Chicken is a game modeled by two players' in game theory. The main principle of the game is that while each player prefers not to yield to the other, the worst possible outcome occurs when both players do not yield. A form of Chicken is seen in Gattaca.
Chicken is seen in the early portion of the movie, when Vincent and Anton are younger. The point of the game is to swim out as far as they can in the ocean, and whoever turned back first lost. Vincent, with genetic mutations and many problems, was often surpassed by Anton, his younger brother. However, Vincent had challenged Anton one day, and he surprisingly won, and saved the latter from drowning.
Chicken is last seen later in the movie, when the two brothers are older; Vincent, with a borrowed ladder, is currently working in Gattaca, under the name of "Jerome Morrow" while Anton is a police investigator. Vincent once again challenges his younger brother to one last game of chicken, and the two are off once again. Like before, Anton is fearful that they will get lost and almost drowns. Luckily for him, Vincent turns around and saves him once again.