Sketch of the distinction between short-term and long-term memory and relations between memory strength and duration. It is commonly assumed that short-term memory lasts seconds to a few minutes (digit span, 5 bits of information), while long-term memory may last lifelong. Evidence for the division into these two memory systems comes from experimental psychological research and from findings in amnesic patients. Word list learning (of about 10–20 words) reveals the so-called primacy and recency effects: the first and the last perceived words are remembered best and those in the middle worst. It is assumed that the words perceived first have already been transmitted for long-term storage (recency effect), while those perceived last are still in the short-term memory storage (primacy effect). Amnesic patients usually have a preserved short-term memory ability and would show a primacy, but no recency effect.