The absence of the dip in backward π+ photoproduction is examined with both the "Nγ–Nα exchange degeneracy coupled with duality" and the "I = 3/2 dominance" points of view. A uniform combination of beta functions is employed using no arbitrary satellite terms but including parity doublets of the Nα, Nγ, and Δδ trajectories.
The Breaking of Exchange Degeneracy and the Hadronic Selection Rules