Comparison of the velocity difference distributions |Δ ν| for neighbour galaxies with respect to the central CIG galaxy (411 fields): for the neighbour galaxies violating Eq. (1) (i.e., a factor 4 in apparent diameter with respect to their associated CIG galaxy); for the remaining neighbours (outside the factor 4 in apparent diameter); and for the whole sample of neighbours (sum of the previous two samples). The vertical line corresponds to the selected value of reference at |Δ ν| = 500 km s^-1.