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Comment by frereubu | Hacker News Reader

The language here is weird. He's talking about doing more than one thing at a time. If you're talking about multi-threading in the context of the brain, the obvious comparison is with neural architecture. The brain does a massive amount of parallel processing and it very much is multi-threaded. But "multi-threading" sounds a bit cooler than "doing more than one thing at a time" I guess.

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Yes, the title is rather poor. From reading the post, it seems what he really means is: "Mental Context Switches are Really Expensive". That's far less exciting, and probably also kind of obvious to most knowledge workers.

I think the title should be "Attention is not multi-threaded", which I believe is pretty well known in psychology and where the expensiveness of context switching stems from.

I wish more places and people understood this!

I am of the opinion that this for instance might be the biggest singular reason nodejs has been successful without people even realizing it. Since “full stack” development is so in demand/popular this really limits the context overhead of switching languages and semantics between front end and back end in such a way that it can keep productivity high.

(Yes nodejs has other strengths too and to be fair weaknesses but I wouldn’t discredit this as A much factor off hand at least)

I have ADD, and I've been using a context switch for years to explain why it's so hard for me to change between two totally different tasks, but I can change pretty rapidly (with no penalty) between multiple similar tasks.

I've likened it has having to pack up one set of tools, before I can unpack the other one.

I find that when doing something less interesting I tend to switch back and forth between two tasks quite a lot while working - each switch acts to regain attention before it starts dropping off again. As long as nothing external forces me to context switch this both keeps me focused and drives my boss nuts.

Yes, and we're talking about conscious thought with context switching; not necessarily subconscious thought. You can drive or bicycle and actively be thinking about that conversation you had yesterday. Both are complex tasks.

The brains of mammals work very differently from the machines we create. We don't understand exactly how, but they are substantially more complex. Just look at how much work goes into writing a machine that can classify photos as cats or dogs; or software that can drive an autonomous vehicle.

Once a certain skill is fully internalized, using it may require no attention at all.

It's similar to growing a coprocessor designed to do this task, load on CPU is reduced and you may also get a small cache to buffer it for a while without losing context even if interrupted.

It has limitations, too complex tasks are hard for brain to make automatically facile.

Or, when you're trying to fall asleep, find yourself simultaneously mentally singing an earworm while thinking about code while trying not to think of some past trauma. It seems an everyday experience to have multiple streams of thought all at the foreground.

> That's far less exciting, and probably also kind of obvious to most knowledge workers.

I think his point was that, obvious or not, many knowledge workers organize their work that way and this will actively cause psychological harm.

I wasn't fond of his technology metaphors either, but I think the point he wanted to make was a valid one.

Though, using the metaphors as a tool of argumentation might also make sense because do use terms like "multitasking" a lot when describing situations where you have to switch around between different activities a lot (and implicitly justifying it because the activity is also seen as simple and basic - because computers do it all the time)

So it might be useful to drill down on those metaphors and show how incorrect they actually are.

(If you want to nitpick on the metaphors, I think he had threads in computers come off too easily: As probably every kernel developer can tell you, OS context switch absolutely do involve a complicated machinery of instructions - and as every application developer knows, having multiple threads can absolutely lead to chaos if you have no strategy how to manage them)

There is a big difference between multitasking and parallel processing. As a former neuroscientist I get rankled when I read gross conflations like this, it doesn't help anyone understand how the brain actually works, nor does it effectively underscore the attentional drawbacks of trying to multitask.

True, but from a big-picture view he might be doing a better job explaining the concepts to laypeople. And in that it might help them improve how they work / live :)

Sure, the layperson knows what multi-threading is.

The lay hacker.

I think a better analogy is the way GPU calculations are done, as the calculations are done in parallel but the process is ultimately sequential: move data from CPU RAM to GPU RAM, calculate in parallel on GPU, move results data back to CPU RAM, operate on the results data on the CPU serially.

Fellow former neuroscientist here! The proliferation of pseudo-neuro explanations and analogies is infuriating. I envy people like theoretical physicists who work in a field where laypeople don't feel like they have an intuitive understanding of their subject area.

Maybe you haven't noticed how "quantum" is being thrown around these days, check https://en.wikipedia.org/wiki/Quantum_healing and https://en.wikipedia.org/wiki/Quantum_mysticism

I for one am a specialist on quantum mechanics since I read Steven Hawking. It's all bonkers, I can tell you that, but because of the uncertainty principle, I'm not really sure. That's OK because there is some parallel world in the multiverse in which it isn't. And please don't ask me to explain, I've read enough to know that by Hoffstadter's Incompleteness theorems I cannot prove it.

I know that dog created the universe with a pair of parentheses and after that it was pretty much backwards and uphill.

ok maybe not: https://xkcd.com/224/

I remember Richard Feynman (a theoretical physicist) explaining how you could deduce things about the human mind by observing behavior and self-reported internal states.

I really wish there were more books for laypeople by neuroscientists. I don't care much for theoretical physics personally, but a lot of people want to understand their own brains.

> lot of people want to understand their own brains.

You are what you think. I have no idea how or why... but I know this is so.

>You are what you think. I have no idea how or why... but I know this is so.

Given the evidence that conscious thought, self-awareness and "free will" are post-hoc effects, emerging after decisions are made by the brain at a subconscious level, it's more likely that that you are what thinks you.

I gather there is some debate in the field as to whether this is a true effect or a consequence of bad measurements. I do find it fascinating and await better evidence before making my mind up either way.

I do, however, appreciate your splendid and witty statement and shall reward you with an upvote :-)

> Given the evidence that conscious thought, self-awareness and "free will" are post-hoc effects, emerging after decisions

But I thought I was a racer from age 6... and now I are one.

Former physicist here! Hearing people talk about vibrations, entanglement, dimensions, quantum and other specific terminology in a more or less woowoo/spiritual context is just as infuriating.

Fiction writer here. If I had a penny for each time one of my readers asked, "So did they go to another dimension?"...

The brain is more like SIMD than multicore processing, but I think a better analogy is a FPGA; it can do heterogenous instructions, but switching from one task to another is a crushingly expensive stop-the-world affair.

Possibly people assume that they are conscious of all the tasks that their brain does?

Can they walk and chew gum?

You are conscious of most things your brain does. Background tasks like walking and chewing gum tend to be very rote and decision light. Try and write while listening to someone speak, fold a paper airplane while navigating a new city, or program while watching a film.

Writing, listening, watching a film and navigating a new place all require attention as they're novel activities. But I could easily make a shit paper aeroplane while navigating, and I've coded through pure muscle memory plenty of times. Almost any activity can be internalised.

> I've coded through pure muscle memory plenty of times

How many lines of code though? :D

Couldn't tell you, wasn't paying attention ;)

I'd call it more similar to a computer system with multiple specialized processors working in parallel and limited buffers between them. Parallel system, really, not multithreaded.

All mostly stuck on a single bus and constantly blocking.

But isn't the brain massively multitasking? It controls and keeps track of an awful lot of stuff. The "can't do multiple things [well] at once" really just applies to conscious efforts.

It is, but that's not what the article is about.

Maybe he meant the conscious mind we experience abstractly and is somehow hosted in / by the brain.

In which case, sure, it makes sense that each thought blocks the main thread and that's why thought-loops are particularly annoying.

In terms of I/O though, I certainly try to optimize the main thread with concurrent patterns when the input queue gets hit with high traffic. Even if I'm recurrently mulling over something for days, hoping for a break-through or insight or whatever, it's not like I'm incapacitated and can't perform / prioritize other thoughtful tasks on the event loop.

The keyword in the previous person's comment is attention. It's attention that is incapable of multi-tasking. It really just bounces from one thing to the other and attention is sort of what drives consciousness and directs it where to go. But the rest of the brain is doing a ton, such as memory encoding to both working and long-term memory. It's also doing things like language, motor, emotional processing, etc. as well as all the things more peripheral to consciousness like senses, time, vitals, etc.

If we look at the brain like a computer that interacts with the world as well as interacted with, I like to imagine that the brain is very complex and running many parallel processes. Like a computer, it has many parts of the interface to the world. Eyes are the screen, ears are the speakers, muscles are the mouse and keyboard, etc. I like to think of attention as the cursor; sort of a single process that directs what the user is interacting with.

I'm positive that is much too simple of an analogy because it still leaves the question: why can't consciousness control multiple attention cursors simultaneously? In many ways, it does in which consciousness can pass things off to automatic processing, like triggering muscle memory and other previously strengthened pathways. But, I think the why there's not multiple attention processes running is still a big question yet to be answered. I think neuroscience still has a lot to be understood before we'll be able to answer it sufficiently.

It would appear that the prefrontal cortex is much less parallel than the rest of the brain.

This is why we often get much better task performance when we allow our gut feelings (which come from subconscious parts of the brain) to inform our reasoning.

Deliberative reasoning in the human brain has a very limited capacity.

See: https://en.wikipedia.org/wiki/Working_memory and https://en.wikipedia.org/wiki/The_Magical_Number_Seven,_Plus...

Threading has a rather specific meaning in cpus, no?

Synapses are parallel, but so are various operations in a single threaded CPU, even just the ALU (carry look ahead addition e.g.). Vice versa, hyperthreading switches context when the single threaded cpu is stalled by memory look-ups.

While its notable how many ideas can converge, or how you remember that name out of the blue that you couldn't figure out minutes or days before is surely interesting. But attention is pretty much directed, so to speak. Just doing a different motion with each hand at the same time requires a certain ammount of orchestration. This requires planning and training.

The brain is a super scalar architecture, sure, but you cant do taxes with one hand, paint a picture with the other, and explain quick sort to your mom over the phone while you get your ... nippeles pinched (the classic Password Swordfish situation). Or more simply speaking, you can't be angry (at the taxes), elated (because of the forms and colors) and aroused (the nipple pinching throws various interrupts, whether arrousel or panic) at the same time while remaining pleasently calm towards your mum. Well, that does not sound like a good study design, but because of the health hazzard. Come on, if you stress a metaphor, I want too.

No metaphor is perfect - my claim is that this is quite a bad one compared to many others that he could have chosen.

we agree that the choice of words is bad, we agree that the metaphor is appealing, and we can probably agree that we don't know how the brain works.

Mixing behavioral ideas and whatever-else-accurately-describes knowledge of cpus (systemic?) is a bad idea, over all. That's not reductive and breaks the deductive argument.

Perhaps a better analogue would be a largely single- (or few-) threaded main processor with a truly astounding number of single-purpose coprocessors? I.e. physics units (motion vector approximation), graphics units (optical processing), management engines (parasympathetic nervous system) etc.

"In the context of the brain" what is the difference between multi-thread and multi-task? Can you give examples?

I can simultaneously walk and listen to a podcast; but when I hear two overlapping voices I can only parse[1] one of them at a time even though I can easily choose which one of the two to listen to[1].

[1] listen to? Parse? Hear? I’m not sure what the right word is in this context.

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