Although both objects and scopes look quite similar and are both collections of key/value pairs, they are very different and don't actually overlap.
To add a variable to a scope, you have two options:
1. Set a new variable to an initial value all in one line:

var aPerson = {name: "jess"};

1. Make a statement starting with var, followed by the name you want to use for your variable, but don't assign a value yet:

var aPerson;

To add a property to an object you again have 2 options:

// To an already declared variable
aPerson.age = 25;
// To a brand new object 
({name: "jess"}).age = 25; 

Fallthrough

While failed variable lookups within a context fall through to the containing context, it's not the case that failed property lookups on objects fall through to a containing object:

var aPerson = {name: "jess"};
aPerson.age = 25;
log(aPerson.age.birthday); // undefined

While we are on the subject of accessing properties, there are two different ways to do it. There is dot notation (aPerson.age) or using brackets and quotation marks (aPerson["age"]).

Besides the global context object, there isn't any way to actually reference a context (even by using the this parameter), meaning that it's impossible to do things like return a context from a function, make a variable refer to one, or get an array full of contexts. However for each variable in the global context, there is a corresponding property on the global object which can be referenced in the browser as 'window':

var globalVariable = "jess";
log(globalVariable); // jess
log (window.globalVariable); // jess
var globalScope = function () {
    return window;
};