Dogs learn how to interpret the world around them between the ages of 8 and 16 weeks. This is when they learn that other dogs can be friends and new people aren’t dangerous. Some react fearfully, others turn their fear into aggression. Signs of a poorly socialized dog are behaviors usually associated with “bad” dogs, but unsocialized dogs aren’t bad, they’re reacting to the world around them in the only way they’ve learned how. Fearful behavior when around strangers and/or other dogs, behaviors might include flattened ears, lip licking, yawning, cowering, avoiding eye contact, and tail tucked between the legs. Aggressive behavior when around strangers and/or other dogs, behaviors might include intent staring, holding ears erect, excessive barking, snarling, growling, and snapping. Dog backs up or raises his hackles when another person or dog approaches. Fearful or aggressive behavior when on walks, even if no other people or dogs are around, overexcitement around other people and dogs.