Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!cbatt!ihnp4!inuxc!pur-ee!uiucdcs!uiucuxc!uiucme!keith From: keith@uiucme.UUCP Newsgroups: net.cog-eng Subject: knowledge and design Message-ID: <11800012@uiucme> Date: Wed, 1-Oct-86 15:28:00 EDT Article-I.D.: uiucme.11800012 Posted: Wed Oct 1 15:28:00 1986 Date-Received: Sat, 4-Oct-86 11:45:26 EDT Lines: 92 Nf-ID: #N:uiucme:11800012:000:4654 Nf-From: uiucme.UUCP!keith Oct 1 14:28:00 1986 Naive Physics and Competent Design Twelvth of a series {after a longish hiatus} P. Hayes has in a number of different papers proposed a reasoning problem known by the name, "naive physics". The concept is fairly simple: when we play tennis we don't solve vector sums to get to where we can hit the ball, how to hit the ball, where it will travel, how it will bounce. Speaking from personal experience, how do I know I'll never get there in time to hit the ball, so there's no point in trying? We have through experience developed some form of understanding of the physics of the world around us. I am learning a great deal about physics from my two-year-old daughter (see also: propogation of roommates). She doesn't know some of the things I know, and it's sometimes frustrating as she has to discover these things for herself. Why can't she crawl through the same opening the cat just did? What is it about doorknobs that makes them hard to turn when they're locked? I'm learning to appreciate just how much I know which I'm not concious of knowing. So how are two-years-olds and proposed a.i. problems related? Well, the reasoning behind the proposal is that by understanding the reasoning we use to deal (intuitively?) with everyday physics problems, we can develop a better understanding of what is called common sense. After naive physics comes naive economics, naive law, and eventually (next Christmas) we will have succeeded in building a consolidated model of how people (in general) solve problems (in general). An area of naive physics that recieved some examination is the behavior of fluids. To connect this directly to your personal experience, I will discuss a particular behavior-of-fluids problem I am presently researching with the assistance of my daughter. When you pick something up on a spoon, why does or doesn't it fall off? I suggest you carry out some experiments, either in thought or with appropriate lab equipment, as you follow along through the related questions. What is it about pudding that it only falls off slowly? What is it about macaroni and cheese that it almost never falls off? What is it about soup and cereal that part will fall off, but part may stay on the spoon? Is there any correlation between the orientation of the spoon's bowl the the tendency to fall off? Is there any correlation between the speed with which the spoon is moved and the tendency to fall off? Why do some things stay level (like broth) and some things pile up (like pudding), and some things pile up a lot (like macaroni and cheese). Is there any correlation between the ability to pile up on the spoon and the tendency to fall off? I leave the answers to these questions as an exercise for the reader. But there are some interesting points to notice: - Your answers, in a triumph of the intellect, can run into concepts like viscosity, surface attractions, gravity, and the tendency to continue travelling in a straight line (centrifugal "force"). My daughter {italics} will know the answers without knowing how to define any of these terms {end of italics} after a few years additional exposure to the experiments. (Dinner time is learning time). - These questions are explored in three daily events that total roughly an hour per day and only a few minutes of actual experience with the problems per day. How long (in time, and labor-time) by heavily- educated researchers would it take to reach a level of understanding held by almost every five-year-old? - In an application to my own area of interest, what has been developed can reason about fully-described situations. But design is the act of conceiving of situations that have not been described, then developing the description. To what extent can the same knowledge, or even the same kind of knowledge, be applied to this class of problem? Darn. Now it looks like I'm criticising the concept of naive physics. Actually, as areas of research in a.i. go, naive physics is an interesting, promising area that addresses some core questions in cognition and modeling cognition on the computer. But it is essential that we recognize the limits of a model, rather than accepting the model's results at face value and resenting reality for failing to cooperate. keith U of Illinois Mech Eng seismo!ihnp4!uiucdcs!uiucme!keith In what can only be described as a deliberate attempt to alienate the audience, next postings will consist of a series of complaints: - knowledge representation problems - the limits of models - the assumption of rationality - can an analysis tool help design?