Within the field of knowledge representation, the problem of how to represent conjunctions. In visual perception, in order to pick out a blue square from a display including a collection of red squares and blue triangles, it is not enough to isolate its non-unique shape or its non-unique colour; it is necessary to bind each shape to its colour and then to isolate the unique conjunction (blue + square). In language comprehension, in order to understand a sentence such as The cause of Mary's hatred of John, in Peter's opinion, was John's betrayal of her trust, it is necessary to bind the noun phrase John's betrayal of her trust to The cause of Mary's hatred of John. The problem of binding underlies symbolic representation in general. See also feature integration theory, government and binding.