Talk:Free energy principle

Citation [3]

In the introduction it says: "AI implementations based on the active inference principle have shown advantages over other methods.[3]".

This citation leads to a Wired article. I think a better source is needed. 134.184.26.82 (talk) 10:42, 10 July 2020 (UTC)

Typo in formula?

I suspect there is a typo in the formula:

$a(t)={\underset {a}{\operatorname {arg\,min} }}\{F(s(t),\mu (t))\}$

The parameter "a" of the argmin does not appear in the expression that it should minimize. — Preceding unsigned comment added by 193.171.142.191 (talk) 08:39, 21 October 2014 (UTC)

No typo

The sensory states are a probabilistic mapping from actions (and hidden states). See the definition for S and the Brain picture.

$s(t)=f_{z}(\psi ,a)+\omega$

So, actually:

$s(t,a)=f_{z}(\psi ,a)+\omega$

And you can start sweeping over parameter a if you like that, or in other ways consider that a impacts s. Especially if s is the perception of a belly when someone is trying to look at their feet. ;-)

Anne van Rossum (talk) 13:39, 4 January 2015 (UTC)

A funny little comment on Fristons models and priors

According to Karl Friston (see Friston 2010), all unconscious living systems have to maximize p(s│m) [with s: sensory state, m: model (or map)] in order to be able to live, i.e., to fight against dissolving or disintegration.

Interestingly, in this implicit equation above (with a probabilistic function or map!), m is given or presupposed, as is the separation between m and s.

However, only a "conscious" living system (e.g., I) "knows" of "having" "maps" (including differentiated "sensory maps") and that I may be a "map-maker". But even "conscious" living systems have to live, so even for them the equation above still holds, albeit now with a slight difference: maximize p(s*│m*) AND p(s│m), and that is why scientists have had to make up artificial experimental tests in order to test their "conscious" maps (e.g., functional hypotheses, etc.).

It is clear that the body (including "genomic maps" "inherited" from "the past") is far better at this optimization process than scientists, because the body does this constantly and full time (whereas most scientists only work part time nowadays). That is why professional soccer players (i.e., unconscious Bayesian machines) are so favoured and payed in "our" world -- because they have (nearly) "made it" on an unconscious level, whereas understanding and testing scientific maps or models may be much more difficult (and only in existence for some 400 years or so).

But all these probabilities mentioned above are smaller than 1, so the only option for scientists (given a messianic prior) is to wait until Judgement Day (where the whole truth will become unveiled anyway) while working and earning money endlessly...

Only for mapologists -- having become "conscious of" (i.e., having been able to map) all maps and biases and priors WITHOUT having to "act" upon some seemingly "outer world" -- the following equation holds:

p(m│m*) = p(m*│m) = p(m│m) = p(m) = p(s*│s) = p(s│s) = p(s)

This means: having reached the horizon (where "life" ≡ "death" ≡ Nirvana ≡ Samsara ≡ COSMOS ≡ I )...

FRISTON, Karl J. (2010): The free-energy principle: a unified brain theory? Nature Reviews Neuroscience 11, 127-138.

— Preceding unsigned comment added by 2A02:1205:C68D:47C0:2052:B3F5:1909:DEB1 (talk) 10:22, 16 June 2014 (UTC)

Too esoteric

This is not close to appropriate for a general audience. I'm a neuroscientist, have written mathematical papers about bayesian inference, information theory, and this is gobbeldy-gook to me. All due respect, but this needs to be written in a language that isn't just for True Believers. Comment from May 2017 by User:152.16.191.113

Agreed. This might be a good starting point: https://www.youtube.com/watch?v=NIu_dJGyIQI -- Akvadrako (talk) 17:59, 31 March 2018 (UTC)

I agree too. I'm a PhD philosopher and clinical psychologist, and can make close to zero sense of this page. I also find that when I read papers in this area they are chock full with jargon. Mentalistic metaphors (talk of predictions, errors, models, representations, hypotheses, inferences etc) are used, presumably to try to make the raw neuropsychology less unapproachable, but they are rarely cashed out in a perspicuous way. Furthermore one is always left with the worry that they are not always meant as metaphors - as if the brain really were magically supposed to be involved in making 'inferences' or 'hypotheses' or in generating 'percepts' etc. (Helmholtz might not have known better and we can forgive him; today, though, it's not ok!) Please please please could someone who is cognisant of this area rewrite the page for us?! 84.68.66.212 (talk) 09:54, 8 July 2019 (UTC)

I'm from the physics side of things. Here's a quote from Friston 2003: [1]

"EM provides a useful procedure for density estimation that helps relate many different models within a framework that has direct connections with statistical mechanics. Both steps of the EM algorithm involve maximising a function of the densities that corresponds to the negative free energy in physics"

Here's a book review concerning a book titled "evolution as entropy": [2]

"Since C. E. Shannon introduced the information measure in 1948 and showed a formal analogy between the information measure ($-\sum p_{i}ln_{2}(p_{i})$ ) and the entropy measure of statistical mechanics ($-k\sum f_{i}ln(f_{i})$), a number of works have appeared trying to relate "entropy" to all sorts of academic disciplines. Many of these theories involve profound confusion about the underlying thermal physics and their authors use the language and formulae of the physical sciences to bolster otherwise trivial and vacuous theories. "

As far as I can tell, the "free energy principle" is based on this confusion. Specifically, two formulas look very similar, so there's a strong intuition that they must have some deep connection. The mathematical analogy is obvious, the conceptual connection is actually rather dubious. The main Wikipedia article is entropy in thermodynamics and information theory, which addresses the controversial assumption of treating them like the same concept. $\langle$ Forbes₇₂ | Talk $\rangle$ 03:48, 8 February 2020 (UTC)

Agreed, I work in active perception and bayesian inference. This is basically nonsense and presents a very narrow and specific view of the field of active perception and inference, specifically one that is basically not workable for any solution which someone might want to implement.

Type signature of definition section unclear

In the definition section, it states the type signature of some of these quantities in an unclear way. For example it states "Hidden or external states $\Psi :\Psi \times A\times \Omega \to \mathbb {R}$" But if $\Psi$ is a function, then it cannot also be a set. The topic is already confusing enough so I suggest using a different symbol for the set $\Psi$ than for the distribution $\Psi$.

From the lead of the Wikipedia article Function (mathematics):"A function is uniquely represented by the set of all [its] pairs (x, f (x))..." So, indeed, a set can be a function (in the appropriate context). (copy and pasted April 25, 2022).(I inserted [its] for clarity here).(whether that mathematical fact is appropriate here (in the article's gobbledygook), I can't say.) (also note that the mathematical term 'distribution' needs careful attention (lol, irony intended) since its definition differs depending on context (and I'd guess is used/confused both as it is in statistical mechanics and in finite-State automata/computer science/coding).207.155.85.22 (talk) 02:29, 26 April 2022 (UTC)

The definition of the type signature is definitely unclear, and there are some other issues here, including an incompatibility between these definitions and the examples in the schematic. This needs to be fixed really. Alpacaswamp (talk) 11:32, 23 May 2022 (UTC)

Time average is action?

Near the end we read "Finally, because the time average of energy is action..."

Shouldn't that be "the time integral of energy is action..."? Wouldn't the time average of energy just be energy, not action? Vaughan Pratt (talk) 18:33, 11 April 2021 (UTC)

Definition

The Definition section is awful. 1. $\mathbb {R}$ usually means the set of Real numbers. That doesn't make sense here. 2. <symbol>:<expression> → <symbol> is used as the core structure of the four of the clauses and A$\times$B is used 6 times. Without explanation! 3. I don't understand S: $\Psi$$\times$A$\times \Omega$ → $\mathbb {R}$ and A:S$\times$R→$\mathbb {R}$. Are these circular? How can you define S in terms of A and A in terms of S??? 4. the (Bayesian?) expressions p(s,$\psi$ |m) and q($\psi ,\mu$ |m) are two types (?) of "density" Again, not defined term(s). 5. $\omega$ is described first but never again used. 6. if the "generative model m" is a fundamental building block, then shouldn't it be part of the "tuple"? 7. And shouldn't there be a clear link to its meaning? 7. finally, a trivial point but I assume s $\in$ S should be included like $\psi$ and $\mu$ are.207.155.85.22 (talk) 04:33, 26 April 2022 (UTC)

Yes the definition section needs to be fixed but is there anyone editing this page who really understands the issues? Alpacaswamp (talk) 11:34, 23 May 2022 (UTC)