The Superhuman Mind

Cases of extraordinary mental ability

Kids as Super-Witnesses

Storing raw and uninterpreted data in memory may carry testimonial advantages

The U.S. legal system gives preference to adult testimony in court cases. In 2002 Thomas Junta was accused of killing a man in a Massachusetts hockey rink quarrell in 2000. Thomas’ son 12-year-old Quinlan Junta was a key defense witness for his father but his testimony did not convince the jury. Thomas was found guilty and sentenced to 6 to 10 years in state prison.

The case is a good illustration of the weight the U.S. legal system gives to child versus adult testimony. Children’s testimony often is not taken seriously. Cornell professors Valerie Reyna and Chuck Brainerd believe this is a mistake. In their studies of memory in children, they have found that children's short-term memory can be more accurate than that of adults. The reason for this is not that children have better functional memory capacities than adults but that their short-term memory system works according to a different set of principles that allow for more accurate recall, the scientists say.

“Short-term memory” refers to one of two abilities: the ability to hold information in your head for up to a few minutes, or the ability to remember detailed facts, events or scenes for minutes, hours or days. The former type of short-term memory is also sometimes called "working memory" or "functional short-term memory." The two kinds of memory engage different brain regions, reports a research team in the November 9, 2009 issue of PNAS. Working memory engages prefrontal brain areas, whereas storage-based short-term memory involves the hippocampus, an area of the brain in the temporal lobe that is also crucially involved in some forms of long-term memory.

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While working memory in the prefrontal areas of the brain and the hippocampus are crucial for most forms of memory storage and memory retrieval, working memory and the hippocampus are not the place where information is stored, according to the newest models of memory. According to an older model of memory, the hippocampus was a place for storing sensory information until it eventually would be relocated to outer lawyers of the cerebral cortex. Recent data collected by neuroscientists Howard EichenbaumJohn Serences and colleagues and Jesse Rissman and Anthony D. Wagner, however, indicate that this model of sensory memory is mistaken. On a more plausible model, which we might call “the reactivation model of memory,” memory storage consists in a strengthening of the perceptual and cognitive pathways that originally processed the information. The hippocampus does not store information for later retrieval. Instead it functions as a control center in the strengthening process. Over time the hippocampus no longer is needed to maintain the neural networks. Working memory in the prefrontal cortex plays a similar role as a control center for very short-term memory. This brain structure doesn’t store any of the information that it can recall if needed.

Children store information differently from adults. In adult information can be stored for a lifetime. But this is not so in young children, report psychology professors Wolfgang Schneider and Michael Pressley in their book Memory Development between Two and Twenty. They attribute the transient nature of young children's memories to a lack of the ability to categorize and interpret. An ability to interpret the meaning of an event or scene helps to retain memories for the long term. Since young children are unable to fully interpret their sense impressions, their memories will tend to be short-lived. Their memories never become stored in a form that will allow the memories to last very long.

The way memories are stored might explain the transient nature of children’s memories. When a memory is stored, the brain deposits proteins at the neurons’ synapses, the place where neurons communicate with each other. This form of strengthening of certain pathways makes it possible to use attention and other top-down processes to recall what happened. However, the hippocampus is for the most part needed to keep track of the relative order of events and for filling in gaps in memories through repeated rehearsal, perhaps during dreaming. In children, working memory plays a greater role than the hippocampus in determining what can and cannot be recalled. Like hippocampus, working memory keeps track of the order of events but it does not fill in gaps in memories, and it cannot keep track of information for a very long time.

While children do not have the same long-term or interpretive memory capacities as adults, their shortterm memory can be better, report Ohio State researchers in the August, 2004 issue of Psychological Science. Whereas adults process sensory input for short-term storage by sorting it into abstract categories, children process stimuli on the basis of observations of noticeable features. In their book The Science of False Memory from 2005, Reyna and Brainerd argue for a similar conclusion. Adults who are asked to recall memories fill in the details, as their brains automatically are interpreting what is actually recalled before the information can be reported. As children record what actually happened and are less likely to interpret what happened, they are also less likely to produce false memories, the researchers say.

Neurologically, this makes a lot of sense. The younger a child is, the more she relies on working memory rather than the hippocampus for memory retrieval. But we know that information that is retrieved through working memory without having undergone rehearsal in hippocampus is more akin to the information that originally entered the system. So, reports of this information are inevitably going to be more accurate that reports that rest on millions of rehearsal processed by the hippocampus.

Berit Brogaard is a Professor of Philosophy with joint appointments in Philosophy, Psychology and the Center for Neurodynamics at the University of Missouri-St. Louis. She directs the St. Louis Synesthesia Lab. more...

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