A central question within the realm of memory research is whether retaining information over short periods of time versus longer periods of time (whether minutes or weeks) is different. In 1890, William James distinguished “primary memory,” composed of past experiences that are active within consciousness, from “secondary memory,” composed of experiences that are not stored at the conscious level but can be recalled. James believed there to be limits to how much information is available in primary memory. Research has generally demonstrated that 7 ± 2 items can be stored at once in a person’s mind, but also that “recoding” items using past knowledge (for example, breaking longer strings into smaller recognizable pieces) can increase memory capacity.