The Gradual Brain-Swap Problem

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The Gradual Brain-Swap Problem

Imagine that instead of swapping one whole brain for another in a single surgical act, we did it slowly, remapping A’s cortical organisation bit by bit until it matched B’s. Perhaps I am to be remapped to my wife (and conversely of course).

At the start, nothing noticeable would happen. A single altered neuron would mean nothing to experience. But as more local circuits were replaced, consciousness would begin quietly rewriting itself from within. Not with a dramatic fracture, but with drift.

Consciousness is not a little spectator lodged in the head, peering at mental content. It is the brain’s ongoing activity of holding a world, selecting, associating, weighting and modelling. The brain does not so much have a self as continually produce one.

As my neural pattern was progressively transformed, my self would not suddenly vanish; rather, the very process that generates consciousness would begin generating a somewhat different subjectivity. Saliences would shift. Emotional tone would tilt. Some memories would lose their grip while alien associations began to feel oddly natural. My inner world would not go dark; it would be revised in place.

From the inside, that would probably feel less like death than like mounting strangeness: a sense that the self I had always taken for granted was becoming less familiar, though without any clean moment at which I could say: that was where I ended. The system would still be producing a first-person world, but an increasingly different one, threaded through with memories that no longer felt quite mine. 

The river would keep flowing, but by degrees it would become another river. I'm not sure this would be any consolation to my wife - whom I had now become.

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Neuroanatomy of the MBTI

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ChatGPT came up with this after much prompting. I know nothing about neuroanatomy, so take this essay as speculative at best.

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Mapping Myers–Briggs onto the Brain: A Neuroanatomical Take on Cognitive Functions and Personality Dynamics

The Myers–Briggs framework posits that our personality is built from two core pairs of cognitive functions - Sensing versus Intuition (S/N) and Thinking versus Feeling (T/F). These are the very processes through which we gather data and make decisions.

But Myers–Briggs isn’t merely a list of traits; it describes a dynamic hierarchy. Depending on one’s type, either a perceiving function (S or N) or a judging function (T or F) sits at the top, with the other assuming a supportive, auxiliary role. (Notably, if your dominant trait is perceiving, your auxiliary is judging - and vice versa.) This dynamic interplay, along with a less-developed tertiary function and a shadow (inferior) function that surfaces under stress, is what Myers–Briggs type dynamics is all about.

Yet, this phenomenological theory can be enriched by looking beneath the surface - to the neural networks that give rise to these cognitive styles. All four functions are mediated by the neocortex, but they differ in their neural “wiring”. 

For instance, Sensing types rely more on primary sensory cortices and lower-level association areas that capture concrete detail. In contrast, Intuitive types engage broader, integrative neocortical networks, enabling abstract pattern recognition and the drive for intellectual cohesion.

Likewise, the Thinking function correlates with robust activity in the dorsolateral prefrontal cortex - our analytical, systematizing hub - while the Feeling function draws more heavily on limbic-influenced regions (such as the ventromedial prefrontal cortex and anterior cingulate), where emotional and social signals merge with higher reasoning.

The next layer of the MB model involves the Extraversion/Introversion (E/I) and Perceiving/Judging (P/J) dichotomies, which determine which of these core functions emerges as dominant in everyday life. 

Extraverts “broadcast” their dominant function, driven by dopaminergic reward circuits in areas like the nucleus accumbens and medial orbitofrontal cortex that energize approach behavior. Introverts, with their higher baseline arousal and stronger inhibitory control from regions like the dorsolateral prefrontal cortex, tend to keep their dominant process internal - thus often expressing their auxiliary function in social settings.

Similarly, the P/J dimension shapes our external engagement. Judging types crave order and closure - a tendency that may reflect tighter, more resolute connectivity in executive circuits that quickly resolve uncertainty. Perceiving types, conversely, show a greater tolerance for ambiguity, their neural architecture perhaps more geared toward continuous information gathering and flexible, open-ended processing.

By situating Myers–Briggs’ phenomenological narrative in the concrete language of brain anatomy, we see a richer picture emerge. Our cognitive functions aren’t rootless abstractions but emergent properties of distinct neural networks.

The S/N and T/F axes provide the basic cognitive “tools,” while the E/I and P/J dimensions determine which tool comes to the fore, and how. In this way, personality is not simply a set of descriptive labels - it is a dynamic interplay between ancient limbic impulses and modern cortical control, a multilevel tapestry underlying human behaviour.