6 ms·

"... Our analogies often look to artificial neural networks: for neural networks compute, and they are made of up neuron-like things; and so, therefore, should

"... Our analogies often look to artificial neural networks: for neural networks compute, and they are made of up neuron-like things; and so, therefore, should brains compute. But if we think the brain is a computer, ..." OK, enough of this. Neurons are not computers. There is nothing what can be compared to actual neurons. "Artificial" neurons are just reduced models of the real ones, so that only the "compute" parts are used to calculate input vectors. It's only a fraction of what the real neurons actually do. While I appreciate the article trying to actually understand what's really going on in neural networks, let's not make unnecessary dumbed-down assumptions. At least the subtitle of the article is actually correct. The main title is sensationalist "...17 billion computers!!".

carlsborg 8y ago
All models are wrong, some are useful.
- feanaro 8y ago
  Not all models are wrong, since some may be modelling exactly the aspects of importance and not modelling exactly those which are incidental and of no consequence.
  - joesb 8y ago
    Then they are still wrong. It's just that they are wrong in the part that you don't care about.
    - feanaro 8y ago
      Is it wrong, or is it simply an instance of the fact that a model is not the thing it models? The use of the word wrong sounds wrong to me here. The wrongness should be about whether the model accurately, or just approximately, or not at all, shares with the modelled object that part of the behaviour we are interested in.
  - danmaz74 8y ago
    The point is that no model of a complex real world phenomenon is ever perfect, so, you shouldn't try to create a perfect model. But not being perfect doesn't mean that a model can't be useful; among all the possible "wrong" models, you need to identify the one(s) which is useful, ie, which models well the aspects of importance to you.
    - feanaro 8y ago
      I realize all that. I'm questioning the wisdom of the standard manoeuvre of preemptively calling all models imperfect or wrong, though.
      - danmaz74 8y ago
        Not everybody realises all that, so I suppose the OP cited that quote to reinforce the point that ANN are a very useful, but very imperfect model of the brain. I cite it often enough, but usually it's in person, where I can see the reaction of the person I'm talking with, and explain if necessary.
  - Rainymood 8y ago
    All models are wrong. The map is not the territory. We are arguing semantics now. The point you're trying to argue is that a model is "right" in the sense that it models whatever we wanted it to model. We argue that a model is "right" if it captures the "true" nature, which it will never be able to do (because of its virtue of being a model) and hence all models are wrong. Semantics. Unless you disagree of course.
nzjrs 8y ago
It's funny, I thought the opposite. I was happy to read an explanation by an eminent and respected systems neuroscientist on hierarchy of computation, rather than the musing of an undergrad computer scientist on their first encounter with nature neuroscience.
- mjburgess 8y ago
  An ANN is just calculus with matrices that does not lend itself, by the mathematics alone, to any "neuronal" description which is ad-hoc and imposed from the outside. You can draw many computations in "neuronal" form, eg., a logistic regression. It's really just a way of diagramming math. "Computer" is an observer-relative term. There is no physical property of a system which makes it a computer. A "digital computer" is just a tool made of silicon which we use to aid computation (a goal we have). There are many tools (from an abacus to a waterfall) that we can use to aid in computation. "Computation" isn't anything other than a goal we have. To interpret the brain as engaged in it carries no information and says nothing explanatory. The sense in which a brain is a computer is the same sense in which everything is: a physical system whose state evolution can be used to aid in computation (but isnt: no one uses brains to compute).
  - TeMPOraL 8y ago
    Let's not go too far. When we talk about the brain being a computer, we mean it in a sense in which some μC/μP and related paraphernalias forming a computer inside your phone, or any other electronical device - that is, a component which takes all or most of the inputs, drives the device, and which if you rip out, you're left with a useless and dead machine. A rock and a waterfall perform computations in a theoretical sense if you look at them right, but there's also a different sense in which a bunch of op-amps in a circuit are a computer, a bunch of hydraulic logic gates are a computer, and a Raspberry Pi is a computer, but a rock isn't a computer. In that sense, human and animal brains are computers too. (I'm before my morning coffee so I apologize for not being able to name "that sense" properly.)
    - mjburgess 8y ago

carlsborg 8y ago

All models are wrong, some are useful.

feanaro 8y ago
Not all models are wrong, since some may be modelling exactly the aspects of importance and not modelling exactly those which are incidental and of no consequence.
- joesb 8y ago
  Then they are still wrong. It's just that they are wrong in the part that you don't care about.
  - feanaro 8y ago
    Is it wrong, or is it simply an instance of the fact that a model is not the thing it models? The use of the word wrong sounds wrong to me here. The wrongness should be about whether the model accurately, or just approximately, or not at all, shares with the modelled object that part of the behaviour we are interested in.
- danmaz74 8y ago
  The point is that no model of a complex real world phenomenon is ever perfect, so, you shouldn't try to create a perfect model. But not being perfect doesn't mean that a model can't be useful; among all the possible "wrong" models, you need to identify the one(s) which is useful, ie, which models well the aspects of importance to you.
  - feanaro 8y ago
    I realize all that. I'm questioning the wisdom of the standard manoeuvre of preemptively calling all models imperfect or wrong, though.
    - danmaz74 8y ago
      Not everybody realises all that, so I suppose the OP cited that quote to reinforce the point that ANN are a very useful, but very imperfect model of the brain. I cite it often enough, but usually it's in person, where I can see the reaction of the person I'm talking with, and explain if necessary.
- Rainymood 8y ago
  All models are wrong. The map is not the territory. We are arguing semantics now. The point you're trying to argue is that a model is "right" in the sense that it models whatever we wanted it to model. We argue that a model is "right" if it captures the "true" nature, which it will never be able to do (because of its virtue of being a model) and hence all models are wrong. Semantics. Unless you disagree of course.

nzjrs 8y ago

It's funny, I thought the opposite. I was happy to read an explanation by an eminent and respected systems neuroscientist on hierarchy of computation, rather than the musing of an undergrad computer scientist on their first encounter with nature neuroscience.

mjburgess 8y ago
An ANN is just calculus with matrices that does not lend itself, by the mathematics alone, to any "neuronal" description which is ad-hoc and imposed from the outside. You can draw many computations in "neuronal" form, eg., a logistic regression. It's really just a way of diagramming math. "Computer" is an observer-relative term. There is no physical property of a system which makes it a computer. A "digital computer" is just a tool made of silicon which we use to aid computation (a goal we have). There are many tools (from an abacus to a waterfall) that we can use to aid in computation. "Computation" isn't anything other than a goal we have. To interpret the brain as engaged in it carries no information and says nothing explanatory. The sense in which a brain is a computer is the same sense in which everything is: a physical system whose state evolution can be used to aid in computation (but isnt: no one uses brains to compute).
- TeMPOraL 8y ago
  Let's not go too far. When we talk about the brain being a computer, we mean it in a sense in which some μC/μP and related paraphernalias forming a computer inside your phone, or any other electronical device - that is, a component which takes all or most of the inputs, drives the device, and which if you rip out, you're left with a useless and dead machine. A rock and a waterfall perform computations in a theoretical sense if you look at them right, but there's also a different sense in which a bunch of op-amps in a circuit are a computer, a bunch of hydraulic logic gates are a computer, and a Raspberry Pi is a computer, but a rock isn't a computer. In that sense, human and animal brains are computers too. (I'm before my morning coffee so I apologize for not being able to name "that sense" properly.)
  - mjburgess 8y ago