Strange Behaviour GSD

we have a GSD 10 month old bitch, she is fine & playful with other dogs and their owners.
But when people are without a dog ie. joggers, walkers & cyclists she turns into a different dog and starts to bark & growl at them, she hasn't bit anybody yet but we are a fraid that she might.
with other dog owners she lets them stroke her and give her treats.
its almost like she is telling us that people should have a dog.
we was wondering if any one else has had this problem with their GSD and what you did to combat this problem, or is it just her age?

how long have u had her and how did you socialise her?
has she been to training club and what equipment do you walk her with?

We have had her since 6 weeks old,she is walked on a choker,but then released over the park.She hasnt had must socialisation with humans only the ones she sees over the park every day.We know this is part of the problem but cannot understand why shes fine with other dog owners only.

as you say, the lack of socialisation is the problem. also, probably is the choker.
here is my bet....you feel relaxed with your girl around dogs...(all that socialisation in the park), so instinctively you are relaxed when you see them with their walkers...this reflects in how hard or relaxed you hold/walk your dog on the choker....im guessing relaxed.
However, as you have social concerns about her human unsociability and *potential* aggression, instinctively you are tense when you see people only, and this reflects in you tightening/tensing/shortening the choker.
you dont actually have to be pulling and tugging for the dog to feel the tenseness, you only have to hold the lead in a slightly less relaxed...bending your elbow and kinking the lead, for example.

(however, does she also lunge, and if so, do you react with pull and tug?).

its called defensive handling...you send your stress messages thru the lead to the dog, the dog reacts according to the message you give...being a GSD, you have the added breed trait (plus socialisation prob).
therefore, dog makes neg assoc between people and tight lead and takes your cue to see off the 'problem'.

We have been walking her on the lead through the main part of the park where there are alot of people and sometimes shes fine with them as long as i keep telling her shes a good girl then give her a treat when shes gone through the crowds
But what about when shes off the lead and sees alone person?
When she is occupied with toys or sticks in the park nobody seems to bother her.
Why is she friendly towards other dog owners ?

ok. so it is sometimes on lead and always off-lead behaviour?
when she passes thru the initial crowd, what do you mean she is 'sometimes fine'.
are you tensing the lead as described in my last post?
aside from the choker, how long is your actual lead?
and then what does she do when she is off the lead, and what are the people doing before she does it?

did she go to training class when younger?

i have some further ideas dependant upon your replies, but they are still based upon my premise earlier.

Sometimes when she walks thru a crowd on the lead and im talking to her she ignores everyone then i treat her. i do tense the lead so she doesnt pull towards someone.the lead and choker are quite short so she walks quite close to me.
When she is off the lead and sees someone just walking on there own she will run up towards them and start barking ,obvoiusly this scares alot of people and if they shout at her it makes her worse.Its just people without dogs of there own she barks at

thats kinda what i was figuring.
so she walks thru the crowd on a short tensed lead and choker. but you dont treat her until the end.
my guess is you havent tried treating her whils walking thru the crowd, as you are focussed on getting thu safely and quickly. most likely, she wouldnt take a treat then, as she would pick up on your stress, and dogs dont eat when stressed (like humans really).
then she has a moment of stress relief getting to the end so is just about relaxed enough to take a treat.
also, im guessing whilst walking thru that crowd and you are saying your "good girls" you may be saying it in a reassuring tone?
this is counter-productive as this reinforces a dogs fears and worries. that would add to a message of stress and worry given thru a short lead.

so, now she is at the end. my reckoning is she has now built a stress peak....GSD's are prone to nerves anyway....so she aint really relaxed when you then let her off...she will be on edge and over-aroused..
remember, also, she has already been taught that people without dogs are to be seen off as you have made the negative association thru the defensive handling when on the lead.
so she is this state and is left out there in the scary zone to take care of the situation herself, as has been taught...'see off the problem'
these people probably only have to glance her way. Of course, the shouting just re-confirms everything.

I have some solutions, but i really gotta be put the door so will be back in about 1 hour.

so should i try treating her when walking thru a crowd of people ? What about holding the lead tighter because if she wants to bark at someone she will pull towards them and i will want to restrain her because of the people becoming freightnened.Or are you saying relax the lead,i just dont want her jumping at people.

Why isnt she bothered with the owners who have dogs