Boxer obsessive chasing

Question
I have an 11 month old boxer bitch, she has had an obsession with chasing
leaves since we began walking her and chases anything that blows in the
wind, she is so obsessed that she shakes and pulls and pulls to get to hold of
the leaves, I have tried distracting her with toys, food etc and this works for a
little while but she always returns to her previous behavior, we have had input
from  behaviorists but to no avail nothing has really helped.  Walking her has
become a nightmare, she goes out twice a day, runs and plays with her sister
in the garden and we also do basic training and tricks with her.   Her sister
has no problems like this.  What are we doing wrong.  It isn't nice watching
her obsessing, it wears her out and she has no self control.


Answer
I suggest you consult a veterinary behaviorist.  The dog may have a low level seizure disorder.  The dog might also have a much higher prey drive than your other Boxer.  As for poor input by "behaviorists", I don't get it, this isn't all that difficult a problem!  BUT here's some advice: following full neurological evaluation by an expert veterinarian, learn about clicker training.  I suggest you begin with Karen Pryor's book (she's the ultimate authority on this training) "Getting Started: Clicker Training for Dogs" and then follow up your newly acquired knowledge with a visit to her forum's section about managing the behaviors you don't want:
http://www.clickertraining.com/node/834

A good understanding of the science and approach is required BEFORE using it on this dog for this purpose OR you might inadvertently reward the obsession (thought process).  You have to know what your dog is LEARNING, not just what you are trying to teach (as John Fisher often said).  This requires reading the dog's body language communication so that the MOMENT your redirection succeeds you can click/treat.  In other words: dog is obsessing, you redirect with conditioned word (cue, command), dog has learned that cue earns high value reward (click/juicy treat) because you've conditioned the dog in place(s) where such distractions don't occur; dog responds (body language indicates thought process is now focused on you), click/treat, move on.  As the dog is consistently rewarded for NOT obsessing, the behavior should extinguish.

Also: capturing chase behavior (prey related) can help enormously.  Teaching this dog to CHASE (balls, not too small though, dog could swallow them) on cue (command) for reward can then control the prey drive (to some extent, dependent upon how high it is).