  We study the breaking of gauge symmetry for higher spin theory on AdS_4 dual
to the 3d critical O(N) vector model. It was argued that the breaking is due to
the change of boundary condition for a scalar field through a loop effect and
the Goldstone modes are bound states of a scalar field and higher spin field.
The masses of higher spin fields were obtained from the anomalous dimensions of
dual currents at the leading order in 1/N, and we reproduce them from the O(N)
vector model in the conformal perturbation theory. The anomalous dimensions can
be computed from the bulk theory using Witten diagrams, and we show that the
bulk computation reduces to the boundary one in the conformal perturbation
theory. With this fact our computation provides an additional support for the
bulk interpretation.
