Common principles underlie representation of order in short-term memory and order judgment.

Although many studies have explored magnitude effects in numerical cognition, the representation of order information has received only limited interest. We explored the hypothesis that common abstract ordinal representations underlie the representation of order information across different domains. We tested this hypothesis by determining the similarity of distance effects in short-term memory (STM) order probe recognition (did ‘8’ occur before ‘5’ in the list ‘3, 6, 5, 4, 8, 7’ presented a few seconds ago?) and in order judgment tasks (does ‘1’ occur before ‘2’), both numerical and alphabetical stimuli were used. In numerical cognition, adjacent numbers are typically judged more slowly than more distant numbers. In fifty healthy adults, we observed significant distance effects across all tasks: in the order judgment tasks, adjacent numbers/letters were judged more slowly than more distant numbers/letters; in the STM tasks, order recognition was slowed for stimuli stemming from adjacent positions in the STM list as compared to stimuli stemming from more distant positions. Regression slopes for distance effects were identical across the different tasks and conditions. Furthermore, the size of distance effects correlated significantly across tasks, except for the order judgment task with numerical stimuli. We will discuss the implications of these results for a hypothetical common representational system of order information in STM and numerical cognition.