The Brain: Forgetting So We Remember, Avoiding Overload

Nov. 29, 2012 — -- We accumulate so many memories that it's a wonder our brains don't clog, strangling us on the trivia of our daily lives. How do we recall the memories that are important to us without flooding our brains with the details of every insignificant event? How do we separate the memories we need from the mountains of garbage?

According to ongoing research, we separate the wheat from the chaff by shutting down some memories, at least temporarily, to allow that one chosen treasure to resurface. In short, we forget, so we can remember.

New research into "retrieval-induced forgetting," an awkward phrase that is easily forgotten, is reshaping much of what we have known about how memories are organized and retrieved. Psychologists Benjamin C. Storm of the University of California, Santa Cruz, and Robert A. Bjork of UC Berkeley, along with other cognitive scientists around the world, have produced some potentially game-changing results.

In laymen's language, the research suggests the healthy human brain comes equipped with something like a super-smart Web browser. A cue that should trigger the retrieval of a specific memory also allows the browser temporarily to suppress many memories that are similar to the target, but not precise enough.

The beauty of such a system, if it continues to be validated by other research, is that it would allow us to recall positive memories, which we prefer over negative memories, so every cue doesn't dredge up sad or heartbreaking remembrances. Yet even the saddest memories remain buried in our brains, and the temporary suppression that keeps them from constantly resurfacing doesn't bury them forever. They are suppressed, but not totally forgotten.

The research is based chiefly on word association. A cue of automobile-red, for example, may remind someone of their father's red Oldsmobile, but not necessarily of the tragic accident that killed him.

Storm and a colleague, Tara A. Jobe of the University of Illinois at Chicago, conducted a series of experiments, and report the results in the current issue of the journal Psychological Science. The first experiment allowed them to determine how efficient each participant was at suppressing -- or forgetting, as they prefer to call it -- some memories to facilitate recalling a specific memory. Surprisingly, the participants were unable to recall word associations they had practiced as well as words they had not practiced, indicating some inhibiting mechanism was at work.

That experiment allowed them to evaluate each participant's level of "retrieval-induced forgetting." Those who scored well had an especially effective "browser," while others were only mediocre, and some were even weaker.

The participants were then instructed to recall an autobiographical memory -- something that they experienced personally.

"There is a positivity bias in autobiographical memory such that people are more likely to remember positive events from their past than they are to remember negative ones," the scientists said, and much other research supports that.

The memories recalled by the participants suggest a very significant role for "retrieval-induced forgetting."

"Participants who exhibited lower levels of retrieval-induced forgetting (weak browser) recalled significantly more negative memories" than participants with a strong browser, the study concluded.

The scientists also recruited participants who were depressed, at least to some degree, and that group recalled far more negative memories, especially among those with a weak browser. That suggests a relationship between depression and recall, although this work does not determine if the negative memories resulted from depression, or if depression partly stemmed from the flood of sad memories.

A good browser might help keep negative memories, and possibly depression, at bay.

"Without such a mechanism, people might find themselves increasingly inundated by disruptive, and often painful, autobiographical memories," Storm and Jobe conclude.

In an earlier study, Storm described the power of memories this way:

"These things could completely overrun our life and make it impossible to learn and retrieve new things if they were left alone, and could just overpower the rest of memory."

By the way, we may prefer happy memories to sad recollections, but that doesn't mean sad memories are weaker. Psychologist Elizabeth Kensinger of Boston College found that we may not like sad memories, but we retain them in vivid detail.

Kensinger, who uses brain scans to study her subjects, said in releasing her study that someone who has been confronted by an assailant with a gun is likely to remember exactly what the gun looked like, even though other details may be hazy. She thinks that's probably because no one wants to be in that situation twice, so remembering the gun is likely to keep us on alert in the future.

"These benefits make sense within an evolutionary framework," she wrote.

However, it's probably not a good thing to be constantly haunted by a man with a gun. That's why, according to a growing number of researchers, our brains need good browsers. They help us keep sad, and even just the mundane, memories on the back burner.