  Studies of glassy systems have shown how cyclic driving forms memories of
amplitude. We explore how choice of driving protocol reveals dramatically
different features of this memory. We model rearranging soft spots in sheared
amorphous solids as hysterons. Cyclic shear with positive and negative shear
strain reveals a return-point memory of multiple strains known from experiments
and molecular dynamics simulations, while asymmetric driving (e.g. only
positive shear strains) suppresses multiple memories. However, when we
introduce frustrated interactions between hysterons, we identify a different
mechanism that restores multiple memories for asymmetric driving and can be
used for design. Our work suggests that this enhanced memory is a signature of
frustration.
