Both a small (S) and a large (L) stimulus occurred individually and randomly over trials. The task was to make the same speeded response to either stimulus. LSSS sequences on trials N-3, N-2, N-1, and N, respectively, resulted in a faster RT to S on trial N than to S on trial N-2. However, SLLL sequences did not produce a corresponding increase in detection. Also, overall, S was less detectable than L. Suppose that the physical S on trial N was lower in detectability-memorability than a memorial S produced by S on the immediately preceding trials N-1 and N-2. If so, the physical S may have assimilated in detectability-memorability to the memorial S. explaining why its detectability increased. In contrast, the physical L may have been sufficiently high in detectability-memorability to preclude a comparable assimilation. The theory: assimilation underlies detectability, regardless of whether two components are both physical (previous research), or whether one is physical and the other is memorial (the present research).