Between 1906 and 1909, the Austrian-born German anthropologist Richard Thurnwald undertook an expedition to Germany's Pacific colonies on behalf of the Berlin Museum for Ethnology. There he carried out a series of experimental psychological tests to investigate the mentalities and intelligence of Melanesian subjects. Due to the limitations on verbal communication, Thurnwald privileged non-verbal experiments, especially involving drawings made by his local assistants and guides. His 1913 publication Ethnopsychological Studies on South Seas Peoples reproduces some 200 of those images, which have seldom been studied since. This article examines Thurnwald's experiments in ethnopsychology through the lens of these visual materials and situates his project within larger international trends of scientific colonialism. Despite purporting to further native welfare, his application of experimental psychology to the colonial field was meant to provide solutions to the administration's most urgent problems: pacification, labour recruitment, and a declining birth rate. Yet, as this article argues, the images he collected can also be read against the grain as documents of indigenous response to German colonial rule.