We carry out an accurate ab initio study of the interaction between ammonia and the whole series of noble gas atoms and relate the results to those of high-resolution scattering experiments that provide access to the average radial dependence of the interaction potential. The charge-displacement calculations show that charge transfer is a non-negligible, strongly anisotropies component of the interaction, governing some basic features of the potential energy surfaces especially for the heavier systems. A comparison is made with the analogous binary complexes of H(2)O with the water-H(2) system (Belpassi, L.; et al. J. Am. Chem. Soc. 2010, 132, 13046), supporting the conclusion that charge transfer plays a peculiarly special role in water's intermolecular interactions.