Is it possible to make unconscious inferences? The limits of the influence of unconsciously perceived stimuli on conscious decisions.

According to numerous experimental and medical reports, stimuli that are not consciously perceived can exert an influence on behaviour. One of the open questions in the field of consciousness research is to what extent unconscious perception can impact our reactions. The purpose of our study was to address this issue and investigate the limits of unconscious perception. To achieve this, we designed an experiment in which participants were making various decisions based on information that was presented unconsciously with the use of the sandwich-masking technique. The experiment contained three conditions in which the same stimulus presentation parameters were used, but which differed in the complexity of the decisions (simple condition: decisions without a context; medium condition: decisions with a context; and complex condition: decisions with a context and inference). Essentially, the study compared the impact of unconscious perception across varying levels of difficulty while keeping the methodology and stimuli presentation settings constant.The results showed that decision accuracy decreased with increasing complexity—being highest in the simple condition (58%, significantly above the 50% chance level according to the Bayesian analysis), lower in the medium condition (54%, significantly above chance level), and at chance level in the complex condition. These results suggest that logical inference may establish a limit to using information perceived unconsciously. Our findings indicate that one of the functional roles of consciousness is to enable the use of information in reasoning and may provide support for certain theoretical approaches to consciousness, such as the Global Neuronal Workspace Theory.