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7

Memory

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Memory is learning we save over time. Imagine being unable to form new conscious memories. This was life for Henry Molaison, or H. M. (as psychologists knew him until his 2008 death). In 1953, surgeons removed much of H. M.’s hippocampus in order to stop severe seizures. He remained intelligent and did daily crossword puzzles. Yet from that point on he lived an unusual inner life. “I’ve known H. M. since 1962,” reported one neuroscientist, “and he still doesn’t know who I am” (Corkin, 2005, 2013). For about 20 seconds during a conversation he could keep something in mind. When distracted, he would lose what was just said or what had just occurred. Thus, he never could name the current president of the United States (Ogden, 2012).

My [DM’s] own father suffered a similar problem after a small stroke at age 92. His upbeat personality was unchanged. He enjoyed poring over family photo albums and telling stories about his pre-stroke life. But he could not tell me what day of the week it was, or what he’d had for dinner. Told repeatedly of his brother-in-law’s recent death, he was surprised and saddened each time he heard the news.

Some disorders slowly strip away memory. Alzheimer’s disease affects millions of people, usually later in life. What begins as difficulty remembering new information progresses into an inability to do everyday tasks. Family members and close friends become strangers. Complex speech becomes simple sentences. The brain’s memory centers, once strong, become weak and wither away (Desikan et al., 2009). Over a period typically lasting several years, people become unknowing and unknowable. Such is the tragedy of lost memory.

At the other extreme are people who would be gold medal winners in a memory Olympics. Russian journalist Solomon Shereshevskii, or S, had merely to listen while other reporters scribbled notes (Luria, 1968). The average person could parrot back a string of 7 or so numbers. If numbers were read about 3 seconds apart in an otherwise silent room, S could repeat up to 70. Moreover, he could recall them (and words, too) backward as easily as forward. His accuracy was perfect, even when recalling a list 15 years later. “Yes, yes,” he might recall. “This was a series you gave me once when we were in your apartment. . . . You were sitting at the table and I in the rocking chair. . . . You were wearing a gray suit. . . .”

Amazing? Yes, but consider your own impressive memory. You remember countless faces, places, and happenings; tastes, smells, and textures; voices, sounds, and songs. In one study, students listened to snippets—a mere four-tenths of a second—from popular songs. How often did they recognize the artist and song? More than 25 percent of the time (Krumhansl, 2010). We often recognize songs as quickly as we recognize a familiar voice. So, too, with faces and places. In another experiment, people were exposed to 2800 images for only 3 seconds each. Later, viewing these and other images in a second round, they spotted the repeats with 82 percent accuracy (Konkle et al., 2010). Some super-recognizers display an extraordinary ability to recognize faces. Eighteen months after viewing a video of an armed robbery, one such police officer spotted and arrested the robber walking on a busy street (Davis et al., 2013).

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How do we accomplish such memory feats? How can we remember things we have not thought about for years, yet forget the name of someone we met a minute ago? How are our memories stored in our brain? Why, when we ask you later in this chapter, will you be likely to have trouble recalling this sentence: “The angry rioter threw the rock at the window”? In this chapter, we’ll consider these fascinating questions and more, including some tips on how we can improve our own memories.