1. A system for training a trainee to recognize facial expressions from animations of computer-simulated faces, the system comprising: a trainee interface configured to display a facial animation; a machine-readable repository of facial expression overlays each corresponding to an emotion; an expression injection module configured to combine one of the expression overlays into a facial animation to form a combined animation, by mapping at least a portion of the expression overlay to at least a portion of the facial animation, the expression injection module configured to provide the combined animation for display in the trainee interface; a trainee evaluation module configured to receive from the trainee a response to the combined animation displayed in the trainee interface; and a computer system operative to execute at least one of the trainee interface, the expression injection module, and the trainee evaluation module, the computer system also operative to access the repository.