A man comes toward you on a narrow pavement. Your 11 month old dog stops, stares, and barks at him, then looks back at you. This never happened at 7 months old.
This is frightening to be on the end of, and it is common at this age. Take it seriously, and do not conclude yet that you have an aggressive dog.
Why it starts now
New wariness of ordinary things, including unfamiliar people, is common in the second half of the first year. Owners and trainers commonly describe it as a second fear period.
Around the onset of adolescence, dogs also respond less to the cues of the person who raised them. That responsiveness returns later in the stage. Your voice competes badly with a stranger 15 feet away.
Barking works, too. The person always walks past and away, every single time, which makes barking one of the best-paid behaviours your dog has.
Tell wariness from frustration
These look similar from the other end of the lead and they need different handling.
Wariness: weight back or braced, a stiffer body, a deeper bark, ears back, and barking that carries on after the person has passed.
Frustration: a loose wriggling body, a high bark, straining forward, and a dog who is delighted on arrival. That is the dragging-to-greet problem instead.
Either way, stop letting people reach your dog while you work this out. A greeting your dog cannot manage sets the whole thing back.
Distance first, this week
Working below the threshold at which your dog reacts is the condition that lets learning happen near a trigger. That distance is almost always further than it feels.
Walk at quiet hours and on wide routes for the next 2 weeks. Fewer reactions this week is the goal, not more practice.
Cross the road, curve away, or step behind a parked car before the person is close. Turning early is not avoidance, it is the plan.
Stand 30 feet back from a path with people on it. Feed 1 treat down by your leg each time somebody passes, whether your dog looked or not.
The test is whether your dog can eat and then look back at you. If food gets refused, you are too close. Add 10 feet.
Halve the distance only after 2 easy sessions, and keep each one to 5 minutes.
What to stop today
Stop correcting the barking. Punishment-based approaches are associated with fear, avoidance and defensive aggression. A review of aversive methods found them associated with worse welfare outcomes and no training advantage.
Stop letting anyone approach to prove they are friendly. A frightened dog held still while a stranger reaches in is how a bark becomes a bite.
Stop apologising your way through it. Say please give us some space, and move. You are allowed to do that.
Stop tightening the lead as someone approaches. Keep it short but slack, and turn your body away rather than holding your dog facing the thing.
Safety note
Get help now if your dog has made contact with a person or used teeth. The same applies if they lunge hard enough that you cannot hold them. The same applies if they bark at every person, including visitors at home, or seem frightened of most things rather than a few. Book a veterinary examination as well. Sudden behaviour change warrants one, and pain frequently presents as a change in behaviour rather than as obvious lameness. This is reactivity territory, and it needs a veterinarian and a qualified behaviour professional who works with reward-based methods. Keep your dog away from people while you wait for that appointment.
When it is more than a phase
Some adolescent wariness eases over weeks with distance and food. Some of it is the start of ongoing reactivity to people, and that is a diagnosis for a professional rather than an article.
You do not have to decide which one you have. Bring in help early either way, because the handling is the same and the early weeks are the cheap ones.
What to expect
Owners usually describe weeks rather than months, with progress that moves around from day to day. Do not judge it on one bad Tuesday, and do not judge it on a narrow pavement.
Nobody can promise you the dog who walked past everybody at 7 months old. Reward-based methods and honest distances are what gets closest, and behaviour change is built from management plus reinforcement together.
Today's version, in one line: 30 feet back from a quiet path, 1 treat at your leg per person, 5 minutes, no greetings.