Alon Goldstein

The scope of unconscious processing has long been, and still remains, a hotly debated issue. This is driven in part by the current diversity of methods to manipulate and measure perceptual consciousness. Here, we provide ten recommendations and nine outstanding issues about designing experimental paradigms, analyzing data, and reporting the results of studies on unconscious processing. These were formed through dialogue among a group of researchers representing a range of theoretical backgrounds. We acknowledge that some of these recommendations naturally do not align with some existing approaches and are likely to change following theoretical and methodological development. Nevertheless, we hold that at this stage of the field they are instrumental in evoking a much-needed discussion about the norms of studying unconscious processes and helping researchers make more informed decisions when designing experiments. In the long run, we aim for this paper and future discussions around the outstanding issues to lead to a more convergent corpus of knowledge about the extent – and limits – of unconscious processing.

Unconscious processes are mental states that occur in the absence of subjective awareness. We offer a focused historical survey of the robust debate about the nature of unconscious mental processing, from ancient and medieval theories that allow for bodily functions without subjective awareness to the 20th century acceptance of autonomous unconscious processing. The background introduction culminates with the rise of cognitive science in the latter half of the 20th century, as dual systems theories claimed that the mind had two forms of processing: an unconscious system that is associative, fast, and automatic and a conscious system that performs sequential, deliberative, and slow mental functions. More recently, the “cognitive unconscious” has been discovered to perform most if not all cognitive functions including higher-level cognitive processing, such as addition and subtraction. Despite a rich history of experimental methods and findings, recent criticisms are forcing scientists to reexamine these advancements. We are optimistic that the field will develop novel techniques that answer these criticisms, including measures for studying subjective reports in the absence of subjective awareness of the content of the unconscious state and the act of reporting.

Perceptual conscious experiences result from non-conscious processes that precede them. We document a new characteristic of the cognitive system: the speed with which visual meaningful stimuli are prioritized to consciousness over competing noise in visual masking paradigms. In ten experiments (N = 399) we find that an individual's non-conscious visual prioritization speed (NVPS) is ubiquitous across a wide variety of stimuli, and generalizes across visual masks, suppression tasks, and time. We also find that variation in NVPS is unique, in that it cannot be explained by variation in general speed, perceptual decision thresholds, short-term visual memory, or three networks of attention (alerting, orienting and executive). Finally, we find that NVPS is correlated with subjective measures of sensitivity, as they are measured by the Highly Sensitive Person scale. We conclude by discussing the implications of variance in NVPS for understanding individual variance in behavior and the neural substrates of consciousness.