Commentary on #illusions

Here I will ponder over things we can learn n understand by working of various illusions

And the bigger question-
What is REAL!?

1
Human eye has resolution of 576 MP camera
It's huge.
But limited!

We can 'see' visible spectrum bw 3800-7400 A°

Likewise Ears can "hear" sound bw 20-20K htz

Human brain works on 1 exaFLOP computing power (Billion Billion calculation/sec)

2
We have long heard that everything is in state of perpetual motion.
True, if we think of all galaxies continuously moving.
But sense of motion is relative.
It's not absolute.
All the more.. it's not SMOOTH as analogue but in waveform.

It's a series of static positions!

3
Human perception of motion is at threshold of 10-13 still-frames/sec.
Below this Eyes see them as INDIVIDUAL still images.
Above that sense of MOTION is kicked in!

Higher the frame rate...smoother the motion (avg >50 Htz)
This is called as Flicker Fusion Threshold

4
Here's 1st cheat code-Persistence of vision
It causes 1ms visual stimulus to perceive for 100-400ms
Very short multiple stimuli r perceived as single stimulus eg 10ms green flash of light immediately followed by 10 ms red flash of light perceived as single yellow flash of light

5
Myelinated nerves can fire @ 1k/sec
So human eye can THEORETICALLY "see" 2 "separate" visual stimuli @ 1ms apart or it can resolve 1000 frames/sec.
But PRACTICALLY avg person can detect 150 fps.
Trained pilots can resolve 220 fps easily.

6
For comparison, muscle contracts 10x slower than nerve
Fastest muscle in body is eye muscle.
Typical eye blink happens in 100-400 ms

Another comparison-
Fastest muscle movement in animal kingdom is by Dracula Ant jaw muscle.
It completes act in 0.023ms!
https://royalsocietypublishing.org/doi/10.1098/rsos.181447

7
In animal world, it's crucial to know immediate next position of ur predator's jaws/claws

In less violent world u'll still like to know accurate position of baseball thrown by pitcher at u

So visual system has grown predictive accounting for neural delays caused by processing

8
Here's 2nd cheat code-
Motion extrapolation

Visual system extrapolates trajectory of a moving stimulus into the FUTURE!

Refer to Flash lag effect illusion

And ponder over how real is what u r seeing if that is only abstract approximation, inferred on own, ahead in time!

9
It's like AI predicting next move of object by its motion, speed & trajectory

Instead of seeing things honestly/truly as they r, our eyes SEE what mind PRESUMES, is going to happen NEXT!

Reality goes for a toss!

M$ revealed a drawing app doing same

10
If correct pair(color/greyscale) of set of neurons r fired along with saccadic eye movements then there is perception of motion even when visual stimulus is static object.
This is 3rd cheat code-
Predictive coding
It's reproduced in deep neural network https://www.frontiersin.org/articles/10.3389/fpsyg.2018.00345/full

11
Libet experiment showed that b4 any conscious decision & its execution by motor phenomenon, a decision is formed in mind

This precedes 0.55 sec b4 visible muscle action & 0.15 sec b4 its conscious awareness
It can b recorded by EEG as electric impulse aka Readiness potential

12
Recent experiments have allowed his team to PREDICT visible outcome TEN sec in advance!
Brain needs to compensate delay for neural impulse travel(400km/hr) from sense organ to cognition centre. So few mSec compensation is expected
But TEN sec?

Mind is already made up b4 act

13
4th Cheat code:Observer

Looks like observer experiencing through sense organ makes up his mind (literally) LONG b4 'reality' is presented to it!

So how transparent/real is 'reality' which is conveyed to us?
It's not only modified but sometimes MADE UP
https://www.nature.com/news/2008/080411/full/news.2008.751.html

14
5th Cheat code: Neural modulation of perception

Continuous dynamic process which alters sense to info being transmitted by sense organs
It can b gain of function or loss/suppression/masking of data being carried from sense organ to brain.
It's discussed in contrast illusions.