The contribution of higher harmonics to the instability of a Stokes wave is characterized by considering representations of the wave envelope using both the cubic and quintic nonlinear Schrödinger equations. The authors previously addressed the role of higher harmonics by modeling the motion of the wave using Laplace’s equation, where it was found that unbounded growth of a particular harmonic implied unbounded growth of all lower order harmonics, and the Benjamin-Feir instability was recovered in the case  In the current work, a different representation is obtained, where the contribution of a particular harmonic to instability is expressed in terms of amplitudes of all harmonics, as well as the relative effect of nonlinearity and dispersion in the Schrödinger equation. While the relationship between the contributions of different harmonics is less transparent in the current treatment, it is shown that the Benjamin-Feir instability is indeed recovered for the case of the first harmonic.