Information Processing, Human Error and the Learning Process — Page 160, Lesson 248

I want to walk you through the limitations of short-term memory and the methods we can use to improve it, and then we'll move into long-term memory. Let's start with the capacity limit. Your short-term memory can only hold a maximum of about 7 ± 2 unrelated items — that's between five and nine pieces of information. Once you exceed that limit, one or more of those items are likely to be lost, or they get transposed — meaning you mix up the order. This is critically important when you're designing checklists or deciding what to put into a radio telephony message. If you've ever received a complicated departure clearance, you know that much of that information simply cannot be memorised; you have to write it down. Short-term memory is also highly sensitive to interruption. Here's a real-world example: if a controller passes a frequency to a pilot, and very soon after reception an interruption takes place, the pilot can retain it instantly at that moment, but it is immediately lost. The pilot then has to request that the information be re-transmitted. So interruptions are dangerous for short-term memory. Now, there are three main tools to increase short-term memory. The first is chunking. We can expand the number of items retained by grouping related material together. Chunking works best when you are already familiar with the information — that's your mental model. For example, a long telephone number like 012357176204 contains ten or more digits, but if you chunk it as 0123 5717 6204, you now only have three items to hold. The French telephone directory prints numbers in separated blocks, making good use of this tool. When a Frenchman gives you a telephone number, he will sometimes pass it in chunks, each chunk consisting of three figures. The second tool is association. This technique is used by many when remembering spoken lists of items. You imagine a wild and bizarre association and attach it to each item on the list. Many politicians use this method when putting faces to names. The third tool is mnemonics. This is the art of making up a word, phrase, or sentence in order to remember many points. It's very useful. Let me give you typical examples of items stored in short-term memory during flight: radio frequencies, heights and pressure settings prior to selection, short ATC instructions, and verbal responses to checklists prior to execution. Now let's move to long-term memory. If the information in short-term memory is rehearsed, it will be transferred into long-term memory. It is believed that information is stored in long-term memory for an unlimited time period, although frequently there are retrieval problems. One major disadvantage is the time it takes to access that information. Long-term memory contains information that can be classified into three types: - Semantic memory — this is your general knowledge, facts, and concepts. - Episodic memory — this is memory of personal experiences and specific events. - Procedural memory — also called motor programmes. This is memory for how to do things, like the sequence of actions in a procedure. So to summarise: short-term memory is limited to about 7 ± 2 items and is easily interrupted, but we can improve it with chunking, association, and mnemonics. Rehearsal moves information into long-term memory, which has unlimited storage but takes time to access, and it's divided into semantic, episodic, and procedural memory.