Short term memory capacity

The capacity of our short term memory is really limited: we can remember 3-7 items on average and the duration is approximately 30 seconds! Just imagine that you are telling something important to someone and ask him/her to remember your words... If it is not important for that person, the other will hardly remember it for a long time - unless you have a good structure and trying to chunk your topic.

Here is a short video made by the Brain Games crew at National Geographic Channel that explains how short term memory works: