We experience life in real-time. When we flip on the TV and survey the democratic presidential contenders, we immediately recognize the bed-raggled hair and Brooklyn accent of Bernie Sanders. The whole process — from fixing our sights on Sanders to identifying the Bern — seems to happen fluidly. Philosophers and cognitive scientists, however, say otherwise. We almost certainly don't absorb and make sense of the outside world in such a seamless manner. Yet, while some theories of consciousness depict perception as a series of isolated snapshots, a new theory presents perception as neither continuous nor discrete. Instead, it's both.
In general, two contrasting conceptual frameworks have dominated discussions of the process by which we sense and perceive our environments. Continuous theories portray consciousness as an ongoing stream — like a mental Twitter feed that needs no refreshing. A variety of research challenges continuity of perception. For example, neurogimaging studies show that people perceive stimuli occurring in rapid succession as occurring simultaneously.
Additionally, consider language comprehension. In the paper, study authors offer this example: Correctly interpreting "mouse" in the following two sentences requires hearing the last word of each: "The mouse was broken" vs. "The mouse was dead." '"We do not consciously retroactively edit our interpretation of the word 'mouse,'" wrote study authors, "but consciousness is delayed until the meaning of the sentence has been established."
Discrete theories, on the other hand, describe visual perception as occurring at isolated moments in time. But, this "snapshot" model, study authors write, is too simple and doesn't account for the fact that visual processing is much faster than conscious perception. To reconcile continuous and discrete theories, researchers from Switzerland and Germany offer an alternative "two-model" approach. In a paper published last week in the journal PLOS Biology, they break perception into two stages: unconscious and conscious.
During the unconscious stage, the brain absorbs sights, sounds, sentences, etc. in a fast, quasi-continuous manner. The brain analyzes, for example, a subway performer soliciting donations and notes properties of the questionably talented song-and-dance man — e.g., the color of his tips jar and duration of his rehearsed shtick. Then, after the stray pieces of information are collected, they're simultaneously integrated into one, coherent picture. So, after some delay, a fully rendered sight registers in the conscious mind, which is oblivious to the process underlying the first stage. Unconcious perception isn't an equal-opportunities process. Most of the information collected about the surrounding subway environment will get filtered out before reaching the conscious mind.
Combine the two stages, and a pattern emerges: brief "slices" of conscious awareness separated by 400-milisecond periods of unconsciousness. Physiologically speaking, 400 ms is a considerable stretch — "Boyhood"-long. In trying on this time-slice theory for fit, it's critical to understand the two stages as independent. "Investigating [the first]," study authors write, "does not allow us to draw conclusions regarding the latter."