Can't Get 2D Sprite to Animate

So I have an animation for my 2D sprite titled "WalkingDown". It's attached to the player controlled sprite and the script i'm using is below. For some reason it keeps telling me that "down" isn't defined in the input but it is defined by default in unity under the vertical tab in edit -> projects Settings -> Input

 #pragma strict
 
     // Variables
     var WalkingDown : Animation;
 
 function Start () {
 
     if (Input.GetButtonDown ("down")){
     
         animation.Play("WalkingDown");
     
     }
     
     else {}
 
 }
 
 function Update () {
 
 }