One of the main claims of this blog is that a science of consciousness can’t exist without a proper philosophy of consciousness. That may seem a forgone point, but I stumble several times on researchers and authors who undervalue the contribution of philosophy on consciousness topics. I will present here an example that shows how the simplest set of data can’t be effectively understood without a solid theoretical background.

Sperling’s paradigm is a way to investigate human memory span developed by psychologist George Sperling in 1960. It made possible to discover a short-term and high-capacity memory, afterwards named iconic memory. The most famous experiment according to the paradigm consists in flashing a 3×4 matrix of different letters in front of healthy subjects, and then test their ability to recollect them. Sperling found out that even if individuals only remember a couple of items, the whole content shown remains briefly in a temporary storage only accessible via external inputs. Indeed, when the first letter in a row was suggested to them, subjects suddenly were reminded of all of the following ones. Iconic memory turns out to be a sort of buffer where perceptual information waits for becoming salient or decaying.

The point is that, although the existence of iconic memory is nowadays fully accepted, some doubts about the consciousness level of storage content still remain. Particularly two recent papers written by historically rival philosophers shows an antagonistic interpretation of Sperling’s data. On one side we have Ned Block and his “Perceptual consciousness overflows cognitive access“, on the other one there is Daniel Dennett with “Consciousness cannot be separated from function“. Both papers were published on Trends in Cognitive Sciences 15, a number that discusses the relationship between subjectivity and awareness. In this respect Block thinks that Sperling’s results prove that individuals were conscious in every moment of the whole shown matrix, although they haven’t always access to it. In Block’s mind there is a fundamental separation between what an individual feel and what he think about, and therefore Sperling’s experiments underline this separation, showing that only a little portion of the visual experience can be reported. On the other hand Dennett claims that Sperling’s subjects became conscious of the letters that they are not able to recollect only after receiving the suggestions, whereas before they are completely unaware of them. According to this point of view people are having conscious experiences only when they can use their content for tasks and communications, and they accept to have them. We can call Block’s hypothesis “the overflow argument”, and Dennett’s one “the cognitive argument”.

How should we manage a theoretical scenario where the same data are interpreted so differently? Dennettenian and Blockian positions exemplify a dichotomy that I will often stress.

Ned Block view follow common sense intuitions in defining consciousness as a product of perception mechanisms that represent information is a special way, creating a subjective feel. A consequence of this idea is that almost every viewed stimuli must have a subjective dimension, even if the subject didn’t acknowledge it – in this case Block say that there is phenomenology without access. On his side there is the everyday sensation that most of perceptual inputs are effectively felt, even if they are not clearly focused but rather faint and blurry. These ineffable feels are called “gists”, and widely discussed by literature of Blockian descent – mainly dissociationist (Koch and Tzuchiya, 2007; Laureys and Tononi, 2009).

Conversely Daniel Dennett’s cognitive approach identify consciousness utilizing behavioral markers, as the ability of recollect and verbalize perceptual content, and use it for explicit decision making or manipulation tasks. The cognitive view identifies access with consciousness, so that there can’t be consciousness without access and vice versa. Is possible, following this way, to establish a precise set of behavioral data that signals presence or absence of consciousness, a threshold based on observation of appearance of awareness in experimental subjects. Certainty an awareness measurement is complex to accomplish but at least it is based on empiric data and not on folk psychology (Dehaene, 2014; O’Regan, 2011)

Now, the controversy between Blockian and Dennettenian interpretations of Sperling’s data is an exquisitely philosophical one, and not in a derogatory sense. The veracity of the cognitive and the overflow argument depend on the definition of consciousness, and not in formal way. Define consciousness is a way of conceive it. And the distance between Block’s and Dennett’s conception can’t be bridged by experimental data. Both of them will always claim that evidence support their vision. Then we need to use philosophical tools to solve the conflict, rather than scientific ones. This does not mean that empiric research must be banned in philosophical debate – the adherence of a theory to evidence and the elegance of explanation are relevant factors. But there are other important variables, as logic and coherence. Especially relevant is verifiabiliy of hypotesis, the main reason of my bond to cognitive views: as a matter of fact the overflow argument treats an infalsifiable set of perceptions as a component of a rich subjective world that can’t be neither proven, neither denied, since it can’t manifest itself. At last a theory of consciousness must be able to really explain the weirdness of phenomenology, without fall in infinite regress traps or homuncularism. “Really explain” is not an emphasis phrase, rather a way to point out the necessity to give credit to the uniqueness of subjectivity, an aspect often underestimated by functionalist views.

Concluding. In consciousness investigation there are some core premises (as definitions, ontologies and epistemic relationships) that can’t be leaved to science. The Sperling’s paradigm double interpretation shows how the simplest data about a proven phenomenon can be extremely ambiguous when the focus goes on consciousness. Without a healthy philosophical debate some problems arise: in the best scenario key questions about subjectivity will remain unanswered, in the worst one scientists will assume uncritically philosophical premises, creating a theoretical mess. And some researchers’ production suggest that the worst-case scenario is not so unlikely to happen – keep following the blog for more material on this topic.

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