Do You See What I See? Kids' Visual Memory Works In Mysterious Ways

Working visual memory in kids works differently from adults.Neuroimage, via John Spencer

When kids look around, how much are they taking in about the objects that surround them? Scientists have recently devised new ways to peer inside little kid brains and figure out how their visual working memory works. They found that although young kids use the same parts of the brain to record visual objects in the world, they use those parts in a different way.

In adults, studies show that visual working memory maxes out at about 3 to 4 objects – meaning that adults can remember the orientation and color of just a handful of objects at a time. But no one knew how the same process worked in brains that were still developing.

The trouble with brains

Just how does someone go about getting an image of young kids’ brains? fMRI, which measures blood flow, requires subjects to hold still for a long time inside a claustrophobic and noisy tube – not easily achievable for a 3 year old. EEG can measure real-time resolution but doesn’t have much accuracy when it comes to location in the brain.

John Spencer, a psychology professor at the University of Iowa, used a technology called fNIRS to examine what kids see. fNIRS, he says, offered a signal that was as good as fMRI to showing the precise location of the brain’s firing signals. It didn’t require inserting kids into a metal tube. The technology only penetrates about 2 centimeters into the brain, making it ill-suited to thick-skulled adults but perfect for smaller kid brains.

“When some part of your brain is actively engaged in a task, that part of the brain starts firing off, and a whole cascade of effects happen,” explains Spencer. The brain starts to consume oxygen, bringing new blood in response to neural activity -- and that's what fNIRS detects.

Spencer’s study was the first to look at visual working memory in children. A group of 47 3- and 4-year-old kids wore soft ski hats in which fiber optic wires had been woven while they played a computer game. They were then shown shapes on the screen, and they had to tell whether the shapes that were the same or different from ones that had been shown to them a few seconds before.

The results, which were published last June in the journal Neuroimage, showed that the location of visual working memory in the kids was the same as it was in adults: "they engage part of the frontal cortex that adults use for working memory, so there's a lot of continuity in how system operates," says Spencer. 4-year olds had developed even more activity than the younger kids.

But then there was a surprise: even though kids engage the same parts of the brain, the way those brain areas work is different.

Plateau or no plateau?

Here’s an example: if you try to remember a phone number, you may be able to remember 7 digits, but trying to load a 10-digit number doesn’t work in your brain. Adults can hold on to 3-4 items in their visual working memory, and when they’re asked to hold on to more than that, their brain capacity plateaus. “This is something we can see on a neural level – if you ask an adult to hold on to more than 4 items, the brain just gives up trying and plateaus.”

But kids didn’t show that response. Kids can remember about 1.5 object features, and when they tried to remember 2 and more features, their brain signal continued to increase with no plateau. Their brains were still trying to figure out the new information.

Here’s what Spencer thinks is happening: “In order to plateau, you have to have a fairly non-distractable brain, which only holds onto what it needs. For young kids, we present one visual item, they’re fine, but at 2 they’re having a lot of trouble, at 3 items all bets are off. Their brain response is very volatile.”

Spencer says he and his colleagues were explicitly were hunting for that plateau effect, and were surprised when they didn’t find it in young kids. He says that follow-up studies are beginning to recognize the plateau effect kicking in for kids around age 7.

The ability to peer into individual brains can also help in getting kids ready for school. “Now we can measure what the brain is doing early in development, we can assess individual kids,” says Spencer. That could lead to early intervention for kids with attention problems before they start school.

Kids will be diagnosed with attention problems at the ages of 5 and up, when problems often manifest themselves in schools. “But by the time a kid is 5, they have a lot of bad habits that are hard to break,” says Spencer. “If you have good diagnostic tools for younger kids, you could get them on-target earlier and interventions could be more effective and efficient.”