The spin structure functions g1 for the proton and the deuteron have been measured over a wide kinematic range in x and Q2 using 1.6 and 5.7 GeV longitudinally polarized electrons incident upon polarized NH3 and ND3 targets at Jefferson Lab. Scattered electrons were detected in the CEBAF Large Acceptance Spectrometer, for 0.05 \u3c Q2 \u3c 5GeV2 and W \u3c 3 GeV. The first moments of g1 for the proton and deuteron are presented – both have a negative slope at low Q2, as predicted by the extended Gerasimov–Drell–Hearn sum rule. The first extraction of the generalized forward spin polarizability of the proton γ p 0 the Q2 evolution of the first moment of g1 shows agreement in leading order with Heavy Baryon Chiral Perturbation Theory. However, a significant discrepancy is observed between the γ p 0 data and Chiral Perturbation calculations for γ p 0, even at the lowest Q2
