Short-term Memory

Short-term memory, is memory in our brain that will only last within a limited time. After this duration, the memory(information) will just disappear without any specific repetition. In my daily life, the most thing I can relate to this short-term memory is that when I remember a phone number, I can remember this clearly if I keep repeating the words and once I stopped repeating or after I dial the number, I cannot remember this number anymore. When I need to remember this phone number, my short-term memory is working and this can also be explained that short-term memory can be called as working memory. I believe that the duration of short-term memory is no longer than 10-15 seconds because when I am doing the experiment below, I cannot remember the words after 10 seconds and in the last trial of the experiment, I barely can remember letters more than the letters in the first several trials because of the time I need to read the letters in the last trial takes me more time(longer than 15 seconds). () However, I sometimes get confused with the paradox of memory. If we are particularly good at remembering one thing, does this mean that our short-term memory's duration would be extended to more than 15 seconds?

I found a video that is discussing about a man's amnesia. This man has a serious problem in remember things and the only thing he remember is his wife, even when his wife is talking to him, he forget the conversation immediately. His short-term memory has been damaged therefore when his wife is asking his questions about a party his wife is attending, he cannot think of the reason. When his short-term memory is damaged or no longer working good, he has amnesia. In order to explain short-term memory's duration has only about 10-15 seconds, psychologists have to duplicate the experiment to prove this research finding.