This past weekend, my wife went on a retreat while I stayed home with our 1-year-old twins. Since they were sleeping when she left, there was no separation anxiety. The next morning, I changed them as usual, but instead of taking them to our bedroom where my wife normally feeds them, I took them downstairs for milk in their highchairs. After that a brief moment of agitation, they went through the rest of the day without seeming to notice my wife was missing. In fact, they didn't much notice anything different unless there was some change to their schedule; who was taking care of them didn't seem to have any noticeable impact on their behavior or attitude.
When my wife returned home, they obviously recognized that she was gone. When we take them to nursery at church, they notice when we leave. But as far as I can tell, they don't miss us when we are gone. It got me thinking: when do children first become aware of the absence of someone important to them? Are there any studies on when children might start missing a parent who is no longer around?