Diagram of the 2-back WM task used to identify and characterize sensory-biased and sensory-independent WM structures. Subjects observed a stream of visual or auditory stimuli and reported 2-back repeats via button press. Sensorimotor control blocks consisted of the same stimuli, without repeats included. (A) The visual stimuli comprised black-and-white photographs of faces, drawn from a corpus of student ID photos. (B) The auditory stimuli comprised recordings of cat and dog vocalizations.