We’ve talked about encoding, storage, and retrieval, the first three steps of declarative memory. The last step is forgetting. Forgetting plays a vital role in our ability to function for a deceptively simple reason. Forgetting allows us to prioritize. Anything irrelevant to our survival will take up wasteful cognitive space if we assign it the same priority as events critical to our survival. So we don’t. At least, most of us don’t.
Solomon Shereshevskii, a Russian journalist born in 1886, seemed to have a virtually unlimited memory. Scientists would give him a list of things to memorize, usually combinations of numbers and letters, and then test his recall. Shereshevskii needed only three or four seconds to “visualize” (his words) each item. Then he could repeat the lists back perfectly, forward or backward—even lists with more than 70 elements. In one experiment, developmental psychologist Alexander Luria exposed Shereshevskii to a complex formula of 30 letters and numbers. After a single recall test, which Shereshevskii accomplished flawlessly, the researcher put the list in a safe-deposit box and waited 15 years. Luria then took out the list, found Shereshevskii, and asked him to repeat the formula. Without hesitation, he reproduced the list on the spot, again without error.
Shereshevskii’s memory of everything he encountered was so clear, so detailed, so unending, he lost the ability to organize it into meaningful patterns. Like living in a permanent snowstorm, he saw much of his life as blinding flakes of unrelated sensory information. He couldn’t see the “big picture,” meaning he couldn’t focus on the ways two things might be related, look for commonalities, and discover larger patterns. Poems, carrying their typical heavy load of metaphor and simile, were incomprehensible to him. Shereshevskii couldn’t forget, and it affected the way he functioned.
We have many types of forgetting, categories cleverly enumerated by researcher Dan Schacter in his book The Seven Sins of Memory. Tip-of-the-tongue lapses, absentmindedness, blocking habits, misattribution, biases, suggestibility—the list doesn’t sound good. But they all have one thing in common. They allow us to drop pieces of information in favor of others. In so doing, forgetting helped us to conquer the Earth.
John Medina. Brain Rules: 12 Principles for Surviving and Thriving at Work, Home, and School (pp. 155). 2014. Pear Press