6.1 What do we mean by Common Sense?

“Common sense is the collection of prejudices acquired by age eighteen.”—Albert Einstein

Instead of blaming machines for their deficiencies, we should try to endow them with more of the knowledge that most people have. This should include not only what we call “commonsense knowledge”—the kinds of facts and theories that most of us know— but also the commonsense kinds of reasoning skills that we accumulate for applying that knowledge.

Student: Can you more precisely define what you mean by ‘commonsense knowledge’?

We each use terms like ‘common sense’ for the things that we expect other people to know and regard as obvious. So it has different meanings for each of us.

Sociologist: What people regard as obvious depends on their communities. Each person lives in several of these—such as family, neighborhood, language, clan, nation, religion, school, and profession—and each of these ‘clubs’ shares different collections of knowledge, beliefs and ways to think.

Child Psychologist: Still, even if you know only a child’s age, you can say much about what that child is likely to know. Researchers like Jean Piaget have studied children all over the world and found that their minds grow in similar ways.

Citizen: We sometimes say people lack 'common sense’ when they do things that seem foolish to us—not because they are lacking in knowledge, but that they’re not using it properly.

We are constantly learning, not only new facts, but also new kinds of ways to think. We learn some from our private experience, some from the teaching of parents and friends, and some from other people we meet. All this makes it hard to distinguish between what each person happens to know and what others regard as obvious. So, what each person knows (and their ways to apply it) may differ so much that we can’t always predict how others will think.

We tend to take commonsense thinking for granted, because we do not often recognize how intricate those processes are. Many things that everyone does are more complex than are many of those ‘expert’ skills that attract more attention and respect.

The Telephone Call.

“You cannot think about thinking without thinking about thinking about something.” —Seymour Papert

We’ll start by following Papert’s advice—by thinking about some ways to think about this typical commonplace incident:

“Joan heard a ring, so she picked up her phone. Charles was answering a question she asked about a particular chemical process. He advised her to read a certain book, which he will shortly bring to her, since he will be in her neighborhood. Joan thanked him and ended the call. Soon Charles arrived and gave her the book.”

Each phrase of that story evokes in your mind some of these kinds of understandings:

Joan heard a ring. She recognizes that this special sound means that someone wishes to speak with her.

She picked up the phone. Compelled to respond, she crosses the room and moves the receiver to her ear.

Charles was answering a question she asked. Charles is in a different room. They both know how to use telephones.

He advised her to read a certain book. Joan understands what Charles has said.

Joan thanked him. Was that just a formality or was she genuinely grateful to him?

He’ll soon be in her neighborhood. Joan won’t be surprised when he arrives.

He gave her the book. We don’t know if this was a loan or a gift.

We draw these conclusions so fluently that we don’t even know that we’re doing it. So let’s try to examine how much is involved when one understands what happened when Joan heard that sound and picked up that phone.

First, when Joan looks at her telephone, she sees only a single side of it, yet she feels that she’s seen the entire thing, And even before she reaches for it, she anticipates how it will fit in her grasp, and how it will feel when it contacts her ear, and knows that one speaks into here and hears answers from there. She knows that if she dials a number, some other phone will ring somewhere else—and if anyone happens to answer it, then those two persons can start to converse.

All this rapid retrieval of knowledge seems a natural aspect of seeing an object—and yet, one has only detected some patches of light! How does such scanty evidence make it seem as though what you’re ‘looking at’ has been transported right into your mind—where you can move it and touch it and turn it around—or even open it up and look inside? The answer, of course, is that what you ‘see’ does not come from your vision alone, but also from how those visual clues lead you to retrieve other knowledge.

However, on the other side, you know so much about such things that, surely, your mind would be overwhelmed if you had to ‘attend’ to all that knowledge at once. So our next few sections will be discuss how brains might interconnect fragments of knowledge so that we can often retrieve just the ones that we need.

The concept of a ‘Panalogy.’

“If you pluck an isolated sentence from a book, it will likely lose some or all of its meaning—i.e., if you show it out of context to someone else, they will likely miss some or all of its intended significance. Thus, much of the meaning of a represented piece of information derives from the context in which the information is encoded and decoded. This can be a tremendous advantage. To the extent that the two thinking beings are sharing a common rich context, they may utilize terse signals to communicate complex thoughts.”—Douglas Lenat

Every word, event, idea, or thing can have many different meanings to us. When you hear, "Charles gave Joan the book,’ that might make you think of that book as a physical object, or as a possession or possible gift. And you could interpret this ‘giving act’ in at least these three different realms of thought:

The Physical Realm: Here 'give’ refers to the book’s motion through space, as it moves from Charles’ hand to Joan’s.

The Social Realm: One might wonder about Charles’ motivation. Was he just being generous, or hoping to ingratiate himself?

The Dominion Realm: We may infer that Joan is not only holding that book, but also has gained permission to use it.

That “Dominion” realm” is important because we need it to achieve our goals. You cannot solve problems or carry out plans without adequate tools, supplies, and materials—but most of the things in our civilized world are controlled by persons or organizations that won’t allow you to use those things until you get permission to do so. So gaining control or authority is often a requirement for (or an obstacle to) achieving some other goal.

Similarly, when two children are playing together with blocks, each may have concerns in many different mental realms:

Physical: What if I pulled out that bottom block?

Social: Should I help him with his tower or knock it down?

Emotional: How would he react to that?

Mental: I forgot where I left the arch-shaped block.

Bodily: Can I reach that arch-shaped block from here?

Visual: Is the long flat block hidden behind that stack?

Tactile: What would it feel like to grab three blocks at once?[1]

Spatial: Could I arrange them into the shape of a table?

What happens when you select an inappropriate realm of thought, in which to interpret a certain event? Then almost instantly after you notice this, you switch to a relevant point of view, without any sense of starting over again. How do we do this so rapidly? In §8-3 I will argue that our brains may use special machinery that links corresponding aspects of each view to the same ‘role’ or ‘slot’ in a larger-scale structure that is shared across several different realms. We’ll call such a structure a “Panalogy” (for Parallel Analogy) and will discuss this more in §8-3. [2]

Three meanings of ‘give.’

We again see how a thing or idea can be viewed as having multiple meanings. We sometimes call these ‘ambiguities’ and regard them as defects in how we express or communicate. However, when these are linked into panalogies, then when situations don’t seem to make sense, we can think about them in alternative realms—without the need to start over again. Shortly, we’ll outline a similar scheme to explain how our vision could work so speedily.

Student: You’re suggesting that we use the same techniques to represent transportation in space, for transferring an ownership, and for transmitting knowledge to other brains. But what could have led our minds to treat such different ideas in such similar ways?

It surely is no accident that our language uses the same prefix ‘trans’ in transfer, transport, transmit, translate, transpose, etc., —because that common word-part ‘trans’ induces us to make many widely useful analogies.[3] Each of us knows thousands of words, and as each time we learn how others use one of them, we inherit another panalogy.

Student: How many different realms can a person use for any particular concept or object? How many of them can we handle at once? How does one know when it’s time to switch? To what extent do different persons partition their worlds into similar realms?

More research on semantics will eventually clarify questions like these, but the following sections will only discuss a handful of realms that are familiar to everyone.

Sub-Realms of the Telephone World

We’ve mentioned only a few of the things that every telephone user knows. However, to use what you know about telephones, you also have to know how to speak, and to understand some of what you may hear. You also need a good deal of knowledge about what people are and how they think, so that you can turn their interests toward the subjects that you want to discuss. Consider how many different knowledge-realms we engage to understand the story about Joan’s telephone call.

The Spatial Realm: Joan is close to her telephone, but Charles must be in some more distant place.

The Dominion Realm: Both Joan and Charles have telephones, and Charles has dominion over that book. But we can’t be quite certain of which ones they own.

The Procedural Realm: How does one make a telephone call? We could represent this in terms of a script in which certain actions are specified, but others require you to improvise.

First, you must find the phone and dial a number. Then, once the connection has been established, you're supposed to begin with some pleasantries. Eventually, you should say why you called—and then depart from the typical script. At the end you'll close the conversation by saying “goodbye” and ‘hanging up’. Generally, such behavioral scripts begin and end with conventional steps, with improvisations in between. However, you’ll have to depart from the script if something goes wrong—and know how to deal with a wrong connection, or what to do if there is no answer, or if you hear the whine of a modem—or if there is too much noise on the line.

The Social Realm: When that telephone rings from across the room, Joan will have to walk over to get it; she knows it will do no good to ask, “Telephone, would you please come here!” To make an inanimate object move, you have to push, pull, or carry it. But if you want a person to move, those actions would be considered rude; instead you’re expected to make a request. It takes our children quite a few years to learn enough such social rules.

The Economic Realm: Every action incurs some cost—not only in materials, time, and energy, but also by closing off alternatives that might bring different benefits. This raises questions about how much effort and time one should spend at comparing the costs of those options. I suspect that there’s no simple answer to that, because it depends so much on the present state of the rest of one’s mind. [See §§Free Will.]

The Conversational Language Realm: Most people are experts at dialog, but consider how complex are the skills involved in a typical verbal exchange. You must constantly keep track of the topic, your goal, and your social role. To maintain the respect of your listeners, you must guess what they already know and remember what has already been said—so that you won’t be too repetitive. It is annoying to be told things one already knows, like “People can’t see the backs of their heads,” so your conversation must partly be based on your models of what your listeners know about the subjects that are being discussed.

You can communicate your apprehensions and hopes—or try to disguise your intentions; you know that every expressive selection can strengthen or weaken social bonds; each phrase can persuade or intimidate, conciliate or irritate, or ingratiate or drive away. You also need to keep searching for clues about how well they have understood about what you’ve said—and why you were trying to tell them those things.

Humanist: Speaking over a telephone is a poor substitute for a face-to-face exchange. The telephone lacks the 'personal touch' through which your gestures can put the others at ease, or express the strength of your feelings.

One always loses some nuances when conversing with a person at some other location.’ On the other side, we're not always aware of the misconceptions that result from what we call 'face-to-face' interactions. What if the stranger that you have just met should resemble (in manner or facial appearance) some trusted friend or some enemy? If that person reminds you of some old Imprimer, this can arouse a misplaced affection or unjustified sense of intimidation. You may think you can later correct such mistakes—but one can never completely erase the ‘first impression’ that one makes.

We also all share many abilities that we don’t usually call ‘commonsensical”—such as the kinds of physical skills that Joan uses to answer that telephone call:

The Sensory and Motor Realms: It takes less than a single second for you to reach out your arm and “Pick up the phone" —yet consider how many sub-goals this involves:

Determine the telephone’s location.

Determine its shape and orientation.

Plan to move your hand to its place.

Plan how your hand will grasp its shape.

Plan to transport it toward your face.

Each step of that script raises questions about how we do those things so quickly. We can program computers to do such things, but we do not know how we do them ourselves. It is often supposed that such actions are done under continuous ‘feedback control’—by processes that keep working to reduce your distance from your goal. However, that cannot be generally true because human reactions are so slow that it takes about one-fifth of a second to react to events that one did not expect. This means that you cannot change what you are doing right now; all you can do is revise the plan that you’ve made for what you will do after that. Thus when Joan reaches out to answer that call, she must plan to reduce the speed of her hand—and to already have reshaped her hand—before it collides with that telephone. Without good plans for what will happen next, she’d be constantly having accidents.

Kinesthetic, Tactile, and Haptic Realms: When you squeeze your phone between shoulder and cheek, you anticipate its texture and weight, adjust your grip so that it won’t slip, and expect those pressures to disappear as soon as you release it. You already know that this object will fall if released from your grasp, or will break when subjected to too large a stress An immense amount of such knowledge is stored in your spinal cord, cerebellum, and brain—but those systems are so inaccessible that we can scarcely begin to think about them.

• Cognitive Realms: We are almost equally inept at describing the systems we use when we think. For example, we are almost completely unaware of how we retrieve and combine the various fragments of knowledge we need—or of how we deal with the risks of being wrong when these involve uncertainties.

The Self-Knowledge Realm: Whatever you may be trying to do, you’ll need models of your own abilities. Otherwise, you’ll set goals that you’ll never achieve, make elaborate plans that you won’t carry out, or too frequently switch between interests—because, as we’ll see in §9 Self, it is hard to achieve any difficult goals unless one can make oneself persist at them.

It would be easy to add to this list of realms, but hard to construct clear distinctions between them.

Remembering

We discussed how much knowledge a person could have, but perhaps it is more important to ask how we re-collect what we need so quickly when we need it?

Whenever we get a new idea, or find a new way to solve a problem, we may want to make a memory-record of it. But records are useless unless you have ways to retrieve the ones most likely to be relevant to the problems you face. I’ll argue that this needs a lot of machinery.

Citizen: If remembering is so complex, then why does it seem so effortless, simple and natural? Each idea reminds me of similar ones, which then make me think of related ideas—until I recall the ones that I need.

Why does ‘remembering’ seem so effortless? As long ago as you can remember, you could always recall things that happened to you. However, you cannot remember much of your earliest years; in particular, you cannot recall how you developed your early abilities. Presumably, you had not yet developed the skills one needs for making those kinds of memories.[18]

Because of this Amnesia of Infancy, we all grow up with simplistic views of what memories are and how they work. You might think of your memory as like a writing-pad, on which you can jot down mental notes. Or perhaps for each significant event, you store ‘it’ away in some kind of memory-box and later, when you want it back, you somehow bring ‘it’ out of that box—if you are lucky enough to find it. But, what kinds of structures do we use to represent those ‘its’ and how do we bring them back when we need them? Our recollections would be useless unless (1) they are relevant to our goals and (2) we also have ways to retrieve the ones that we need at the times when we need them.

To do this, a computer expert might suggest that we store everything in some single ‘data base’ and use some general-purpose ‘matching’ technique. However, most such systems still classify things in terms of how they are described instead of what they are likely to be useful for. The trouble with this is we do not usually know what kind of thing we are looking for, but only what we want to accomplish with it—because we’re facing some obstacle, and want to know how to deal with it.

So, instead of using some ‘general method, I suspect that every child develops ways to link each new fragment of knowledge to goals that it might help us to achieve, as well as to other related ideas. These additional links might help to answer questions like these:

What kinds of goals might this item serve? Which kinds of problems could it help to solve? What obstacles could it help to overcome? In which situations might it be relevant? In which contexts is this likely to help? What subgoals must first be achieved? How has it been applied in the past? What were some similar previous cases? What other records might be relevant? See §8-Credit Assignment.

Each fragment of knowledge may also need links to some knowledge about its deficiencies—and the dangers and costs of using it:

What are its most likely side effects? Is it likely to do us more harm or more good? How much will it cost to use it? Will it repay the effort of using it? What are its common exceptions and bugs? In which contexts is it likely to fail us—and what might be good alternatives? Is it part of some relevant family? [See Glossary: Ontology.]

We also link each item to information about its sources and to what other persons might know.

Was it learned from a reliable source? Some informants may simply be wrong, while others may mean to mislead us. Is it likely to be outdated soon? That’s why this book does not depend much on current beliefs about how our brains work. Which other people are likely to know it? Our social activities strongly depend on knowing what others may understand.

All this raises question about how we make so many connections to and from each new fragment of knowledge. I suspect that we can’t do this all at once—and indeed there is some evidence that it normally takes some hours or days (including some sessions of dream-laden sleep) to establish new long-term memories. Also, we probably add more links each time we retrieve a fragment of knowledge, because then we’re likely to ask ourselves, “How did this item help (or hinder) me at overcoming this obstacle?” Indeed, some research in recent years suggests that our so-called long-term memories are not so permanent as we used to think; it seems that they can be altered by suggestions and other experiences.

We all know that our memory systems can fail. There are things that we can’t remember at all. And sometimes we tend to recollect, not what actually happened to us, but versions that seem more plausible. At other times we fail to remember something relevant until—after several minutes or days—suddenly the answer appears—and you say to yourself, “How stupid of me; I knew that all along!” (That could happen either because an existing record took long to retrieve, or because it was never actually there, and you had to construct a new idea by using some process of reasoning.)

In any case, we should expect such ‘lapses’ because our recollections must be selective; §4-4 discussed how bad it would be to remember everything all the time: it would overwhelm us to recall all the millions of things that we know. However, none of this answers the question of how we usually retrieve the knowledge that we currently need. I suspect that this is mainly due to our already having prepared in advance the sort of links discussed above. But constructing these requires additional skills; we’ll discuss these in §8-5 Credit Assignment.

As the start of this section we asked about how we retrieve the knowledge we need. The following section will argue that part of the answer lies in those links to the goals that each fragment of knowledge might help to achieve.” To make that statement more concrete, the next few sections will investigate what goals are and how they work.