[SPOILERS]Milton's theory on the Walkers remembering their past selves may be true? Or am I over thinking this?

In the most recent episode we watched Milton conduct an experiment on an older, dying man. Milton wanted to know if once you were a walker, if you remembered details of your previous life (Family, friends etc.). His experiment did in fact fail but, remember from season 1 Morgan (the first guy Rick met out of the hospital)? His zombie-fied wife returned over and over to where she died, and attempted to get back into the house. Is Milton's theory correct? Or am I just over thinking things?