Total recall: some people can remember every day like it was yesterday

This teenager remembers the ID number of every garbage truck he has ever seen. Graham Duggan

In the Nature of Things documentary The Memory Mirage, we learn that even our most precious memories may not be as accurate as we thought. Our brains change our memories, altering details and adapting them over time.

But what if you could remember everything from your life — from what you ate for breakfast every single day to how you felt during every painful moment? While most humans have limitations around recalling and retaining details from their past, there are some people who have unusual and seemingly perfect powers of memories.

“I remember everything”: HSAM

Teenager Tyler Hickenbottom has a rare condition known as ‘HSAM’ (Highly Superior Autobiographical Memory) and is featured in The Memory Mirage. It allows him to remember every day of his life like it was yesterday.

The condition was first identified by neurobiologist James McGaugh when a woman named Jill Price approached him with questions about her unusual memory abilities. When offered a particular date, Jill was able to recall what she did that day and what day of the week it fell on, with incredible accuracy. She became the first person to be diagnosed with HSAM.

Since then, more than 50 other people have been identified as having HSAM, including Taxi actress Marilou Henner. What is the secret to their incredible memory?

Based on MRI brain scans, the parts of the brain associated with autobiographical memory creation are enlarged in HSAM subjects. Researchers know that these same brain areas are also linked to compulsive behaviours, something HSAM subjects exhibit. Hickenbottom, for example, remembers the ID numbers of every garbage truck he has ever seen, records them on video and shares them on YouTube. Other HSAM’ers are known to be germaphobes or to compulsively categorize their closet.

Researchers aren’t sure if the brain structures are the cause — or the result — of the condition, Some wonder if HSAM individuals share the same memory capabilities as the average person, only they have a much better way of retrieving them.

Photographic memory

The term “photographic memory,”— also called eidetic memory — describes the ability to recall visual information by taking a quick mental snapshot that can be reviewed later. But scientists disagree about the existence of true photographic memory and argue whether or not humans are capable of creating mental snapshots with perfect precision.

That doesn’t make eidetic memory any less impressive. Stephen Wiltshire is a British artist who draws incredibly detailed to-scale cityscapes on giant canvases. As a child, he was diagnosed with autism and was unable to communicate verbally. At the age of five, Stephen began drawing — the only pastime he enjoyed. It became apparent that drawing was his way of communicating with the world. Today, Stephen’s art is highly prized, with some of his pieces fetching more than $20,000.

Wiltshire took a 20-minute helicopter ride over New York City, then sketched a 5.5-metre long aerial scene over seven days — all from memory. His recreations are so detailed, buildings even include the correct number of windows. 

Kim Peek was the inspiration for Dustin Hoffman’s Rain Man character. According to his father, Peek was able to memorize things from the age of 16 months and read and remembered thousands of books. He scanned the left page with his left eye, and the right page with his right eye and could finish a book in an hour. According to the New York Times, Kim could recall the contents of at least 12,000 books.

Memories in our DNA

Within our own lifetimes, our memories change and re-shape with time. But perhaps we all have the ability for total recall, just not in our brains — over generations, we may be able to retain very old memories from our past ancestors.

Phobias are defined as “an extreme or irrational fear or aversion to something.” Most are fears of something harmless, like open spaces, or spiders; but new research suggests that they may not be irrational at all.

Human learning is passed on through teaching, from generation to generation. A recent study in Nature suggests that we may genetically inherit memories from our ancestors. Stressful or traumatic events can cause chemical changes in our DNA, and these changes can be passed down to our offspring, affecting their brains — something scientists call “ancestral experience.”

To prove this, researchers created a fear of cherry blossom scent in mice. After allowing those mice to breed, their offspring showed the same fear response to the scent, even though they had never been exposed to it. This fear response continued down through generations as the offspring mice had babies of their own.

We change our memories each time we recall them, but that doesn’t mean we’re lying
Partial recall: Why we can’t trust our own memories

Although this hasn’t conclusively been documented in humans yet, researchers believe irrational fears could be a defence mechanism, memories that were burned into the DNA of our ancestors long before we were born.

For more about human memory watch The Memory Mirage.


Available on CBC Gem

The Memory Mirage

Nature of Things