How much socialization did you do with him? When he was a baby, did you take him all sorts of different places? Did you enroll him (with you) in classes as a young puppy?
Did you meet his parents before you got him? Did you see where he was raised and did you talk to the breeder? Do you know if he or she began socialization before he left his littermates?
Sabra - female GSD - born April 30, 2012
Sargeant - rescued senior GSD male/foster failure - approximately ten years old (August 2013)
Max - rescued GSD - Dec 22, 2010 to March 7, 2012 - at the bridge
Sable - rescued GSD - at the bridge