Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!rutgers!princeton!mind!harnad From: harnad@mind.UUCP Newsgroups: comp.cog-eng,comp.ai Subject: Re: Objective measurement of subjective variables Message-ID: <469@mind.UUCP> Date: Tue, 27-Jan-87 14:44:16 EST Article-I.D.: mind.469 Posted: Tue Jan 27 14:44:16 1987 Date-Received: Wed, 28-Jan-87 21:06:07 EST References: <842@mtund.UUCP> Organization: Cognitive Science, Princeton University Lines: 174 Summary: Psychophysics is the objective study of discrimination performance, not conscious experience. Xref: watmath comp.cog-eng:42 comp.ai:183 adam@mtund.UUCP (Adam V. Reed), of AT&T ISL Middletown NJ USA, wrote: > Stevan Harnad makes an unstated assumption... that subjective > variables are not amenable to objective measurement. But if by > "objective" Steve means, as I think he does, "observer-invariant", then > this assumption is demonstrably false. I do make the assumption (let me state it boldly) that subjective variables are not objectively measurable (nor are they objectively explainable) and that that's the mind/body problem. I don't know what "observer-invariant" means, but if it means the same thing as in physics -- which is that the very same physical phenomenon can occur independently of any particular observation, and can in principle be measured by any observer, then individuals' private events certainly are not such, since the only eligible observer is the subject of the experience himself (and without an observer there is no experience -- I'll return to this below). I can't observe yours and you can't observe mine. That's one of the definitive features of the subjective/objective distinction itself, and it's intimately related to the nature of experience, i.e., of subjectivity, of consciousness. > Whether or not a stimulus is experienced as belonging to some target > category is clearly a private event...[This is followed by an > interesting thought-experiment in which the signal detection parameter > d' could be calculated for himself by a subject after an appropriate > series of trials with feedback and no overt response.]... the observer > would be able to mentally compute d' without engaging in any externally > observable behavior whatever. Unfortunately, this in no way refutes the claim that subjective experience cannot be objectively measured or explained. Not only is there (1) no way of objectively testing whether the subject's covert calculations on that series of trials were correct, not only is there (2) no way of getting any data AT ALL without his overt mega-response at the end (unless, of course, the subject is the experimenter, which makes the whole exercise solipsistic), but, worst of all, (3) the very same performance data could be generated by presenting inputs to a computer's transducer, and no matter how accurately it reported its d', we presumably wouldn't want to conclude that it had experienced anything at all. So what's OBJECTIVELY different about the human case? At best, what's being objectively measured happens to correlate reliably with subjective experience (as we can each confirm in our own cases only -- privately and subjectively). What we are actually measuring objectively is merely behavior (and, if we know what to look for, also its neural substrate). By the usual objective techniques of scientific inference on these data we can then go on to formulate (again objective) hypotheses about underlying functional (causal) mechanisms. These should be testable and may even be valid (all likewise objectively). But the testability and validity of these hypotheses will always be objectively independent of any experiential correlations (i.e., the presence or absence of consciousness). To put it my standard stark way: The psychophysics of a conscious organism (or device) will always be objectively identical to that of a turing-indistinguishable unconscious organism (or device) that merely BEHAVES EXACTLY AS IF it were conscious. (It is irrelevant whether there are or could be such organisms or devices; what's at issue here is objectivity. Moreover, the "reliability" of the correlations is of course objectively untestable.) This leaves subjective experience a mere "nomological dangler" (as the old identity theorists used to call it) in a lawful psychophysical account. We each (presumably) know it's there from our respective subjective observations. But, objectively speaking, psychophysics is only the study of, say, the detecting and discriminating capacity (i.e., behavior) of our trandsucer systems, NOT the qualities of our conscious experience, no matter how tight the subjective correlation. That's no limit on psychophysics. We can do it as if it were the study of our conscious experience, and the correlations may all be real, even causal. But the mind/body problem and the problem of objective measurement and explanation remain completely untouched by our findings, both in practise and in principle. So even in psychophysics, the appropriate research strategy seems to be methodological epiphenomenalism. If you disagree, answer this: What MORE is added to our empirical mission in doing psychophysics if we insist that we are not "merely" trying to account for the underlying regularities and causal mechanisms of detection, discrimination, categorization (etc.) PERFORMANCE, but of the qualitative experience accompanying and "mediating" it? How would someone who wanted to undertake the latter rather than merely the former go about things any differently, and how would his methods and findings differ (apart from being embellished with a subjective interpretation)? Would there be any OBJECTIVE difference? I have no lack of respect for psychophysics, and what it can tell us about the functional basis of categorization. (I've just edited and contributed to a book on it.) But I have no illusions about its being in any better a position to make objective inroads on the mind/body problem than neuroscience, cognitive psychology, artificial intelligence or evolutionary biology -- and they're in no position at all. > In principle, two investigators could perform the [above] experiment > ...and obtain objective (in the sense of observer-independent) > results as to the form of the resulting lawful relationships between, > for example, d' and memory retention time, *without engaging in any > externally observable behavior until it came time to compare results*. I'd be interested in knowing how, if I were one of the experimenters and Adam Reed were the other, he could get "objective (observer-independent) results" on my experience and I on his. Of course, if we make some (question-begging) assumptions about the fact that the experience of our respective alter egos (a) exists, (b) is similar to our own, and (c) is veridically reflected by the "form" of the overt outcome of our respective covert calculations, then we'd have some agreement, but I'd hardly dare to say we had objectivity. (What, by the way, is the difference in principle between overt behavior on every trial and overt behavior after a complex-series-of-trials? Whether I'm detecting individual signals or calculating cumulating d's or even more complex psychophysical functions, I'm just an organism/device that's behaving in a certain way under certain conditions. And you're just a theorist making inferences about the regularities underlying my performance. Where does "experience" come into it, objectively speaking? -- And you're surely not suggesting that psychophyics be practiced as a solipsistic science, each experimenter serving as his own sole subject: for from solipsistic methods you can only arrive at solipsistic conclusions, trivially observer-invariant, but hardly objective.) > The following analogy (proposed, if I remember correctly, by Robert > Efron) may illuminate what is happening here. Two physicists, A and B, > live in countries with closed borders, so that they may never visit each > other's laboratories and personally observe each other's experiments. > Relative to each other's personal perception, their experiments are > as private as the conscious experiences of different observers. But, by > replicating each other's experiments in their respective laboratories, > they are capable of arriving at objective knowledge. This is also true, > I submit, of the psychological study of private, "subjective" > experience. As far as I can see, Efron's analogy casts no light at all. It merely reminds us that even normal objectivity in science (intersubjective repeatability) happens to be piggy-backing on the existence of subjective experience. We are not, after all, unconscious automata. When we perform an "observation," it is not ONLY objective, in the sense that anyone in principle can perform the same observation and arrive at the same result. There is also something it is "like" to observe something -- observations are also conscious experiences. But apart from some voodoo in certain quantum mechanical meta-theories, the subjective aspect of objective observations in physics seems to be nothing but an innocent fellow-traveller: The outcome of the Michelson-Morley Experiment would presumably be the same if it were performed by an unconscious automaton, or even if WE were unconscious automata. This is decidely NOT true of the (untouched) subjective aspect of a psychophysical experiment. Observer-independent "experience" is a contradiction in terms. (Most scientists, by the way, do not construe repeatability to require travelling directly to one another's labs; rather, it's a matter of recreating the same objective conditions. Unfortunately, this does not generalize to the replication of anyone else's private events, or even to the EXISTENCE of any private events other than one's own.) Note that I am not denying that objective knowledge can be derived from psychophysics; I'm only denying that this can amount to objective knowledge about anything MORE than psychophysical performance and its underlying causal substrate. The accompanying subjective phenomenology is simply not part of the objective story science can tell, no matter how, and how tightly, it happens to be coupled to it in reality. That's the mind/body problem, and a fundamental limit on objective inquiry. Methodological epiphenomenalism recommends we face it and live with it, since not that much is lost. The "incompleteness" of an objective account is, after all, just a subjective problem. But supposing away the incompleteness -- by wishful thinking, hopeful over-interpretation, hidden (subjective) premises or blurring of the objective/subjective distinction -- is a logical problem. -- Stevan Harnad (609) - 921 7771 {allegra, bellcore, seismo, rutgers, packard} !princeton!mind!harnad harnad%mind@princeton.csnet