Part of a lecture about human memory — how we take in information,

Section 4. You will hear part of a lecture about human memory — how we take in information, keep it, and bring it back. First, you have some time to look at questions 31 to 35. Now listen carefully and answer questions 31 to 35. MAN: Good afternoon. Today we're going to explore human memory, how we take information in, hold on to it, and later bring it back, and why the whole system is far stranger than it feels from the inside. The first and most important point is that memory is not a single store, but several systems working together. When information first reaches us through the senses, sight, sound, touch, it is held for only the briefest instant in what psychologists call sensory memory, a fraction of a second, just long enough for us to notice that something is there before it fades. MAN: If we pay attention to it, that information passes into short-term memory, sometimes called working memory. This store is strikingly limited in two ways. It is brief, lasting only seconds unless we act on it; and it is small, holding only a handful of items at once, the classic estimate is about seven, which is roughly why an old-style telephone number is the length it is. To keep anything for longer, it must be transferred into long-term memory, and here everything changes: long-term memory appears to have an almost unlimited capacity, and can hold information for a lifetime. MAN: How is a lasting memory actually formed? Psychologists describe three stages. The first is encoding, in which the brain converts an experience into a form it can store, and this is where attention matters most. The second is storage, holding the information over time. The third is retrieval, pulling it back out when it is needed. A failure at any one of these three stages feels to us, from the inside, simply like 'forgetting', even though the underlying causes are quite different. Before you hear the rest of the lecture, you have some time to look at questions 36 to 40. MAN: A crucial part of the process happens, surprisingly, while we are asleep. During sleep the brain replays and reorganises the day's experiences, strengthening the connections that matter and discarding the rest, a process known as consolidation. This is one very good reason why a full night's sleep before an examination is worth more than an extra hour of late-night cramming. Much of this work depends on a small, curved structure buried deep in the brain, named, from its seahorse shape, the hippocampus, which is essential for laying down new long-term memories. MAN: So how can we deliberately remember better? The oldest method is simple repetition, going over material again and again, what psychologists call rehearsal, which gradually fixes it in place. And retrieval is far easier when we are handed a cue, a hint or reminder linked to the original memory, which is exactly why walking back into a room can suddenly bring back what you had gone there to fetch. MAN: Two final warnings. First, memory is nothing like a video recording played back unchanged. Every single time we recall an event, we actively rebuild it, and small errors and later suggestions creep in, so our memories are not always accurate, however vivid and however confident we may feel about them. And second, emotion has a powerful grip on what we keep: events that stir strong emotions, whether joy or fear, are burned in far more deeply than ordinary days, which is why you may recall a dramatic moment from years ago yet forget what you had for lunch last Tuesday. That is where we'll stop. That is the end of Section 4. You now have some time to check your answers.