Short-term memory for symmetry

Abstract Symmetric cascades of dots were generated in a continuous random sequence such that each dot had a partner reflected about a vertical or horizontal axis, respectively. Between each point and its partner a temporal delay was introduced. While the brightness of the dots appeared constant within 120–140 msec, symmetry perception ceased at delays in the range of 50–90 msec, depending on observers, type of symmetry and plotting rate. These findings in conjuction with three control studies suggest that memory span for position Information is limited to 50–90 msec while memory for brightness information lasts for 120–140 msec. Perturbation experiments (with no delay) in which a certain proportion of dots had no symmetrical partner were compared with the delay experiments for equal performance, and equivalence curves between delay and perturbation rate were obtained. While performance depended on the type of symmetry and plotting rate, the shape of equivalence curves remained unchanged.