Did you know ... Search Documentation:
Pack logicmoo_nars -- ImportantDocs/jmc/child-sli.md

THE WELL-DESIGNED CHILDJohn McCarthy

Stanford University

jmc@cs.stanford.edu

http://www-formal.stanford.edu/jmc/September 28, 2007

  • • The world into which a human is born is complex. W
  • discuss some of the complexities, concentrating on one—
  • 3-d semi-permanent, movable objects.
  • • Evolution has equipped a baby with some innate kno
  • edge of the world. That works better than starting as
  • blank slate.
  • • Consider a well-designed logical robot child (WDC).
  • Mostly it will have the innate abilities we conjecture real
  • children have, but sometimes we can do better. THE LOCKEAN BABY
  • • John Locke 1693: The baby starts out as a blank slate.
  • It builds its knowledge by inferring associations among
  • stimuli.
  • • Since 1950 people proposed to start with a Lockean
  • blank slate baby machine and have it learn from its exp
  • rience.
  • • Starting from the blank slate, I’ll bet it’s a lengthy
  • process to infer the existence of 3-d objects. I don’t- think anyone has made an AI system that can do it.
  • • A billion years of evolution has provided us with prett
  • good prejudices about the world far better than a blank
  • slate. Our robot child should also have them THE WORLD IS COMPLICATED- • The world’s structure is not directly describable in terms
  • of the input-output relations of a person. The basic struc-
  • ture of the world involves elementary particles on time
  • scales of 10−25 seconds, but intelligence only evolved
  • structures of more than 1023 elementary particles.
  • • Even at the level at which a small child can perceive
  • the world is extremely complicated. Here are some of
  • complications.
  • • Reality and appearance Animals and humans don’t p
  • ceive the structure of our environment directly. Senses
  • have evolved to give partial information about objects- and their relations.
  • • The world is 3-d, but our senses react to surfaces. MORE COMPLICATIONS
  • • semi-permanent objects Much of the world consists
  • three-dimensional objects that have masses, moments,
  • compliances, hardnesses, chemical composition, shap
  • outer surfaces with textures and colors, are often made
  • identifiable parts which sometimes move relative to each
  • other. A particular object can disappear from perception
  • and reappear again.
  • Note that the structure and location of an object in
  • world are more persistent than its appearance and lo
  • tion in the visual field or relative to the hands.
  • • temporal structure The environment of a child has
  • complex temporal structure. Some items change in sec-
  • onds, others last for hours, days, or years. Babies
  • in the present. The concepts of tomorrow and yesterda
  • are not learned right away.
  • • causality Events cause changes in objects and their
  • lations and cause other events. STILL MORE COMPLICATIONS- • solidity Objects are solid and do not ordinarily penetrate
  • one another. Some are rigid and some are flexible.
  • • gravity Unsupported objects fall to a lower surface.
  • • kinds of objects Objects have kinds, and objects
  • the same kind have properties associated with the kind.
  • Babies are ready very early to learn what kinds there a lemons, belong to natural kinds. The objects of- • natural kinds Many of the objects a child encounters,
  • e.g.
  • natural kind have yet undiscovered properties in common.
  • Therefore, a natural kind is not definable by an if-and-
  • only-if sentence formulated in terms of observables.
  • • relations Objects not only have individual properties
  • and belong to kinds, but objects and kinds have relations
  • with one another. At least some ternary relations such
  • as betweenness are basic. Also “A is to B as C is to
  • seems to be basic. In its numerical use, it reduces- the equality of two fractions, but the quaternary relation
  • seems to be basic in common sense usage. WHAT DO BABIES KNOW AND WHEN?- • Q: If the world is so complicated, how can babies
  • anything purposeful?
  • • A: They know simple cases of phenomena.
  • • There’s good psychological evidence that they have
  • innate knowledge of solid objects that continue existing
  • even when out of sight. How do they remember an object
  • that has gone out of sight so as to recognize it when
  • reappears?
  • • They are ready to ascribe purposeful action to humans
  • and animals and to try to influence them.
  • • the principle of mediocrity (from the astronomers) Our
  • child is like other children. This lets it reason in b
  • directions.
  • • persons Some objects are animate and have purposes
  • analogous to those of the child. They can be influenced
  • but are sometimes to be feared. Defects in innate under-
  • standing of persons, e.g. autism, harm the child. WHAT DO WE WANT IN A WELL-DESIGNEDROBOT CHILD?
  • • Distinguish appearance from reality
  • • natural kinds Natural kinds don’t have if-and-only-if def-
  • initions. There may always be more properties to
  • learned. To a small child, all kinds are natural. The
  • robot child should think in terms of natural kinds.
  • • three-dimensional objects These are more stable than
  • the perception of them by any sense.
  • • perceive motion as continuous
  • • actions and their effects
  • • recognize parts Recognize parts of an object and their
  • relations to the others. It would be interesting to have
  • grammar of 3-d physical structure analogous to that
  • sentences.
  • • focussed curiosity
  • • grammar of goal regression To do A, I need to do
  • first, and to do B, I need to do C first.
  • • introspection Children begin to do this by age 3, do
  • well by age 5. The WDC needs it. THE SPELKE EXPERIMENT- This psychological experiment exhibits abilities of human
  • babies we want in the WDC.
  • Elizabeth Spelke described a number of experiments that
  • she and others did to discover and verify innate mental
  • abilities. The technique uses the fact that a baby
  • look longer at something surprising than at something
  • that seems familiar.
  • Here’s one that was first done in 1973 and was repeated
  • by Spelke in 1993 with two months old babies. There
  • are experimental babies and control babies and the
  • periment has two phases.
  • babies are shown nothing. The experimental babies In the first phase the control- an object go behind a screen and shortly another object
  • emerges on the other side of the screen. The timing
  • such as would be appropriate if the first object struck
  • the second object and knocked it from behind the screen.
  • The babies are shown the phenomenon enough times
  • get bored with it and stop paying attention.
  • In the second phase of the experiment the screen is
  • moved. There are two variants. In the first variant,
  • first object strikes the second and knocks it onward.
  • the second variant the first object stops short of the sec-
  • ond, but the second object takes off as though it had
  • been struck. The control babies look at both variants
  • the same amount of time. The experimental babies lo
  • longer at the second variant.
  • The conclusion is that the experimental babies inferred
  • that the first object had struck the second when the event
  • occurred behind the screen. When the screen was
  • moved, they were not surprised when the expected event
  • was shown to occur but were surprised and looked longer
  • when this expectation was not met.
  • The conclusion is that babies have innate expectations
  • about dynamics. For details see Spelke’s 1994 article
  • Cognition, Initial knowlege: six suggestions. THE WELL-DESIGNED CHILD AS A LOGICALROBOT
  • • Not even a sketch of a design—just some ideas.
  • • Appearance and reality
  • Appears(appearance, object) is too simple except in a lim-
  • ited context, but children think in limited contexts.
  • Holds(Appears(person, appearance, object), s) says more
  • is suitable for referring to the child from the outside. CONTEXTS
  • • The correctness of a child’s beliefs and references
  • objects depends on context. Children change context
  • frequently.
  • • When looking at a child’s ideas from the outside,
  • can use the theory of contexts as objects introduced
  • my Notes on formalizing context. In that theory Ist(c, p
  • true if the proposition p holds in the context c. V alue(c,
  • is the value of the expression exp, e.g. Color(Block1),
  • context c.
  • • V alue(Belief s(Child1, S0), Color(Block1)) = Red asserts
  • that in the context of Child1’s beliefs in situation s, Blo
  • is red. The context theory lets us enter the context
  • Belief s(Child1, S0). Then we have Color(Block1) = R THREE CHALLENGES AND A CONCLUSION- • Make a robot baby that can do the Spelke experiment
  • honestly. But what’s honestly? It may start knowing
  • about collisions and knowing about occluded objects,
  • at least it shouldn’t start with knowledge combining
  • two.
  • • Its contexts should change like those of a baby.
  • • It should properly relate 2-d appearances to 3-d realit
  • and also relate tactile appearances to reality. Here’s
  • puzzle.
  • • What babies know presents challenges to AI—to AI
  • all schools.
  • • This talk is partly based on the manuscript
  • http://www-formal.stanford.edu/jmc/child.html.