[header] How to know if your old dog stops recognizing people [title] Pay attention to whether your dog follows people. [step] Dogs are generally capable of recognizing the faces of their owners and others they love. If your dog recognizes someone, it's likely to follow that person around, especially when greeting a person. 
If someone, say, enters a room that a dog knows, they'll generally follow them initially. [substeps] If a friend walks in that your dog knows, it's normal for your dog to follow them for a few minutes.