The spatial coding mechanism of ordinal symbols: a study based on the ordinal position effect

The ordinal position effect refers to a phenomenon in which items positioned early in an ordinal sequence receive a faster response with the left key than with the right key, and the opposite response pattern occurs when items are positioned later in an ordinal sequence. Previous studies have suggested that ordinal symbols are spatially represented from left to right, thus leading to the ordinal position effect; however, the spatial coding mechanism of ordinal symbols remains unclear. Therefore, the present study explored the ordinal position effect as an index to judge the spatial coding of ordinal symbols, and three experiments were performed to investigate the spatial coding mechanism of ordinal symbols. In particular, a novel transitory ordinal sequence was induced by presenting successive dots of different colors centrally (Experiment 1), from left to right or from right to left (Experiments 2 and 3), and participants were asked to memorize the successive dots in the correct order. Then, the participants were asked to press a key to provide a response corresponding to a probe dot's ordinal position (Experiments 1 and 2) or its spatial location (Experiment 3). The following results were identified: (1) The ordinal position effect occurred when responses were based on the ordinal position regardless of the presentation direction, and (2) the ordinal position effect was overridden when responses were based on the spatial locations of the ordinal symbols. From these results, we concluded that the spatial coding of ordinal symbols is flexible and that ordinal symbols are encoded depending on the specific experimental context.