Human Memory, Computer Memory

Almost all of those limits start with a peculiar fact about human memory: Although we are pretty good at storing information in our brains, we are pretty poor at retrieving it. We can recognize photos from our high school yearbooks decades later, yet find it impossible to remember what we had for breakfast yesterday. Faulty memories have been known to lead to erroneous eyewitness testimony (and false imprisonment), to marital friction (in the form of overlooked anniversaries), and even death (skydivers, for example, have been known to forget to pull their rip cords, accounting by one estimate for approximately 6 percent of diving fatalities).

Computer memory is much better than human memory because early computer scientists discovered a trick that evolution never did: organizing information by assigning every memory to a master map in which each bit of information to be stored is assigned a uniquely identifiable location in the computer’s memory vaults. Human beings, by contrast, appear to lack such master memory maps and retrieve information in far more haphazard fashion, by using clues (or cues) to what’s being looked for. In consequence, our memories cannot be searched as systematically or as reliably as that of a computer (or Internet database). Instead, human memories are deeply subject to context. Scuba divers, for example, are better at remembering the words they study underwater when they are tested underwater rather than on land, even if the words have nothing to do with the sea.

Sometimes this sensitivity to context is useful. We are better able to remember what we know about cooking when we’re in the kitchen than when we’re, say, skiing. But it also comes at a cost: When we need to remember something in a situation other than the one in which it was stored, the memory is often hard to retrieve. One of the biggest challenges in education, for example, is to get children to apply what they learn in school to real-world situations. Perhaps the most dire consequence is that human beings tend to be better at remembering evidence consistent with their beliefs than evidence that contradicts those beliefs. When two people disagree, it is often because their prior beliefs lead them to remember (or focus on) different bits of evidence. To consider something well, of course, is to evaluate both sides of an argument, but unless we also go the extra mile of deliberately forcing ourselves to consider alternatives—which doesn’t come naturally—we’re more prone to recall evidence consistent with a belief than inconsistent with it.

Overcoming this mental weakness (known as confirmation bias) is a lifelong struggle; recognizing that we all suffer from it is an important first step. We can try to work around it, compensating for our inborn tendencies toward self-serving and biased recollection by disciplining ourselves to consider not just the data that might fit with our own beliefs but also the data that might lead other people to have beliefs different from ours.

Gary Marcus describes how human memory is haphazard, context-specific. We can't retrieve a specific detail easily, but we can if we are in the right context to trigger its retrieval.