The basic tenets and ideas of Morten Overgaard's article (2001) are appreciated and elaborated on by pointing out the consequences for empirical studies designed according to Overgaard's approach. What seems amiss in many present day consciousness studies, is an elaborated use and focusing upon experiential properties, and how they can be assessed in an empirical setup. Overgaard's article is a necessary first step towards what can be viewed as a "whole" science of consciousness. The commentary finally presents one direct consequence that these thoughts might have for empirical research - the study of phantom limbs.
2. In most cases, there is no reason to doubt the truth of a person's introspective reports. Utterances like "I hear music" or "I feel something touching my arm" generally elicit no doubt as to whether we should believe the person has had this experience or not. If we, at the same time, can observe the person actually being touched on his arm at the given moment, we have further reason for believing his statement. This is so far a very straightforward matter, and social interaction would indeed be troublesome if this was not to be the case. The basis for any communicative act that intends to report conscious phenomena is also based upon this assumption, and thus what I identify as the present use of introspective reports in consciousness studies. Perceptions of stimuli on a computer screen with various durations are reported as either seen or not seen, sometimes including a post-hoc measure of subliminal effects. If we are interested in studying conscious phenomena in this way, we are about to make a category mistake. It stems from a misuse of the naive belief in a 1:1 correspondence between words and experiences, and hence what I see as the primary problem addressed in Overgaard's article.
3. In using and interpreting introspective reports, there is a significant difference between what could be called a Naive Correspondence Theory (NCT) and a Developed Correspondence Theory (DCT). Using a method based upon the NCT, subjects are generally asked to report what they experience as described above. Their reports are then used as basis of a correlation with e.g. a measure of neural activity, and furthermore as basis for hypothesis testing: Is the subject conscious of the stimulus - yes or no? Are there significant differences in neural activity between conscious and non-conscious states, as measured by e.g. EEG - yes or no, and so on. At the root of the NCT method, reports of conscious experiences are to be uttered in a predefined matter, in line with explicitly (sometimes only implicitly) defined categories. Experiences are to be reported in concordance with those categories, and additional experiences that cannot be described by strict use of these terms, are thus not seen as relevant for the present study - either by the experimenter or the subject himself. In other words, there is a possibility that when the subject is conforming to the report possibilities, he is also leaving out those experiences that cannot be reported using the prescribed categories.
4. What seems to be missing is the use of more elaborate descriptions of conscious experiences, and thus also a more critical view of the categories being used. Instead of asking the subject to answer in a dichotomic yes-no fashion, or settle with a description like "I felt a touch on my right wrist", it is my conviction that it is both possible and necessary to use an elaborated method of introspective reports. Let me give an example from the study of phantom limb phenomena, especially the work of V.S. Ramachandran and his colleagues (V.S. Ramachandran and Hirstein, 1998, V.S. Ramachandran and Ramachandran, 1999), who has found a way of inducing the phantom sensation by brushing a cotton swab on the person's chinoramputation stump. When stimulated, the patient, who is blindfolded to prevent visual feedback, readily reports sensation in the phantom limb. Using this method, Ramachandran has documented a reorganisation of the homonculus, or body representation, following amputation of a limb, and also claims to have addressed the conscious states by so-called phenomenological reports. I think there is still much to be said and done in the study of phantom limb perception. Let me show this by briefly presenting an example; the misreferral phenomenon.
5. In the misreferral of phantom limbs, brief and successive brushes with a cotton swab over the chin ipsilateral to the amputation (in arm amputees), the dominant focus is on the perception of the phantom arm or hand. What is readily left out, or put in a subordinate clause, is that the patients are also experiencing a feeling on the stimulated chin. Although this should be no surprise - amputation of a limb is not supposed to abolish the sensation of another body area - it seems we are letting something out by ignoring this specific phenomenon. If we are indeed interested in the conscious perception of the phantom limb, we should ask questions like "Is the patient experiencing the chin and hand/arm simultaneously, or is this some sort of bistable phenomenon", and "How real is the hand/arm experience compared to the intact hand/arm, and how does the chin experience compare to the experience of the "intact" chin?". It is my belief that we, by asking these questions and thoroughly addressing them in the experimental setup, are likely to end up with two results. First, we will learn more about the nature of conscious experience of phantom limbs, compared to intact limbs, and second, the findings can be used in the correlation with measures of neural events, like the EEG or functional MR, and thus illuminate the relationship between conscious phenomena and brain processes. In line with these thoughts, utterances like "I felt a touch on my wrist"should be treated otherwise than initially done, and hence the way Ramachandran et al. have done so far. They should simply not be taken at face value, but rather undergo careful scrutiny. When addressing this by asking the patient to report in terms of e.g. duration, intensity, "realness" compared to an intact limb, it is possible for us to have a better understanding of the conscious phenomena that we are studying. This is what could be referred to as a Developed Correspondence Theory.
6. Why is this discussion - and thus the present article - necessary? As Overgaard writes, the use of a specific word or phrase is referring to a certain mental state, ideally in a 1:1 fashion, although it cannot reveal or communicate the conscious content itself. Herein lies the problem in a nutshell: if we are unable to have a real 1:1 correspondence between words or phrases, how can we indeed use verbal reports as reliable data in the study of conscious phenomena? One certain failure is to use the naive approach, as described above, since it gives no possibility of detecting minor differences between phenomenal states that could otherwise be reported and described as different, and since it actually more or less ignores essential features of a given conscious experience. We are therefore in great need of a developed nomenclature and methodology in the study of conscious phenomena, and in using introspective reports. If we are to have a real science of consciousness, these questions are among the most immediate and important at present. Overgaard's article is therefore a most welcome contribution on this matter.
Overgaard, M. (2001) The Role of Phenomenological Reports in Experiments on Consciousness PSYCOLOQUY 12(029) http://www.cogsci.soton.ac.uk/cgi/psyc/newpsy?12.029
Ramachandran, V.S. & Hirstein, W., 1988. The perception of phantom limbs. The D. O. Hebb lecture. Brain, 121 (Pt 9), 1603-1630 http://brain.oupjournals.org/cgi/reprint/121/9/1603.pdf
Ramachandran, V.S. & Rogers-Ramachandran, D., 2000. Phantom limbs and neural plasticity. Archives of Neurology, 57 (3), 317-320. http://archneur.ama-assn.org/issues/v57n3/abs/nnr8257.html