Charness & Rabin construct a general model scoping what most precedent authors did (Fehr and Schmidt, Boltonn and Ockenfels with inequality aversion), Rabin (reciprocity), etc. However, Cox et. al. found that reciprocity is not as important as Charness & Rabin previously said and adopt a CES modified model with different results (more "cynical" but powerful I'd say).