The interference mechanism of the spatial–numerical association of response codes effect in mixed contexts containing numbers and letters

We designed two experiments to investigate the interference mechanism of the spatial–numerical association of response codes (SNARC) effect in randomly presented mixed contexts of numbers and letters, after manipulating the binding pattern of numbers and letters with left or right response position in situations where the ratio of numbers to letters was 1:3. The results from Experiment 1 showed that the SNARC effect occurred both for numbers and letters when binding small numbers with letters A–C, or large numbers and letters E–G. In Experiment 2 the SNARC effect was absent in classification of both numbers and letters when binding the digits 1–3 with letters E-G and binding 4–7 with A–C. This suggests that interference between the spatial representation of letters and numbers in working memory can lead to the disappearance of the SNARC effect in mixed contexts.