Our memories depend on our ability to recall details about the world—a child’s face, a goose, a lake. To transform them into actual experiences, though, the brain must somehow merge these individual elements into an integrated whole—the look on that child’s face when she sees a flock of geese suddenly take flight from a lakeside stand of reeds.
A cohesive sense of memory relies on other factors, too. Our survival over the millennia has depended on recalling not only the right information—say, a lion or a snake—but also the context. Did we encounter the animal during a surprise confrontation on an isolated stretch of African savanna or as part of an unhurried viewing at the San Diego Zoo?