The role of psychology in information science is restricted to user education/training on the one hand and system ergonomics on the other. Psychology cannot explain how to formulate a search strategy, which is a question of logic, knowledge of subject area and of terminology. Many ‘user studies’ do not compare users' actual behaviour against a normative model, and thereby psychologize the area. The concept of information input overload is introduced. Its definition, causes, effects and treatment are discussed. In particular, the contribution of the American psychologist Karl E. Weick is treated. Although he too must be criticized for psychologizing the topic, his proposal of 11 factors causing overload is a good starting point for further research on this topic. An alternative classification of factors affecting overload is introduced.