Some of the polarization mechanisms that affect the dielectric and electrostrictive responses of low dielectric permittivity glasses are examined in this work. Electrostriction is the basic electromechanical coupling mechanism in all insulators. It is defined as x(ij) = Q(ijk1)P(k)P(l), where x(ij) is the strain tensor, Q(ijk1) the electrostriction tensor, and P-k the induced polarization. The electrostriction constant Q(11) (in Voigt notation) for glasses containing sodium was found to decrease with frequency in the range 0.1-10 kHz. Q(11) decreased with frequency from 0.95 to 0.55 m(4)/C-2 for sodium trisilicate glass and from 0.6 to 0.45 m(4)/C-2 for sodium aluminosilicate glass. In contrast, the Q(11) for two samples of silica glass remained nearly constant at similar to 0.4 m(4)/C-2 in this frequency range. The role played by the Na+ ion and that of silicate coordination shells in effecting the different electrostrictive responses of these glasses was analyzed.