A direct replication: Unconscious arithmetic processing

Across two experiments involving four presentation times in total, Sklar et al. (Proceedings of the National Academy of Sciences of the United States of America, 109, 2012, 19614) found that complex subtraction equations can be solved without awareness of the equations. These findings challenge the current position that consciousness is necessary for performing abstract, rule-following tasks. Given the important implications of their work, we aimed to directly replicate Sklar's findings using a larger sample (n = 94) from a different population. Using continuous flash suppression, we investigated if people were able to solve an equation after subliminal (1,300 ms) exposure to it. We found evidence of unconscious subtraction consistent with Sklar et al., albeit the effect is weak. Critical review of our results and implications for further research are discussed.