Is your normally stable puppy suddenly freaking out at every little thing?
You've probably hit a normal adolescent fear imprint period.

"Animals learn the hard way which sights, sounds, and smells are relevant to survival. New research in flies shows that the timing of these cues plays an important role in how mental associations arise, and elucidates brain pathways involved in this process."

"This study reveals, for the first time, an interspecific synchronization in long-term stress levels. Previously, acute stress, has been shown to be highly contagious both among humans and between individuals of other species. Here, long-term stress synchronization in dogs and their owners was investigated..."