anchor.diff:  
   (defun test-tree ()
     (random-expand (random-expand (random-expand (random-expand (random-expand (random-expand (get-root))))))))
  +
  +
  +;;(defparameter *game-channels* '("x" "y" "z" "width" "height" "avg-y" "stdv-y" "min-y" "max-y" "avg-u" "stdv-u" "min-u" "max-u" "avg-v" "stdv-v" "min-v" "max-v"))
  +
  +;;****************************************************************
  +
  +;; In order to run some games just replace the parameters below
  +;; and run the method exec-game. The common parameters to play with
  +;; are the ones found at the bottom.
  +
  +;; Definition of game parameters
  +(defparameter *current-game* 0)
  +(defparameter *spy-loops* '())
  +(defparameter *scalable-features* '("x" "y" "z" "width" "height"))
  +(defparameter *moving-avg-span* 4)
  +(defparameter *success-log* (make-array *total-number-of-games*))
  +(defparameter *moving-avg-increase-rate* 0.1)
  +(defparameter *verbose-level* 1)
  +;; Common parameters
  +(defparameter *number-of-objects-per-scene* 5)
  +(defparameter *total-number-of-games* 500)
  +(defparameter *saliency-threshold* 0.01)
  +(defparameter *pruning-threshold* 0.9)
  +(defparameter *pruning-min-age* 20)
  +(defparameter *scaling* t)
  +(defparameter *game-channels* '("x" "y" "width" "height" "avg-y" "avg-u" "avg-v"))
  +
  +
  +(exec-game)
  
positive.code:   "pruning for the feature-detectors (channels) of the agent"
    (loop for fd in feature-detectors do
         (tree-pruning (sensory-channel-discrimination-tree fd)))
    feature-detectors)
  
  ;; Function to run a single discrimination game
  (defun run-single-game(agent &optional print)
  
negative.code:   "Gets the age of a node"
    (- *current-game* (node-birth-game node)))
  
  ;; Executes a prunning in a tree
  ;; Function doesn't work properly
  (defun tree-pruning(tree)
    "Pruning depending on the age and score of the nodes"
    (let ((score (node-score tree)) (age (node-age tree)))
      (if(and (> age *pruning-min-age*) (< (/ score age) *pruning-threshold*))
         (progn 
          ;;(format t "EXECUTING PRUNING")
           (setf (tree-node-left-child tree) nil)
           (setf (tree-node-right-child tree) nil))
         (when (and 
  