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You Actually Share Your Brain With a Silent Stranger

50 videos recommended on HN
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7 HN users recommended this explainer7 months2016–2025 score 7.5
Years with an HN recommendation, 2007–2026

HN returns to it constantly in consciousness and decision-making threads as a clear, entertaining explanation of split-brain.

CGP Grey explains split-brain patients, where severing the corpus callosum lets the two hemispheres act independently. He uses this to explore the idea of two minds in one head.

“I recommend watching this video by GPGrey, one of the best educational channels on YouTube” (HN, 2017)

1 strong recommendations · 6 recommendations · 5 citations · Explainers

12 Hacker News comments

From the HN archive; up to 20 kept per video, favoring different commenters. Recommendations first.

@BoppreH Nov 2016 Recommends
on HN thread My Subconscious Is a Better Developer Than I Am
For mind bending check the great explanation from CGP Grey, "You are two"[1], which argues the two brain hemispheres can operate independently. [1]: [this video]
Explains how brain hemispheres can operate independently.
@glenneroo Apr 2018 Recommends
on HN thread The limits of information (2014)
Kurzgesagt[0] and CGP Grey[1] did a fun little 2-part intro into "split mindedness" i.e. the idea that we may have multiple consciousnesses(?) contending for control. [0] [link] [1] [this video]
Fun intro to multiple minds contending for control.
@surround Aug 2020 Recommends
on HN thread A man who can read letters but not numbers exposes roots of consciousness
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This reminds me of two mind-boggling discoveries I’ve had about the human mind. The first is that the two halves of your brain act somewhat independently. And in rare cases, people’s left and right halves are “split” apart, and they act entirely independently - e.g. their left and their right hands will act separately, or even argue with each other. CGP Grey made a great video about this: [this video] The other is that most people have a “voice” inside their head - e.g. when they read, they hear their own voice inside their head reading; their thoughts are like sentences they “hear;” they could look in the mirror have a conversation with themselves. Some ~10% of people do not have this internal monologue. [link] [link]
Explains split hemispheres acting independently.
@alexpotato May 2025 Recommends
on HN thread The language brain matters more for programming than the math brain? (2020)
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This reminds me of the following quote: "Coding largely involves the 'logical part' of your brain. It tends to not include the 'language part' of your brain. This is one reason why comments you add to code are so useful: they force you to engage both parts of your brain and therefore get better results. This is also why when you go to explain a problem to a colleague, you often have a flash of brilliance and solve the problem: you are reframing the problem using a different part of your brain and the different part of your brain helps solve the problem." I'm sure some readers here will say this is preposterous and there is no such thing as having "two parts of your brain". To them I suggest watching: 1. "You are are two" (about people with their corpus callosum being severed) [this video] 2. "Conscious Ants and Human Hives" by Peter Watts [link]
Shows severed corpus callosum effects supporting two-parts-of-brain idea.

Citations, criticism and jokes

@midjji May 2021 Cites it
on HN thread Making the hard problem of consciousness easier
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Is it hard though? Or is the hard part ethics i.e. personhood, and because the terms are conflated that makes consciousness hard, since it means you cannot accept what consciousness is without needing to also define ethics. Drop the idea that consciousness is sufficient or required for personhood in favor for something more behaviourally consistent like cuteness or power, and things become clearer. There is a part of you which simulates social interaction by learning models of various other agents it has inferred the existence of. As can be expected from something which is looking for agents based on indirect clues, we know this part does struggle with accidentally assigning agency to things which clearly lack consciousness i.e that damned sharp rock you stepped on twice. This part of you is capable of simulating a finite number of simultaneous such agents at a time, meaning it will focus on, as a whole, being able to predict the actions of the agents most often observed. It is also why we would expect it to replace groups of people you only interact with as a group as a "them". It is also very common that the most significant agent to simulate would be you. Hence one of the models being simulated is you. This is what generates the perception of consciousness, why it is you yet separate. It predicts the cognitive bias of the mind body duality, yet maintains the perception of consciousness. A part of you is constantly trying to explain your own actions, but critically, while w
Cited in a discussion of consciousness.
@throwaway3093 Jun 2023 Cites it
on HN thread If I Know what's good for me, why am I sabotaging myself?
Also, neurologically you are not one person. You are two: [this video] It's not hard to imagine the nearly constant competition that erupts between neural sub-networks in your brain -- their collective output signals vying to be the dominant signal. Just stand in front of a bowl of ice cream and try to predict whether you will or won't actually eat it. (Impulse control, etc) Sensory awareness is helpful towards guiding these competitions and impulses into a direction (and a longer term habit) that is more aligned with your longer-term values. Also helpful: engineering your environment. [link]
Supports the claim that we are not one person neurologically.
@patmorgan23 Jun 2023 Cites it
on HN thread Decades-long bet on consciousness ends – it’s philosopher 1, neuroscientist 0
You're probably right. We have a couple examples of this happening. There's the interesting quarks that people with split brain hemispheres experience. [this video] And dissociative identity disorder where there arguably multiple consciousnesses inhabiting the same brain. It is probably an evolutionary advantage that humans have a ( mostly) uniform singular consciousness.
Example of split-brain experiences.

Video list and Hacker News comment labels from HackerTube (prompted by @karpathy), released under ODC-By 1.0, built on the open-index/hacker-news archive. Hacker News data is provided by Y Combinator; comments remain the work of their authors. Video titles, channel names and thumbnails belong to their creators and are shown via YouTube. HackerTube Watch is an unofficial edition. Data export of 2026-10-31.

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