Order is ordinal in serial memory

Four experiments investigated the importance of metric relationships in the representation of order in memory. We used a cued recognition procedure in which a cued letter in a probe array is matched to a memory list. The spacing between the letters in the memory list and the probe array was either the same or different. Theories of serial memory in which order is based on the ordinal relationships predict that cued recognition performance would remain the same over changes in spacing. Theories of serial memory in which order is based on metric relationships predict that performance would decline when spacing changed. In all four experiments, we found memory performance was the same regardless of the spacing of the arrays. We compared memory performance to perceptual matching performance, displaying the probe and the "memory list" simultaneously. Perceptual comparisons were strongly influenced by changing the spacing. Performance was worse when the spacing differed. We conclude that order in perception is based on metric relationships but order in memory is not. These results support ordinal theories of serial memory. Even if metric relationships are stored in memory, they do not appear to be necessary for item selection and retrieval. (PsycInfo Database Record (c) 2026 APA, all rights reserved).