We propose fuzzy cognitive maps, a branch of fuzzy logic, to study interaction of factors affecting processes and details of the approach are discussed. Application of the technique to discriminate between factors affecting slurry rheology is demonstrated. It has been shown that hydrodynamic interaction, effective particle concentration, shape and size, temperature and shear rate have a significant influence on the slurry viscosity. The complex interaction of the various factors delineated by previous workers is also presented.