image but as your eye reads well I'm saying and jumps from word to word,

the paragraph will appear to slightly, just

subtly, wave and boil. The allusion is called anomalous

motion. It's neat. But to say it's fun

is tautology because the word

illusion literally means to have fun,

to mock, to play with. But illusions aren't

just fun and games. They also teach us

about our brains. Anomalous motion,

for instance, demonstrates that our brains process

things at different rates and piece by piece.

After a saccade, a quick eye movement, higher contrast

elements are perceived sooner than lower contrast

ones. When arranged in just the right way, this delay is exploited

and your visual system only has one explanation.

Low contrast parts of the image didn't get processed later

because this myelinated machine is wrong but rather because the image

itself

must be moving. Akiyoshi Kitaoka's brilliant

"Out of focus" causes nearby neurones to disagree about the little slices they

each detect. Some see big changes

after a saccade and some see hardly any. This makes it difficult for our brains

to calculate and factor in the effect

of our own eye movements, so the image itself

appears to be moving. But illusions aren't just about

moving. They can also be

moving, poignant, significant,

practical. They can mean the difference between life and death,

like in nature or during World War I

as dazzle paint on ships. This form of camouflage doesn't conceal the object

but rather

makes it difficult for an enemy to ascertain its prey's

true shape and thus where it's heading

or how fast it's going. In 1955

the Soviet Union displayed their new Bison and Bear long-range bombers

at an air show. It looked like they had

a lot. Afraid of falling behind, the US ramped up production on their own

B-52 bomber. But the whole thing

was an illusion. In the Soviet's film of the air show

the same few planes had been flown past the camera multiple times

in formations that gave the illusion of them having more bombers

than they really did. By the end of the 1950s the Soviet Union

only had about 150 long-range bombers,

whereas the Americans, fooled

by the illusion, had built nearly 2,000

at a cost of 900 million dollars.

Architecture is full of examples of real-world practical

optical illusions. My favorite are Disney castles.

They appear huge but it's

forced perspective - a lie. The tops

appear further away from us because they are actually

quite tiny.

Illusions also tell us about ourselves culturally.

The Müller-Lyer illusion is classic.

The horizontal lines are all the same length but the bottom ones

appear longer to people from Western cultures,

familiar with our rules of perspective and man-made straight lines.

However, bushmen from Southern Africa and tribespeople

from northern Angola or the Ivory Coast aren't

fooled at all. Akiyoshi Kitaoka

is using optical illusions to discover glaucoma

earlier than current techniques can. And

anamorphic illusions are used to save lives.

They look weird from any perspective but one, from which they seem to pop out

defying the environment's actual shape.

Hoping to remind drivers to always pay attention

traffic safety organizations in West Vancouver, Canada placed a skewed

decal on the road. From the right perspective,

the perspective of the driver in this case, it becomes a 3D illusion of a child

you are about to hit.

Slow down. Brusspub has made some incredible examples of the 3D effect

such illusions can happen.

This object? Just an anamorphic projection.

Anamorphic illusions have also been used to safely practice

political dissent.

In 1746

supporters of the Stuart claim to the British throne

had to be quiet about it. It was treasonous.

So, sympathizers served things on

trays that looked like this.

Innocuous enough until only supporters

were around. And it was safe for someone to place a reflective

goblet or cylinder on the tray, revealing the tray's anamorphic secret a

hidden portrait

of their elicit love, Charles Edward Stuart himself.

The Encyclopedia Titanica lists descriptions

of everybody recovered from the Titanic.

It's quite macabre. Why was the iceberg

not seen until it was too late?

And why did the nearest ship - the Californian -

not come to the Titanic's rescue sooner?

Tragic questions whose answers might be

optical

illusions. The Titanic was sailing through conditions

perfect for mirages.

This theory points out that the Titanic sank

at the border of the warmer Gulf Stream and the frigid Labrador Current,

where the normal case of cooler air at higher altitudes

was inverted - a thermal inversion.

Now, because the temperature of air effects its index of refraction,

a thermal inversion means light bending

in a typical ways. If light reaches the eye

from higher up than usual, objects can appear to float.

Seriously. Like this ship off the coast of Australia.

A thermal inversion can also render objects completely unrecognizable,

hidden within a haze, like this ship(?)

Or like an iceberg.

Or a sinking ship in need of help.

The Delboeuf illusion may be causing

teeth to split and crack more often than they should

when dentists drill holes in them.

Doctor Robert O'Shea observed

8 practicing dentists and found that they were all drilling holes

that were too big, even though they knew the correct size

to be drilling.

Why? Well, it may be the same reason people

eat more food when they're given a bigger plate.

Objects appear smaller when enclosed by larger areas.

Holes of the same size may appear different sizes on bigger

teeth. Dentists may be deciding that correctly sized

holes drilled in the teeth need to be made larger,

not because they do, but because perception

is a tricky thing.

Illusions affect not only big ships and

teeth but also your future.

The End of History Illusion is our tendency to think of ourselves today

as somehow done.

Sure.

I went through a lot of personal growth and changes in taste

in the past, but today, who I am now,

this is pretty much the final me.

But that's not true.

Studies have consistently shown that people underestimate just how

different they will be, say, 10 years in the future,

even though they can easily point out how much they've changed

since 10 years ago. I like how Daniel Tomasulo puts it:

"We believe we are going to live, love,

and long for where, who, and what we are thinking about

right now. But the research says it just ain't so.

This too is a transient state."

Yogi Berra put it even more succinctly: "The future

ain't what it used to be."

Their advice

is don't imagine your future.

Look at other people and their experiences instead, take their advice.

Your imagination is just that, their experiences

are actual data. Well, of course,

it's not that simple. Which brings us to our final

illusion: The illusion of control.

Named by psychologist Ellen Langer, it's our tendency to believe we control the

outcomes of things.

We demonstrably don't.

It can help motivate us to not give up

and, in healthy people at a healthy level, it is

optimistic self-appraisal.

But it's a lie.

In one study, traders in the City of London's investment banks were shown a

graph

of a real time stock price and given three

buttons that secretly didn't do anything

to affect the price. But they were told the buttons might have an effect -

try them out, see what you can do.

Afterwards, the traders were asked to rate how much they felt they had been

able to control the stock price

with the useless buttons. And it turns out

the traders who reported the greatest sense of control over the stock price

were the ones who scored lowest on risk management tests

and, in the real world, contributed the least

to their company's profits and in terms of salary

made the least money.

It's kind of a bummer. The illusion of control is a nice feeling

but sometimes it's fine, sometimes it even pays handsomely to admit

you don't have control.

And as always,

thanks for watching.