Reviews and Papers by Howard Gutowitz
The above described ant (and some variations) was originally studied by Chris Langton (then at the Santa Fe Institute, more recently a co-founder of the Swarm Corporation). Later, Jim Propp generalized the ant by considering each cell to be in one of n different states: each ant has some "internal programming" which tells it whether to turn left or right when the cell is in that state. This "program" can be represented as a string of n Ls and Rs, and the kth letter represents the ant's action when it comes to a cell in state k. For example, Langton's ant, described above, is a 2 state ant with the rule string LR (or in binary 10, so we call this "ant number 2"). The 7 state ant with rule string LLRRRLR (ant number 98) turns left when it visits a cell in state 1, 2, or 6, and right when it visits cells in state 3, 4, 5, or 7.
For all such generalized ants, one can readily see that if there is at least one L and at least one R in the rule string, the track of the ant will always be unbounded. And certain ants exhibit recurrent symmetry, while others have apparently chaotic behavior. "