A wide variety of species, including human beings, exhibits a remarkably reliable behavior pattern, known as spontaneous alternation behavior (SAB), that has intrigued researchers for over seven decades. Though the details may vary depending on species and setting, SAB essentially entails first choosing one member of a pair of alternatives and then the other, without instructions or incen tives to do so. Spontaneous alternation is manifested even in the early trials of a discrimination-learning experiment, where only one of the choices is reinforced. Indeed, that was the setting in which SAB...