This paper (citation below) starts with the assumption (call the modal view) that, It is not surprising then that the modal view holds that the semantic processing of multiple-word expressions and performing of abstract mathematical computations require consciousness (reason: they are human skills). In more general terms, sequential rule-following manipulations of abstract symbols are thought to lie outside the capabilities of the human unconscious. The authors intend to weaken this modal view.
They point out that previous experiments have shown unconscious processing of: single words and numbers, simple arithmetic facts, and additions with no numbers over 6. But more demanding tasks have not been shown to be unconsciously possible. The paper attempts to show more demanding unconscious cognition. we argue that people can semantically process multiple-word expressions and that they can perform effortful arithmetic computations outside of conscious awareness.
What is different in their experiments is that unconscious processing is given some time.
In all of our experiments, we use Continuous Flash Suppression (CFS), a cutting edge masking technique that allows subliminal presentations that last seconds. CFS is a game changer in the study of the unconscious, because unlike all previous methods, it gives unconscious processes ample time to engage with and operate on subliminal stimuli. Indeed, in the present set of experiments, we show that humans can semantically process subliminal multiple-word expressions and that they can nonconsciously solve effortful arithmetic equations.
CFS consists of a presentation of a target stimulus to one eye and a simultaneous presentation of rapidly changing masks to the other eye. The rapidly changing masks dominate awareness until the target breaks into consciousness. Importantly, this suppression may last seconds. We used this technique in two different ways. In the first section, the critical dependent variable was the time that it took the stimuli to break suppression and pop into consciousness (popping time). In the second section, we used masked expressions as primes and measured their influence on consequent judgments. Objective and subjective measures ensured unawareness of the primes.
The results were that semantically incoherent expressions popped before coherent ones showing that unconscious processing was needed to explain the indication of incoherence in multiple-word expressions. And more negative expressions popped faster than non-negative ones indicating unconscious processing to find the tone of the expression. When unconsciously primed with three term arithmetic equations involving subtraction, numbers that were the answer to the equation popped earlier than other numbers, implying that the equation was solved unconsciously. Under slightly different conditions all addition equations also appeared to be solved unconsciously. These data show that unconscious processes can perform sequential rule-following manipulations of abstract symbolsan ability that, to date, was thought to belong to the realm of conscious processing.
To conclude, research conducted in recent decades has taught us that many of the high-level functions that were traditionally associated with consciousness can occur nonconsciously … for example, learning, forming intuitions that determine our decisions, executive functions, and goal pursuit. Here, we showed that uniquely human cultural products, such as semantically processing a number of words and solving arithmetic equations, do not require consciousness. These results suggest that the modal view of consciousness and the unconscious, a view that ties together (our unique) consciousness with (humanly unique) capacities, should be significantly updated.
I have a problem with both the modal view and the conclusions of this research group. There is an assumption that consciousness is a cognitive process rather than just a memory and awareness process. Once this assumption is made, it is reasonable to come to their conclusions. What I believe may be happening is that the difference is not in the number of steps or complexity of the cognition but in whether working memory and/or global access is required but the nature of the complexity. If the actual cognition was a conscious function then we really should be aware of that cognition. We should be able to experience the nitty gritty of the process. Instead we get the sub-results of cognition as each step is solved because that sub-result is needed to be in working memory. Learning, practice, habit etc. can change the size/complexity of the steps so that more can be done without recourse to working memory.
As far as consciousness being uniquely human this notion is dead but has not quite been been put in its grave yet.
Sklar, A., Levy, N., Goldstein, A., Mandel, R., Maril, A., & Hassin, R. (2012). Reading and doing arithmetic nonconsciously Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1211645109