

As our final exercise, we will watch an example of cumulative selection
vs. single step selection in behavioral evolution.

Imagine two rats that have to learn to negotiate a maze to get
a food reward at the end.  Rat 1 learns only via single step selection--he
does not learn from previous experience, but wanders randomly around
the maze.  On the other hand, rat 2 remembers previous mistakes (via
a neural process of cumulative selection) and retains previous correct moves.

We can think of the series of moves that are required to negotiate the
maze as the "target" string of letters, where each letter
has the following meaning:  

      U = move up 
      D = move down
      L = move left
      R = move right

(Press the "Pg Dn" (page down) key to continue... ) 



Thus, if our target string of letters (the solution to the maze) is

        ULRD

then the rat must make the following moves in the correct order:
up, left, right, and down. 

The process of getting this string of "solution" letters correct is 
very similar to getting the string of letters "methinks it is like a weasel"
correct (as in our previous examples).   We would expect that a process
of cumulative selection will find the correct solution string much
faster than the process of single step selection.


Let's watch and see how quickly each rat gets to the end of the maze.

Press ESC to begin.
