Over the past two decades, researchers have explored the question of whether animals have access to their knowledge states, and further, whether they moderate their behavior in relation to this knowledge. This paper summarizes the research that has been done using the so-called ‘information-seeking paradigm’, pioneered by Call and Carpenter in 2001. The paper describes patterns of findings that have emerged across the primate order, alternative interpretations of these findings, and remaining questions. It closes with suggestions for further investigation in the field, with a focus on exploring the following: What types of information do animals gather? Where do they access information? And, do animals modify their search behavior depending on how informative the source is?