Thus, we design a bimodal mixture model in which we assume that each pair of eventualities (e o , e r ) belongs to a latent class z, and each class is associated with two distinct multinomial distributions from which the two eventualities are independently drawn.
the probability of generating a particular pair is: Each class can be thought of as a general type of reciprocity, such as an action followed by appreciation, or an attack followed by retaliation.