
If they can crawl they will probably follow you – wherever you go.
You are the center of their world, and when you leave they feel 'separation anxiety'. They cannot know where you are and do not understand that you will come back.
If this does not happen, the child may lose interest in people and in playing, or may just play the same thing over and over again. If the main caregiver (eg. parent) leaves or is away for a long time, it is important that other special adults spend as much time as possible caring for the child. It also helps if the usual routine can be followed.