It is a traditional hope of comparative psychology that animal minds might be unitary, parsimonious, associative. In contrast, cognitive researchers acknowledge multiple learning systems, including humans’ capacity for explicit hypothesis testing and rule learning. The authors describe new paradigms that may dissociate the explicit from the associative and demonstrate animals’ explicit capabilities. These paradigms include matched tasks that foster explicit or associative category learning, and paradigms that disable crucial components of associative learning. Given this disabling, animals may adopt instead an alternative, more explicit learning system. The authors review this area, including research on humans, monkeys, rats, and pigeons. They also consider the evolutionary and fitness factors that might favor the development of complementary associative and explicit learning systems.