clutch什么意思
TOIL: GROUNDING LANGUAGE IN PERCEPTUAL CATEGORIES
Angelo Cangelosi
Centre for Neural and Adaptive Systems
School of Computing
University of Plymouth
Drake Circus
Plymouth PL4 8AA (UK)
angelo@soc.plym.ac.uk
Stevan Harnad
sabCognitive Science Centre
University of Southampton
Highfield
Southampton SO17 1BJ (UK)
harnad@cogsci.soton.ac.uk
Corresponding address:
Angelo Cangelosi
School of Computing
University of Plymouth
Drake Circus
Plymouth PL4 8AA (UK)
Email: angelo@soc.plym.ac.uk
Tel. +44 1752 232559
Fax +44 1752 232540
Note: Submitted to Evolution of Communication, special issue on Grounding Language edited by L. Steels
TOIL: GROUNDING LANGUAGE IN PERCEPTUAL CATEGORIES
Abstract
Using neural nets to simulate learning and the genetic algorithm to simulate evolution in a toy world of mushrooms and mushroom-foragers, we place two ways of acquiring categories into direct competition with one another: In (1) "nsorimotor toil,” new categories are acquired through real-time, feedback-corrected, trial and error experience in sorting them. In (2) "symbolic theft,” new categories are acquired by hearsay from propositions – boolean combinations of symbols describing them. In competition, symbolic theft always beats nsorimotor toil. We hypothesize that this is the basis of the adaptive advantage of language. Entry-level categories must still be learned by toil, how
ever, to avoid an infinite regress (the “symbol grounding problem”). Changes in the internal reprentations of categories must take place during the cour of learning by toil. The changes can be analyzed in terms of the compression of within-category similarities and the expansion of between-category differences. The allow regions of similarity space to be parated, bounded and named, and then the names can be combined and recombined to describe new categories, grounded recursively in the old ones. Such compression/expansion effects, called "categorical perception" (CP), have previously been reported with categories acquired by nsorimotor toil; we show that they can also ari from symbolic theft alone. The picture of natural language and its origins that emerges from this analysis is that of a powerful hybrid symbolic/nsorimotor capacity, infinitely superior to its purely nsorimotor precursors, but still grounded in and dependent on them. It can spare us from untold time and effort learning things the hard way, through direct experience, but it remain anchored in and translatable into the language of experience.
TOIL: GROUNDING LANGUAGE IN PERCEPTUAL CATEGORIES
红茶的好处
1. Language Evolution: A Martian Perspective
Whatever the adaptive advantage of language was, it was indisputably triumphant. If all our linguistic
capabilities were subtracted from the repertoire of our species today, very little would be left. Not only would all the fruits of science, technology and culture vanish, but our development and socialization would be arrested at the stage still occupied currently by the members of all other species, along with only the verely retarded members of our own. Buried somewhere among all tho undeniable benefits that we would lo if we lost language there must be a clue to what language’s original bonus was, the competitive edge that t us inexorably on our unique evolutionary path, distinct from all the nonspeaking species (Harnad, Steklis & Lancaster 1976; Steels 1997).
laidThere has been no scarcity of conjectures as to what that competitive edge might have been: It helped us hunt; it helped us make tools; it helped us socialize. There is undoubtedly some merit in such speculations, but it is hard to imagine how to test them. Language is famously silent in the archeological and paleontological record, requiring interpreters to speak for it; but it is the validity of tho very interpretations that is at issue here.
Perhaps we need to take a step back, and look at our linguistic capacity from the proverbial Martian anthropologist's perspective: Human beings clearly become capable of doing many things in their world, and from what they can do, it can also be inferred that they know a lot about that world. Witho
ut too much loss of generality, the Martian could describe that knowledge as being about the kinds of things there are in the world, and what to do with them. In other words, the knowledge is knowledge of categories: objects, events, states, properties and actions.
米勒斯Where do tho categories come from? A Martian anthropologist with a sufficiently long-range databa could not fail to notice that some of our categories we already have at birth or soon
ellen degeneres show
after, whereas others we acquire through our interactions with the world (Harnad 1976). By analogy with the concept of wealth, the Martian might describe the categories acquired through the efforts of a lifetime to be tho that are earned through honest toil, whereas tho that we are born with and hence not required to earn he might be tempted to regard as ill-gotten gains -- unless his databa was really very long-range, in which ca he would notice that even our inborn categories had to be earned through honest toil: not our own individual toil, nor even that of our ancestors, but that of a more complicated, collective phenomenon that our (ingenious) Martian anthropologist might want to call evolution.
So, relieved that none of our categories were acquired other than through honest toil, our Martian might take a clo look at precily what we had done to earn tho that we did not inherit. He would
find that the way we earned our categories was through laborious, real-time trial and error, guided by corrective feedback from the conquences of sorting things correctly or incorrectly (Catania & Harnad 1988). As in many cas the basis for sorting things correctly was far from obvious, he would note that our honest toil was underwritten by a substantial inborn gift, that of eventually being able to find the basis for sorting things correctly, somehow.
A brilliant cognitive theorist, our Martian would immediately deduce that in our heads there must be a very powerful device for learning to detect tho critical features of things (as projected onto our nsory surfaces) on the basis of which they can be categorized correctly (Harnad 1996b). Hence he would not be surprid that this laborious process takes time and effort -- time and effort he would call "acquiring categories by Sensorimotor Toil" (henceforth Toil).
Our Martian moralist would be surprid, however, indeed shocked, that the vast majority of our categories turn out not to be learned by Toil after all, even after discounting the ones we are born with. At first the Martian thinks that the unearned categories simply appear spontaneously; but upon clor inspection of his data he deduces that we must in fact be stealing them from one another somehow. For whenever there is evidence that one of us has acquired a new category without first having performed the prerequisite hours, weeks or years of Toil, in the laborious real-tim
e cycle of trial, error and feedback, there is always a relatively brief vocal episode between that individual and another one who has himlf either previously earned that category through nsorimotor Toil, or has had a very brief vocal encounter with yet another individual who has himlf either… and so on.sak
Without blinking, our Martian dubs this violation of his own planet's Protestant work ethic "the acquisition of categories by Theft," and immediately begins to arch for the damage done to the victims of this heinous epistemic crime. To his surpri, however, he finds that (except in very rare cas, dubbed "plagiarism," in which the thief fally claims to have acquired the stolen category through his own honest toil), category Theft ems to be largely a victimless crime.
Ever the brilliant cognitive theorist, our Martian would quickly discern that the mechanism underlying Theft must be related to the one underlying Toil, and that in principle it was all quite simple. The clue was in the vocal episode: All earthlings start with an initial repertoire of categories acquired by nsorimotor Toil (supplemented by some inborn ones); the categories are grounded by the internal mechanism that learns to detect their distinguishing features from their nsorimotor projections. The grounded categories are then assigned an arbitrary symbolic name (lately a vocal one, but long ago a gestural one, his databa tells him [Steklis & Harnad 1976]). This name remb
les neither the members of the category, nor their features, nor is it part of any instrumental action that one might perform on the members of the category. It is an arbitrary symbol, of a kind with which our Martian theorist is already quite familiar with, from his knowledge of the eternal Platonic truths of logic and mathematics, valid everywhere in the Univer, which can all be encoded in formal symbolic notation (Harnad 1990).
浪漫之吻
When our Martian analys more cloly the brief vocal interactions that always em to mediate Theft, he finds that they can always be construed in the form of a proposition that has been heard by the thief. A proposition is just a ries of symbols that can be interpreted as making a claim that can be either true or fal. The Martian knows that propositions can always be interpreted as statements about category membership. He quickly deduces that propositions make it possible to acquire new categories in the form of recombinations of old ones, as long as all the symbols for the old categories are already grounded in Toil (individual or evolutionary). He accordingly conjectures that the adaptive advantage of language is specifically the advantage of Symbolic Theft over Sensorimotor Toil, a victimless crime that allows knowledge to be acquired without the risks or costs of direct trial and error experience.
Can the adaptive advantage of Symbolic Theft over Sensorimotor Toil be demonstrated without the b
enefit of the Martian Anthropologist's evolutionary databa (in which he can review at leisure the videotape of the real-time origins of language)? We will try to demonstrate them in a computer simulated toy world considerably more impoverished than the one studied by the Martian. It will be a world consisting of mushrooms and mushroom foragers who must learn what to do with which kind of mushroom in order to survive and reproduce (Parisi, Cecconi & Nolfi 1990; Cangelosi & Parisi 1998). But before we describe the simulation we must introduce some theoretical considerations that are too fallible to be attributed to our Martian theorist: One concerns a fundamental limitation on the acquisition of categories by Symbolic Theft (the symbol grounding problem) and the other concerns the mechanism underlying the acquisition of categories by Sensorimotor Toil (categorical perception).
1.1.The Symbol Grounding Problem.纳尼亚传奇1
Just as the values of the tokens in a currency system cannot be bad on still further tokens of currency in the system, on pain of infinite regress -- needing instead to be grounded in something like a gold standard or some other material resource that has face-value -- so the meanings of the tokens in a symbol system cannot be bad on just further symbol-tokens in the system. This is called the symbol grounding problem (Harnad 1990). Our candidate for the face-valid groundwork of
meaning is perceptual categories. The meanings of symbols can always be cashed into further symbols, but ultimately they must be cashed into something in the world that the symbols denote. Whatever it is inside a symbol system that allows it to pick out the things its symbols are about, on the basis of nsorimotor interactions with them (Harnad 1992; 1995), will ground tho symbols; tho grounded symbols can then be combined and recombined in higher-level symbolic transactions that inherit the meanings of the ground-level symbols. A simple example is "zebra," a higher-level symbol that can inherit its meaning from the symbols "striped" and "hor," provided "striped" and "hor" are either ground-level symbols, or grounded recursively in ground-level symbols by this same means (Harnad 1996a).limitededition
The key to this hierarchical system of inheritance is the fact that most if not all symbolic expressions can be construed as propositions about t (i.e., category) membership. Our
