Whether the GR asymptotic symmetry group should be larger or smaller than the original BMS group is a subject of research, since various and differing extensions have been proposed in the literature. Most notable is the so-called extended BMS group where the six-dimensional Lorentz group is also extended into an infinite-dimensional group of so-called superrotations. Just like displacement memory effect is associated with a BMS supertranslation, a new gravitational memory effect, named spin memory effect, can be associated with a superrotation of the extended BMS group. But unlike displacement memory, which can represent a shift to a supertranslated time frame, spin memory does not correspond to a spacetime merely superrotated from an early frame.