Robinson Splitting Theorem and ${\mathrm{\Sigma }}_1$ Induction

The Robinson Splitting Theorem states that a c.e. degree $\mathbf{b}$ splits over any low c.e. degree $\mathbf{c}<\mathbf{b}$. We prove that a weaker version of this theorem holds in models of ${\mathrm{P}}^{-}+\mathrm{I}{\mathrm{\Sigma }}_1$, with lowness replaced by superlowness.