Abstract: This disclosure relates to methods and apparatus for generating criteria for information retrieval tasks. A quantifying unit is trained through machine learning to assign relevance values to functional brain imaging potentials measured from a person. This quantifying unit is then used when the person performs an information retrieval task by reading a primary document. The quantifying unit assigns relevance values to text items viewed by the person in the primary document. Based on these relevance values a criterion is generated for the information retrieval task, and potentially relevant secondary documents are retrieved from a document database based on whether or not, or to what extent, they meet this criterion.