The size of the emission volume of pions and kaons, r ππ and r KK , were measured in the hadronic Z 0 decays through the two-pion and two-kaon Bose-Einstein correlations near threshold. Recently the emitter size of the two identical baryons, ΛΛ(ΛΛ), was evaluated from the dependence of the fraction of the spin S=1 state on the energy near threshold where it is affected by the Pauli exclusion principle. Here we show that the r dependence on the particle masses, namely the hierarchy r ππ > r KK > r ΛΛ observed in the Z 0 hadronic decays, is well described in terms of the Heisenberg uncertainty principle. A good description can also be obtained via the virial theorem when applied to a general QCD potential. Other available approaches are also discussed.