The criteria Hume lists in his examination of the validity of human testimony are roughly upheld in modern social psychology, under the rubric of the communication-persuasion paradigm. Supporting literature includes: the work of social impact theory, which discusses persuasion in part through the number of persons engaging in influence; as well as studies made on the relative influence of communicator credibility in different kinds of persuasion; and examinations of the trustworthiness of the speaker.
The "custom" view of learning can in many ways be likened to associationist psychology. This point of view has been subject to severe criticism in the research of the 20th century. Still, testing on the subject has been somewhat divided. Testing on certain animals like cats have concluded that they do not possess any faculty which allow their minds to grasp an insight into cause and effect. However, it has been shown that some animals, like chimpanzees, were able to generate creative plans of action to achieve their goals, and thus would seem to have a causal insight which transcends mere custom.