the G-man wrote:
1. Walkers have a rudimentary hive mind
I am happy to be proven wrong on this point. However, several things had led me to think this was "canon" at this point (or as "canon" as anything about the walkers is at this point):
1. Both Shane and Jim had flashes of zombies as they died as if they were seeing things through the eyes of other walkers.
2. The way that a walker will react to something almost wordlessly and the zombies nearby will seem to pick up on it.