Coexistence and interplay of multiple memories in a sheared suspension

We conduct experiments using a rheometer on memories in a soft material that stays far from equilibrium: a non-Brownian, neutrally buoyant suspension. The system learns the strain amplitude of oscillatory shear, forming a specific memory that can be recalled, and this in effect tunes the future mechanical response at that strain. We focus on the system's capacity to retain multiple memories, formed by varying the strain amplitude, and we examine the behaviors of these memories over time and the limits on their coexistence. We also consider implications for the system's ability to compare the current strain amplitude to past driving amplitudes, akin to some kinds of working memory in neuroscience.