Wilfred Bion's observations about the role of group processes in group dynamics are set out in "Experiences in Groups and other papers," written in the 1940s but compiled and published in 1961, where he refers to recurrent emotional states of groups as 'basic assumptions'. Bion argues that in every group, two groups are actually present: the work group, and the basic assumption group. The work group is that aspect of group functioning which has to do with the primary task of the group—what the group has formed to accomplish; will 'keep the group anchored to a sophisticated and rational level of behaviour'. The basic assumption group describes the tacit underlying assumptions on which the behaviour of the group is based. Bion specifically identified three basic assumptions: dependency, fight-flight, and pairing. When a group adopts any one of these basic assumptions, it interferes with the task the group is attempting to accomplish. Bion believed that interpretation by the therapist of this aspect of group dynamics would, whilst being resisted, also result in potential insight regarding effective, co-operative group work.