1. A method of processing a video image of a human subject to determine an open vs. closed eye state of the subject, the method comprising the steps of: (a) forming a set of training examples based on training images of human subjects, each training example including training input data characterizing a respective training image and a desired eye state classification for that training image; (b) performing a genetic programming (GP) process in which a prescribed number of GP classification programs are formed and evolved over a prescribed number of generations, and the classification error of each GP classification program is evaluated with respect to the training examples; (c) selecting and saving the GP classification program whose classification error is smallest; (d) repeating steps (b) and (c) to form a set of saved GP classification programs; (e) characterizing said video image of said subject to form non-training input data; (f) applying the non-training input data to each of the saved GP classification programs to form classification outputs; and (g) combining said classification outputs to determine an open vs. closed eye state of said subject.