Kids' unreliability as witnesses: Hard-wired into the brain?

Take a look at the following maps of brain activity:

The maps were made using ERP recordings of volunteers' brains as they were tested for memory of pictures. The ERP (event-related potential) records electrical potentials using a variety of electrodes (primarily EEGs, or electroencephalograms) placed on the scalp. The white regions of the diagrams represent areas of greater brain activity. What's striking about the diagrams is that while for the most part they are similar, kids' brains show a strikingly different pattern for memory of the context of an item than adults do.

To understand what all this means, we need to back up just a bit. It has long been known that children's eyewitness testimony is significantly less reliable than adults' testimony. Is this simply because adults have better memories? Not necessarily. Children actually have more vivid memories than adults do, but these memories apply not only to things they've actually seen, but also to things that they've only been told about. Where children seem to have difficulty is in recalling whether they really saw something, or just heard about it or read it in a book. In short, they're not as good as adults in remembering the context in which they acquired a memory, even though the substance of the memory may be just as accurate.

There is a considerable amount of research suggesting that memory for items is typically stored in roughly the center of the brain (the medial temporal lobes and diencephalon), while memory for context is stored in the front of the brain (the frontal lobes). Other studies have shown that the frontal lobes develop more slowly than the rest of the brain. So if kids' frontal lobes are less fully developed than those of adults, they might very likely have more difficulty remembering context than adults.

Let's put this in the context of a court case that has received a bit of attention in the media lately: It's entirely possible that a child might have considerable difficulty remembering whether Michael Jackson really touched them "down there," or if a psychologist or lawyer merely suggested that Jackson might have done such a thing.

The chart at the beginning of this article was made by Yael Cycowicz, David Friedman, and Martin Duff, of the New York State Psychiatric Institute, who developed an experiment to test how well kids could remember the context of a set of pictures ("Pictures and Their Colors: What Do Children Remember?" Journal of Cognitive Neuroscience, 2003).

Cycowicz et al. asked groups of 10-year-olds, 13-year-olds, and adults to memorize a set of pictures, as well as the color of their frames. They were then tested on the pictures while attached to the ERP devices. The kids and teens were just as good as the adults at remembering whether they had seen a particular picture before, but adults were significantly better than kids at remembering the frame color for each picture.

Even more interesting is what's going on in the brains of each group while they take the test. Adults and children show the same pattern on the item test, where they simply had to remember whether they had seen a picture before. However, for the context test, the pattern is entirely different. About a half second after the test picture was displayed, everyone had the same ERP. After a second had passed, the picture changed dramatically. For adults, activity was concentrated in the front of the brain, but for kids, it was still primarily in the back of the brain!

Next Cycowicz and her colleagues performed one more bit of analysis. They noticed that if they removed the bottom third of the results from the 10-year-old group, the remaining kids performed as well as the adults on the context test. They then looked at the ERPs of those kids, and found they were similar to the entire group of 10-year-olds (see the diagram in the lower right corner of the chart). So even kids who were good at remembering context processed the information differently from adults.

Kids simply don't remember context as well as adults do, and even when they do remember it, they remember it differently from adults. This means their courtroom testimony must be treated with extreme care. Unfortunately for the kids, it also means that identifying predators on children becomes even more difficult than it already is.