
Brains Speed Up Perception by Guessing What’s Next - pseudolus
https://www.quantamagazine.org/brains-speed-up-perception-by-guessing-whats-next-20190502/
======
frereubu
This ties in quite nicely with Karl Friston's Free Energy Principle:
[https://www.youtube.com/watch?v=NIu_dJGyIQI](https://www.youtube.com/watch?v=NIu_dJGyIQI)

There are so many strands of neuroscience that show predictive coding now.
There's a really nice example in the use of common vs unusual words in
sentences. If you're using fMRI to scan someone while they read these two
sentences:

The jam on the motorway made everything slow.

The jam on the motorway made everything sticky.

You'll see a flash of activity when people read the word "sticky" rather than
the more common word in that context "slow". The theory is that when
everything in the sentence proceeds as predicted there's very little need to
update prior expectations, but when you come across something that goes
against previous predictions it's a signal that something needs to be actively
thought about.

~~~
ta1234567890
Cool! This sounds similar to koans: "a paradoxical anecdote or riddle, used in
Zen Buddhism to demonstrate the inadequacy of logical reasoning and to provoke
enlightenment."

If you explore the meaning of language enough you'll realize it doesn't really
make sense.

Everything is based on context and assumptions that we take for granted when
communicating. But if you dig deep enough (and it's really not that deep
anyway), you'll notice that pretty much anything you say or write can be
interpreted in multiple different ways, which means there's no one absolute
meaning to any expression of language.

Meaning comes from interpretation, which is subjective and unique to the
person doing it.

Interesting exercise: for a day or a week, make an effort to think how
anything that someone else says to you is actually true - asume they are
always right and think about how to justify it. It's really amazing, at first
it's really hard, but then you discover you can always just interpret what
they say in a way that fits your views.

~~~
soulofmischief
I think you can make unambiguous sentences: "I walked one mile today." Unless
context _specifically_ indicates the very rare possibility that _walked_ is
personal shorthand for another activity, it's a pretty unambiguous statement.

~~~
p1necone
I can think of two different ways to interpret that sentence.

1: They went for a walk as a single activity on top of their regular daily
walking, and that walk was a mile long.

2\. They walked a total of 1 mile throughout the entire day, including regular
walking around the house/office etc.

I do agree with the sentiment though, there definitely are plenty of
unambiguous sentences you can say in everyday conversation.

Perhaps "my refrigerator is currently powered on" is an arbitrary example that
works.

~~~
soulofmischief
That's pretty good. But then knowing that ambiguity, I could craft a statement
like, "I walked a mile on the treadmill today."

~~~
ta1234567890
Exactly, and if you keep going, you'd notice you need each time a longer, more
precise description, which at the same time, paradoxically, opens the door for
more ambiguity.

In that example, the first context is English language, then knowing who I is,
then what a mile is, and a treadmill and today. All of those are contextual.
Even mile. How long is a mile? Like any physical measure, it actually varies,
because it is defined relative to something else which varies. The meaning of
English language has also varied over time, that sentence might not make any
sense to someone reading it in 20 years. And then when is today? May 7, 2019 -
which is also a relative measure of time and not even that precise.

And then finally, what if you were lying? Did you really walk a mile today?
How can I be sure? And how can you be sure I understand the same meaning from
the words you say or write?

~~~
soulofmischief
I understand where you are coming from, but a lot of what you just presented
isn't actually relevant to the topic of ambiguity from lack of context in
language. Some of it just doesn't apply. Allow me to explain...

> the first context is English language

Let's ignore this context. If you don't understand English then you shouldn't
be expected to understand an English statement regardless of context.

> How long is a mile?

That depends on what time and space you are in. But that's ok. All such
measurements are relative and defined by non-natural constructs. But we can be
realistic and assume a mile is whatever _our government_ has decided.

When I tell you "I ran a mile", I'm not telling someone in Australia I ran a
mile. I"m telling _you_ that. If we are speaking over the internet it might
complicate things, but we only have to resolve the meaning of _mile_ once for
our relationship, and all proceeding discussions will use this meaning.

I would argue that this makes the word _mile_ unambiguous in the sense that
you are saying. If we had to assert _each time_ what I meant by a mile, then
that would be ambiguous.

> that sentence might not make any sense to someone reading it in 20 years

Evolution of language is a separate phenomenon. We don't need to consider
that. Only what the language means _today_ right now as I use it. That's the
utility of language. For older English texts, we have literature which matches
our common vernacular to the vernacular of the time. Foreign translations are
out of scope for the same reason listed above. Since we have mappings between
today's English and yesterday's English, I would again argue that this is not
a source of ambiguity.

> And then when is today? May 7, 2019

That doesn't have anything to do with language. That is a chronospacial
coordinate. It represents a certain degree of completion of our orbit around
the sun. It isn't a measurement of time at all. It's only relative in the
sense that all time and space measurements are relative to the spacetime
coordinate of the Big Bang.

Time is inherently a _relative concept_. We don't have time unless we are
comparing (relating) two different frames. We define one in terms relative to
the other (motion, state, etc). In a single, non-relative frame of reference
time just doesn't exist.

> And then finally, what if you were lying?

Again, this has nothing to do with language. You aren't trying to guess what
I'm _thinking_ , you're trying to understand what I'm _saying_. That's what
language parsing is about. Discussion of motivations, misdirection, etc. is
irrelevant.

~~~
ta1234567890
Interesting. All of the above rebuttals are basically: ignore this because
it's context and should be obvious.

Well, that's the problem. It might seem obvious to you now, but it is not
obvious to everyone all the time, which is what makes any statement ambiguous.

Additionally, I don't know the purpose of what you are saying. For example,
you might say you ran a mile because you wanted to express you were tired, or
because you wanted to imply you are healthy, or who knows why, it is
definitely not clear from the statement alone what you wanted to convey, which
is the main problem.

We feel something internally and then we try to express that in words, hoping
that those words will mean the same to the person perceiving them. That
process is highly suceptible to noise in many forms, like the other person not
hearing you correctly, being distracted, being stressed out, or maybe they
speak a slightly different version of your language and some of the words or
expressions mean something a bit different to them than to you.

In the end, any statement doesn't have meaning by itself, it only acquires
meaning when someone interprets it and understands it in a certain way. That
is always a subjective process.

~~~
soulofmischief
Honestly I feel like we could have a very deep conversation about this because
I certainly agree with a lot of what you're saying.

Language is certainly subjective, but I would argue that we can make certain
concessions on what context truly is "obvious" and what isn't. And I think the
matter of what level of precision is acceptable enough to consider a statement
or idea "understood" is up for debate and is also contextual.

At some point, any extra information is just that, extra information. The core
idea may have been expressed fully, even if there are certain small
ambiguities or if the listener wishes to draw insight from the statement
beyond the basic sentiment expressed.

~~~
ta1234567890
Completely agree with you.

Language is an incredibly useful tool and it works very well for most of our
daily lives and many important things without thinking too much about it.

It's just very interesting to me to see how something that seems so solid, in
some ways is much more fluid and fuzzy.

Thank you for keeping this thread going, really enjoyed discussing this.

------
erikpukinskis
This reminds me of the work John Carmack did when he was writing QuakeWorld,
which in 1996 was quite playable __on a 56k modem! __He started off predicting
300ms of lag on the client side, but it was too glitchy when the correction
came in. He landed on a more conservative strategy, and his writeup is a
touchstone of Computer Science lore for me:

[https://fabiensanglard.net/quakeSource/johnc-
log.aug.htm](https://fabiensanglard.net/quakeSource/johnc-log.aug.htm)

I wonder if you could design a game around this by drawing BOTH the predicted
motion and a ghost image of the last known verified server position of
players, and then deliberately introduce 500ms of latency. The gameplay would
then be about tricking your opponents into thinking you were going somewhere
you're not.

~~~
lqet
How much of this improved network code made it back into the original Quake
engine, and therefore into Half-Life 1? To this day, I have yet to find a
multiplayer engine for an ego shooter which feels as perfect as the one in HL
1. For lack of a better description, the Half-Life 1 (and mods) multiplayer
game-play just felt (and still feels) _crystal clear_. This has to be one of
the major reasons why Counter-Strike became so big.

~~~
soulofmischief
From Wikipedia [0]:

 _The engine also reuses code from other games in the Quake series, including
QuakeWorld, and Quake II, but this reuse is minimal in comparison to that of
the original Quake._

[0]
[https://en.wikipedia.org/wiki/GoldSrc#Development](https://en.wikipedia.org/wiki/GoldSrc#Development)

------
teeray
> Imagine picking up a glass of what you think is apple juice, only to take a
> sip and discover that it’s actually ginger ale. Even though you usually love
> the soda, this time it tastes terrible

Even brains aren’t safe from speculative execution vulnerabilities

~~~
HiroshiSan
This happened to me drinking soda water, I thought it was just regular old tap
water, went to take a huge sip and immediately spit it out in disgust.

I normally hate soda water, but that time I especially hated it.

~~~
cr0sh
If you wanted to mess with a person, other substitutes could be vodka or white
vinegar.

Note you could do the same for a vodka drinker; it gets more interesting if
they're already in the bag...

~~~
harry8
I once saw a man get another man falling down drunk at a residential college
(frat house equiv?) bar serving him water while being convincing it was 100%
pure and tasteless alcohol from the chemistry lab. (De-ionised water,
probably). Served from a conical glass beaker with hushed tones, "I don't want
to get kicked out for this so don't tell anyone." The full con-job. They were
and are friends and it was utterly hilarious. The drunk guy was not insulted
nor upset in the aftermath and still tells the story.

Falling of the stool, uproariously laughing drunk. Someone else who was in on
it (I wasn't, I was getting drunk for real on beer) produced an old Nintendo
Game 'n watch where the water drunk guy got the top score of any of us.
Apparently being drunk like this didn't affect his reaction time at all. No
hangover, Immediately sobered up post-reveal and claims he felt totally drunk.
(Then almost immediately drank a family sized rum or something - kids those
days, sheesh).

It'd be great if you could get that enjoyable drunkeness feeling like so as
easily as by pouring booze down your neck...

"Ladies and gentleman, pivot your startups, go!"

"We're the world leaders in getting neural nets drunk, then making them
classify with a hangover..."

Yeah I'm sorry, hasn't been a great week...

------
kranner
I’ve noticed during meditation on external sounds that for any repetitive
sound, my brain immediately starts reproducing the sound internally, and then
stops paying attention to that external sound and starts scanning the
background for other sounds. This is the case for anything from air
conditioner whine to birdsong. The meditation then becomes to interrupt the
cached reproduction and really listen to every sound, including repetitive
ones, forcing my brain to expect surprising variations in the same sounds if I
can listen really closely.

~~~
mruts
My wife always play guitar and even after she stops I hear the song she was
playing for the rest of the day. It’s very unnerving. What other parts of
reality am I just filling in?

~~~
rzzzt
People actually disappear when you aren't looking, to lower simulation
overhead.

~~~
sk0g
So aggressive culling will solve global warming and food shortages.

Dibs not being tasked with building the culling into earth's engine!

~~~
hawaiian
Unfortunately, this will not work. The simulation just deletes food and
materializes CO2 and waste matter in line with expectations.

------
jedberg
Although they just discovered the mechanism, we've known that this happens for
quite some time. It's something you can take advantage of in UX design, for
example, because if you provide a subtle queue before something new happens to
trigger the brain, the new thing will be perceived faster.

~~~
noobiemcfoob
They have known it too. The first cited experiments in this article were done
in 2012. I wonder how long it's existed as a theory in neuroscience.

~~~
Phemist
In cognitive psychology, I've worked with a method known as "masked priming"
[0], which is relatively well-known in the field to influence reaction times.
Reaction time is a complex measure as it includes both "processing speed" as
well as physical reaction times. The "prime" is considered subliminal, as one
would not necessarily notice it being presented (although the mask definitely
is noticeable). Interestingly, at short enough time scales, e.g. 16 ms
duration times, the effect of the priming reverse, and it makes reaction times
increase[1].

[0]
[http://www.u.arizona.edu/~kforster/priming/](http://www.u.arizona.edu/~kforster/priming/)
[1]
[https://link.springer.com/article/10.3758%2FBF03196307](https://link.springer.com/article/10.3758%2FBF03196307)

------
Crinus
Yeap, this is why sometimes when i read some text, press press Space to scroll
the page my brain has already started "reading" from the top of the page and
then gets confused when the page has hijacked space and it didn't really
scroll, the words do not make sense as they're not a continuation of what i
was reading so i take a second to reorient my eyes around the page to realize
what is wrong.

------
ben7799
This is hugely noticeable playing/practicing/learning music.

Just yesterday playing guitar.. I was fighting playing the wrong note cause my
brain was guessing that was the next note because so often in so much music it
would be. It was something like 3 notes that are in a particular scale and my
brain really wanted to play the next note in the scale instead of the correct
next note.

In all activities our brain internalizes how to do things and we can suddenly
do them without having to think consciously about how it's happening.. huge in
sports and anything with motor skills... music, video games, etc, etc..

~~~
ThrustVectoring
Guessing what's next is the only way the brain knows how to play music. If you
aren't hearing the music you want to play correctly, you _cannot_ play it. A
lot of music education gets things pretty messed up by ignoring this factor.

Highly relevant to all this is Hal Galper's approach to jazz education.
Example:
[https://www.youtube.com/watch?v=y_7DgCrziI8](https://www.youtube.com/watch?v=y_7DgCrziI8)

~~~
mamon
In similar fashion people that are deaf and cannot hear their own voice
eventually start speaking with strange manerisms, too loud, to quiet, weird
intonation, etc. But I don't think that's about predicting what comes next,
it's more about feedback loop allowing you to control your movement better.

------
pedro_hab
I've seen something like this with speech.

\- I have some accent when speaking english but not much. \- Some colleagues
from my home town have much stronger accents.

When they speak some words in weird ways I find that american colleagues just
understand and move on.

When I speak a word in a weird way they'll either laugh, bc it is funny, or
just be confused.

I think its because they are paying more attention to my colleagues with
stronger accents because they know they have to.

But with me they'll be more relaxed and get caught off guard when I pronounce
words wrong.

------
wpietri
How timely! I recently attended a nephew's soccer game. Having never played, I
didn't really know what was going on. It seemed to me that I had a much harder
time perceiving what happened; I was forever asking someone to tell me what
they saw, even though I was looking at the same thing. If a lot of perception
is predictive based on previous experience, it makes sense that I felt like I
was half blind.

~~~
ThrustVectoring
Your perception system doesn't report some sort of fixed reality. It surfaces
the information that is most relevant to you and what you want to do. For
example, better batters playing baseball will literally perceive the ball as
larger.

------
lqet
Why is this page displaying a 404 for roughly a second before loading the
actual page? Is this part of the point made by the article?

------
dmitryminkovsky
Wow this explains a lot. I think this is a huge subconscious source of anxiety
for me.

~~~
theoh
More generally, it's becoming accepted that a major part of brain's function
is predictive, because it's an important aspect of closed-loop control.

[https://en.wikipedia.org/wiki/Predictive_coding](https://en.wikipedia.org/wiki/Predictive_coding)

------
rosser
And then we so often get mad at the world for our own guess not being
accurate...

------
npcdevops
Like Meltdown and Spectre for your brain... hard to exploit, but not
impossible.

~~~
bitwize
Indeed, albeit Spectre exploits for the brain are so common that we even have
a short word for them: we call them jokes.

~~~
HeWhoLurksLate
Or misleading legalese, plays on words, or pens.

------
daenz
CPUs have this as well, for increased performance
[https://en.wikipedia.org/wiki/Branch_predictor](https://en.wikipedia.org/wiki/Branch_predictor)

~~~
basetop
Would caching also be a form of "guessing" what's next? Cache hits could be
considered guessing correctly and while cache misses is guessing incorrectly.

------
curious_fella_
Jeff Hawkins introduced this in 2004 "On Intelligence":

[https://en.wikipedia.org/wiki/Memory-
prediction_framework](https://en.wikipedia.org/wiki/Memory-
prediction_framework)

------
eli_gottlieb
CTRL-F "predictive coding", nothing found, what the hell, Fontanini et al?

------
emiliobumachar
Related: Surfing Uncertainty

[https://slatestarcodex.com/2017/09/05/book-review-surfing-
un...](https://slatestarcodex.com/2017/09/05/book-review-surfing-uncertainty/)

[https://news.ycombinator.com/item?id=19861929](https://news.ycombinator.com/item?id=19861929)

------
baybal2
Branch prediction... Real world cache misses can be much more painful though

------
noiv
Is this any different from branch prediction?

------
ycombonator
Branch prediction

