Mixed-Up Memories


Just a minute of physical exertion can seriously impair a person’s memory of the threat that triggered it, says a new study.

When we undergo a strenuous task, such as a chase or a fight, immediately after witnessing an event, we have much less ability to remember the event’s details than if we’d taken time to process what we’ve seen.

This calls the concept of eyewitness testimony into serious question. As I’ve written here and Jonah Lehrer has written here, our memories aren’t nearly as static as we might like to think. In fact, each time we recall a memory, our brains piece it together and play it out for us anew – Lehrer uses the analogy of a play, as opposed to a movie – then record the version we just saw as “the memory.”

As I explain in our first video, our brains don’t store information in anything as static as a file, but in dynamic, ever-evolving connections between patterns of neural activity. That means consciousness itself is less like a computer program and more like a symphony – something that’s never the same from one moment to the next.

And then there’s the fact that our brains have a knack for filtering out details they don’t think are important – as in the famous “basketball” video.

What all this means is that our brains are evolved to predict a lot of things accurately, but not always to remember so accurately. In other words, our nervous systems evolved to help us deal with new challenges as efficiently as possible, rather than to preserve a perfect picture of the past.

Remember when this memory mix-up was the biggest deal in the entire Western world?

A team led by Lorraine Hope of the University of Portsmouth found that out firsthand, the journal Psychological Science reports. The researchers selected 52 healthy police officers (42 men and 10 women) and gave them a “briefing” with lots of details about armed robberies that had recently happened.

Then some of the officers went through a strenuous bag-punching workout while others watched – and presumably while the researchers cranked up “Eye of the Tiger” and rocked out.

When the officers were then sent to arrest a “target individual” based on the descriptions of the robbers they’d heard earlier, some major problems became apparent:

Participants who completed the assault exercise showed impaired recall and recognition performance compared with the control group. Specifically, they provided significantly less accurate information concerning critical and incidental target individuals encountered during the scenario, recalled less briefing information, and provided fewer briefing updates than control participants did.

In other words, officer’s who’d gone all Rocky on the bag had less accurate memories, remembered fewer details, and checked in less frequently with H.Q. In fact, the researchers found that officers who hadn’t undergone a strenuous workout remembered more than twice as many details about the suspects.

Oh, and let’s not forget:

Exertion was also associated with reduced accuracy in identifying the critical target from a lineup.

It doesn’t take a trained psychologist to recognize that this is just as much a danger for victims of crimes as it is for police officers. In fact, the researchers point out that these memory impairments could affect anyone who works in a stressful setting, whether it’s the military or just a high-pressure office.

So, while I’m very glad we have police officers who do their best to identify suspects accurately, it’s still important to remember that they’re human, just like the rest of us. If we really want to make sure our memories are accurate, it’s probably a good idea to have multiple independent sources check our facts in different ways – which is why scientific papers are peer-reviewed and court records are public.

As for me, I’ll stick with Wikipedia…well known to be the most unchangeable source in human history.

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2 Responses to “Mixed-Up Memories”

  1. Micah says:

    Regarding your first video, actually scientists do have a plausible argument for where and how memory is stored in the brain.

    “Stuart Hameroff of the University of Arizona demonstrate a plausible mechanism for encoding synaptic memory in microtubules, major components of the structural cytoskeleton within neurons.”



  2. […] at all – our brains create them anew each time we recall them, and they change more and more with each performance. And not only that – study after study has proven that much of […]

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