I've been banging my head on this one for the last two days. For some reason backbone is sharing parent instance data across inherited child models. Heres an example: 

```
var Base = Backbone.Model.extend({

  index : []

});

var Group = Base.extend({

  initialize : function() {
    this.index.push('from group');
  }

});

var User = Base.extend({

  initialize : function() {
    this.index.push('from user');
  }

});

var user = new User();
console.log(user.index); // ['from user']

var group = new Group();
console.log(group.index) // ['from user', 'from group']

```

---

What I'm looking for is:

```
console.log(user.index); // ['from user']
console.log(group.index) // ['from group']

```

Any insights?

Thanks!
Matt