Ab initio computations at the MP2 level on five dimers and five cyclic trimers, drawn from water, ammonia, and formaldehyde are presented. Trimers have been drawn to present cyclic X-H---Y patterns. Particular attentions have been devoted in analyzing the energetic contributions resulting from cooperative effects in the trimer binding energies (BEs) and in analyzing the trends of several parameters from monomers to dimers and from dimers to trimers [in particular, the trends of the R(X-H) bond lengths, of the R(X---Y) distances, of the delta nu(XH) shifts in the nu(XH) stretch vibrational frequencies, and of the electronic density rho(c) value at the XH---Y axis critical point when it exists]. The results have exhibited that cooperative effects represent from 10% to 16% of the trimer BEs and that they reinforce, from dimers to trimers, the trends observed for the above parameters from monomers to dimers. In particular, for "typical'' X-H---Y HB (i.e., where X and Y atoms correspond to oxygen or nitrogen atoms), R(X-H) bond lengths are increased within 0.01 Angstrom from monomers to dimers and from dimers to trimers, R(X---Y) distances shortened within 0.18 Angstrom, rho(c) values increased by about 17% and nu(XH) red-shifted from 18 to 164 cm(-1) from dimers to trimers. As contrasted to those HBs the R(X-H) and delta nu(XH) parameters corresponding to C-H---Y interaction (with Y=O or N) follows an opposite trend from monomers to dimers and from dimers to trimers (i.e., they are respectively smoothly shortened and blue-shifted). All of these results therefore exhibit the great incidence of cooperative effects on the properties of X-H---Y interactions (corresponding to typical HBs or not), which are of importance to understand the properties of biochemical systems.