Back in Ancient Greece, having a good memory was a sign of intelligence.

Memory was an art – orators or public speakers would give long speeches with unfailing accuracy, without the aid of others or notes.

Did I get that right?

Do you have a copy of the script?

Thanks.

Oh yeah!

Greek memory techniques continued to be popular throughout the Middle Age, where monks and scholars committed entire religious texts to memory.

In the past 100 or so years, we started to think of memory more scientifically.

n the early 1900s, when scientists were describing what our memory is like, they compared it to things like... A tape recorder.

Or even a filing cabinet.

And even a series of photographs.

They’re interesting analogies, but the nature of memory is far more complex.

First, I think we should explore how memory works.

This feels like a good place to start.

So there are two main types of memory.

One is declarative memory, your memory for facts like a phone number or dog breed.

This is different from procedural memory – your retention of a skill, like riding a bike.

It’s your procedural memory that knows this is a pen, and how to use it.

When we form declarative memories, the information travels to the hippocampus before it’s consolidated and permanently stored.

And when we form procedural memories, they rely on other areas – the cerebellum and the basal ganglia.

Of course, the type of memory the Ancient Greek people valued is declarative memory – your ability to recall facts and information.

And pushing the boundaries of declarative memory still fascinates us today.

Children memorise pi to tens of thousands of digits.

The memory champion Dominic O’Brien memorised 54 decks of cards after seeing them only once, in sequence.

That’s 2808 cards.

But the tricky thing about memory is that, we tend to lose memories.

It's in our nature to forget.

Do you know what page we're on?

Hmm.

So, the neurologist Oliver Sacks once wrote, “We, as human beings, are landed with memory systems that have fallibilities, frailties, and imperfections—but also great flexibility and creativity” It’s like a big paradox of our biology; that the one thing that controls all of our ideas and actions – our brain – can be manipulated by itself.

Our memories are vulnerable to ideas that come in after events have happened–it’s called “post-event information”.

These ideas, that are false, can be integrated into our brains so we think we remember them, when they actually didn't happen.

Our memories can change.

The American psychologist Elizabeth Loftus started her career investigating how human memory works in the real world.

She had this idea that vivd memories could be implanted in your mind when they actually didn't happen – when they were false.

So she did this study where she recruited subjects and talked to them about a time that they became lost in the mall when they were a child.

Following this, twenty five percent of those participants believed that they actually got lost in the mall – They even fabricated detailed memories around this idea.

It's concerning... American psychologist Rosalind Cartwright once wrote, “Memory is never a precise duplicate of the original… it is a continuing act of creation”.

And one of the reasons we can create new memories is because we kind of lose old ones.

It’s in our nature to forget.

For a long time, psychological theories try and make sense of why we lose our memories.

Decay theory suggests that over time, we can't retrieve memories because traces of them fade away and eventually, they disappear.

Interference theory suggests that when we form a new memories that's pretty similar to an existing one, it interferes with our ability to recall that existing memory.

Scientists have even found that walking through doorways causes us to forget things – like what we walked through that doorway to do.

Our physical change in location causes a new, location specific memory to be created.

It interferes with our old memories and those thoughts are lost – interfered with – in the transition.

But there's an upside to forgetting!

Our ability to lose information keeps our brains flexible so they can absorb new things.

If we didn’t forget, we’d recall all kinds of random information and I wouldn’t be able to focus on you.

When you think about it, you’re shaped by your memories, they're your collective experiences that you’ve had throughout your life.

And in a way, your memories are also shaped by you.

Why did I come out here?

Oh yeah.

Right.

Man this looks familiar.

Could you hold this for a sec?

This reminds me of something.

Back in Ancient Greece –