need to blame and a desire for retribution for past grievances. This expert serves as the custodian of all my pain, instilling a sense of caution and vigilance. It guides us to the brink of our potential growth, yet it also has the capacity to retreat into the comfort of the familiar, even when familiarity is detrimental and distressing.

The expertise of the right cognitive hemisphere is non-verbal, with an all encompassing awareness. It unconsciously seeks patters and similarities connecting us with others, and the expansive consciousness of interconnectedness. It embraces change and the viewpoints of others, often surrendering the need to be right and valuing ‘we’ rather than ‘me’. This expert might get lost in the flow of innovation, time and compassion, while diffusing boundaries and losing the ability to say no, be on time and stay within budget.

The expertise of the right emotional limbic system can be likened to a well-honed truth detector with its ability to read non-verbal communication. This expert lives in the present moment and detects threats to safety of whatever nature based on the current circumstances, rather than dwelling on the past, hence displaying a tendency towards forgiveness and non-attachment to any one plan of action or solution. It is intuitive and fearless, often appearing deceptive due to its rapid spinning of innovative thoughts, ideas and possible interpretations. The unbounded energy of the right emotional limbic system may be overwhelming to some, but inspiring and motivating to others. However, at times, it may run out of energy before completing tasks leaving unfinished projects in its wake.


The French philosopher Jean-Paul Sartre noted that, “Life is the C between B and D,” meaning that the life we live is the sum total of the choices we make, or fail to make, between the “B” of birth and the “D” of death.

Understanding the role of our nervous system and its tendency to hardwire frequently used cells and processes of our thoughts and feelings not only has the potential to relieve us of unnecessary mental and emotional anguish and pain but also has the potential to elevate the bar of our mental and emotional well-being. This understanding can leave us feeling whole, fulfilled and adepts at leveraging the various experts in our brains to navigate challenges and opportunities with integrity and authenticity.






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