Memory is based on connections: everything from emotions to images, touch even smell.
But those connections are only as good as they are used.
So if you are distracted when your brain tries to make those connections, haven’t used that memory in a while or there is some other factor (e.g. you went to the bar and had a little too much) – the connection is broken.
But not completely.
The “tip of the tongue ” is when there is enough of the connection so that you “know” there is a memory but the specifics are missing.
Latest Answers