We consider primordial perturbations from general two-field inflation in interaction picture. We verify that normalized to the single-field case, the power spectrum of scalar perturbations in the two-field version is identical beyond any slow roll approximation, except with different scalar spectral index. We then report that the two bispectrums also coincide at the leading order of slow roll parameters, which divide only at the next-leading order. Combing the scalar spectral index and the tensor-to-scalar ratio, we finally show that two-field chaotic and natural inflation can be distinguished by current BK14/Planck and future CMB-S4 experiment respectively.
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