What is a behavior?

Then it's not a behavior because even outside robotics, behaviors are the REACTION to some stimulus.

To that end, there really is no such thing as ANY object in this universe that merely acts -- has just an output. Everything has a cause and effect. If you separate cause from effect then you have defined some other system that should have its own term, but it's not behavior-based robotics.

-- Gordon

Hi,

Jones definition of behavior is dictated by the requirements of implementing the subsumption priority algorithm. It is not intended, I think, as a generic definition in the sense that you are defining it.

A "behavior" as in "Behavior Based Robotics" is based on an underlying subsumption-style architecture which requires a trigger to determine when a behavior output is active, and therefore subsuming any lower priority behaviors, and when the output is inactive, and therefore allowing lower priority behaviors to control the robot.

Without the triggers, only the highest priority behavior would ever control the robot. It would never "release" control. A particular low priority behavior only controls the robot when all of the higher priority behaviors are inactive -- i.e., not triggered.

The triggers are an integral part of the subsumption process.

dpa

RMDumse wrote:

I disagree, and offer this argument in rebutal.

On page 52 Jones lists "Cruise" as a primitive behavior. He readily admits it has no trigger, or if it did, it would be constantly stuck on. So I think he is self coontradictory saying all primitive behaviors have triggers, then offering one without a trigger.

I did say I think a behavior should be defined to be an output action, usually based on a transform sensory information.

The reason I said "usually" about being a transform of input stimuli, the other thing Cruise doesn't have is anything to react to. It is simply a constant applied to the outputs with no regard to any input. It may terminate, but subsumptions terminates it, while Cruise itself continues to suggest a constant output.

Behaviors can be reactions to stimuli. But that doesn't mean the behavior IS the reaction to stimuli. For instance, if one stimuli can evoke two behaviors under different times and circumstances, the behavior has to be considered separate from the stimuli that caused it to be invoked. Also if two stimuli can evoke a single behavior, then the behavior must in some sense be independent of the trigger that evoked it.

(If I stub my toe, or if I look at my property taxes I get angry. The triggers are independent of the anger behavior, but the anger behavior being hopping mad with release of adreniline, increased pulse, reddening of the face, tightening of the lip, etc., is identical in both cases.)

The trigger is not he behavior. & Not all behaviors have inputs signal inputs.

-- Randy M. Dumse

In context, I think it was intended to be a generic definition. It is at the opening of Ch3 titled Behaviors and is worded ""Primitive behaviors, as we use the term in behavior-based robotics".

This is only the case for one type of arbitration. Jones shows many possible ways to arbitrate behaviors, and Arkin even more. In fact, Jones Ch 4 is all about arbitration, and Brooks subsumption method is only one, listed as a minor heading under "Other Arbitration Schemes" on pg 93.

I very much agree with this comment. But triggers are an integral part of the subsumption process, does not mean triggers are an integral part of the behaviors subsumed in the subsumption process..

-- Randy M. Dumse

That's right. It's simple physics. All action (behavior) is motion of matter. All motion represents the transfer of energy. Energy is conserved, so in this universe, you can't have an action without a cause. The energy that caused the action, had to some from somewhere.

A trigger is nothing more than another sensory input. It's just that in that context, it's common to have a separate input that works as an enable input. Whether you call it a trigger or a sensor is arbitrary. They simply find it convenient to think of it as a trigger apparently.

For example, an AND gate with two inputs can also be thought of as a data switch with one data input and one enable signal. It's the same device either way you think about it. Neither way of describing it is right and neither way is wrong. It's just two alternate ways to describe the same thing.

It seems to me you are working too hard to try and understand what a behavior is. Behavior is just a word. Behaviors are not the things you need to understand. The hardware is what you need to understand. If you understand it, at all levels of abstractions, then you know all you need to know.

That is not so. All the schemes described in Jones chapter 4 use the same basic structure: a series of behaviors feeding an arbiter.

If the higher priority behaviors never releases the arbiter, none of the lower behaviors can control the robot. That's how the arbiter works. The sole exception to this is the "motor schema" method.

This is why each "behavior" as in "Behavior Based Robotics" must include a threshold of some sort and a trigger, such that at some times it asserts its outputs and subsumes other, lower-priority behaviors, and at other times it does not. That arbitration is the very core of behavior-based robotics.

dpa

So all behaviors have actions? and there are no behaviors without action?

(I would tend to agree, but I want to be certain there isn't some odd circumstance where a behavior doesn't have an action. I haven't explored all cases. It might be that something like reaction to hidden anger, a newly formed grudge, isn't externally expressed, but then, I'd be inclined to argue that it is a change of state, and something added to memory, for future reference in selecting future behaviors.)

-- Randy M. Dumse

Pg 103 last bullet in the summary Jones says, "Other types of arbitration schemes include variable priority, motor schema, and least commitment." And as mentioned Arkins discusses many other possible ways to combine behavior. "Motor schema" is far from the sole exception.

But this is largely my point.

Fixed priority comes from having a trigger that requests control at a fixed level, and a trigger comes from the necessiry of having fixed behavior to assign a level.

If you have a trigger built into the behavior, you don't need an intelligent arbiter. You simply have the highest priority winning. The arbiter is completely deterministic by its wiring, and therefore unintelligent. The intelligence is built into the behavior in the form of the trigger, and the wiring priority to the arbiter.

In other schemes, the arbiter can be intelligent, choosing priorities based on other inputs, state, learning; or even caprice for the sake of learning, for that matter. (My reaction is to suggest behaviors and learning are incompatible, that is, behaviors are chosen based on learning, not that behaviors are modified based on learning.)

Now I will acuse you of being lead by your bias. Because you assume a fixed arbitration scheme as the only one valid, you insist a trigger must exist in the behavior. If you allow for other than fixed arbitration, then the trigger belongs outside the behavior, either as a stand along component, or possibly in the arbiter.

I see the more general case being behavior and trigger being separate items which when lumped into one allow only for one easily useful arbitration scheme: fixed priority.

-- Randy M. Dumse

If I someone said the distributor is part of the transmission, because it is taken off a gear train, would it matter? Transmission is just a word, transmissions are not things you need to understand, the drive train is what you need to understand. ... Yet, funny, when I take the transmission off the engine, the engine won't run and I can't test it separate from the rest of the drive train.

Similarly, wether the trigger belongs in the behavior or the arbiter is important so we can understand the hardware at all levels of abstraction. Otherwise we are prone to errors in understanding, and run into troubles in our ability to build and demonstrate working replicas.

My interest here is in identifying intelligence. If it has been accidentally grouped with behavior, when it should have been grouped with arbitration, then we have hidden AI from ourselves by not being critical of our definitions and subdivisions of the problem.

Prof. Ron Arkin has been kind enough to make a comment to an email request:

Behaviors mean different things to different people, depending on where their community lies. My work has been heavily influenced by ethology and psychology and thus I draw from those communities for my definitions. Engineers have a different stance. No one is right or wrong, they just have different meanings from one group to the next. That's what's particularly hard about interdisciplinary research, in getting the language/semantics correct between different groups. You may be encountering some of that here.

I'll stick with my definitions which appear on page 24 of my book.

My point is Randy you are taking an established field of endeavor, with its own definitions, and trying to rewrite it. You're insisting a "behavior" is something that can be quantified simply by mechanical means (an input or output), rather than an observable whole event, as was originally described by Brooks. I think you're missing something very basic, and can only recommend a more thorough reading back to Brooks. Brooks is pretty clear that a behavior must have an input. (Even his "wander" behavior, which is undefined by its nature, is not inputless.)

Your statement on inputs: "But that doesn't mean the behavior IS the reaction to stimuli" is a non-sequitor. A behavior is a reaction. A reaction is to some action -- if you don't like that definition, take it up with Sir Isaac. Synonyms for action: stimumus, trigger, input. True enough, some behaviors are caused by multiple stimulus, but that still means an input is required.

I think it's okay to redefine an approach, but call your system something else, rather than trying to turn around existing and accepted methodology. The problem of people redefining the same terms to mean different things is part of the reason AI keeps getting stuck. If people can't agree on the terms, they certainly cannot agree on anything else.

So, might I suggest for input-less actions we start calling the system Randysian. Anything but behavior-based.

As an aside, anger is not a behavior, it is an emotion. This is a common mistake in Brooksian BBR. A behavior that reflects anger would be smashing your fist on the table, or punching your CPA in the face and telling him he's screwed up agrain. By itself, anger and other emotions can have no observable output, and in Brooksian behavioralism, without being able to observe it, there is no behavior. Only what we can OBSERVE is relevent. Otherwise it gets into issues of sapience that hopelessly complicates matters.

-- Gordon

RMDumse wrote:

But that is more or less the problem, where are those established definitions?

Brooks describes "behaviors" as "task acomplishing" pg 4 Cambrain Intelligence. Other than that, there is no solid definition. I've quoted Jones definition in the opening post, and made comments about how I think Jones then contradicts his own basic definition. Arkin uses yet different definitions, mainly taken from biological inspirations and aptly cautions it means different things in different fields. Robin Bailey in "Introduction to AI Robotics" probably more explicitly evokes the biological origins of behavior, errors on the side of calling the meathod "reactivce", but really doesn't offer a clear definitions either.

Point is, I'd love to kow the definition from the field of endeavor to know whether I am re-inforcing the definitions, extending, or replacing them. How?

Here is this word: Behavior. No one gives a consistent definition. We might as well be talking about "thingamagiggies". No one knows what a "thingamagiggies" is, but they are quite ready to speak up, and tell you what you are doing isn't it that. Okay, their comments are one of opinion, but where is the standard against which we can test the opinion for clarity?

My whole point of starting this thread was to see if there was a solid definition for behavior as applicable to robotics and AI. If there isn't, how can it be that I'm taking something established and trying to add my own definitions.

"The problem of people redefining the same terms to mean different things is part of the reason AI keeps getting stuck. If people can't agree on the terms, they certainly cannot agree on anything else." I very much agree!

I am pointing at the interface between behavior and arbitration and saying, Look Here! Here is one of those places where the terms are really poorly defined. I think this is a very important reason AI is stuck. AI lies in the decisions that activate behavior (behavior meaning in this case primitive action behavior - because I have no better single word definitions for this version of behavior). The trigger being in the behavior part confuses use where we thing behaviors are intelligent. They might not be. It's the triggers that are doing the trick. Until we get our heads straightened out about what's behavior and what's trigger, Behavior-Based AI will remain stuck, because it isn't the behavior part that has the AI, it's a misplaced subsumption part that contains the AI.

If I may take a departure, I am reminded of the story of M. Curie. She was analyzing pitchblende and discovered beside the Uranium she was familiar with, more radiation than she could account for. So she began separating away various componds (pitchblende is a mixture of 30 some elements). Over several years of unceasing labour the Curies refined several tons of pitchblende. They progressively concentrated the radioactive components. Eventually isolating the chloride salts. In the final separation, the liquid was allowed to evaporate, and when it did, she looked into the container, and saw nothing. It appeared the radiation must have escaped, because there was nothing visible left, and yet so powerful a source of radiation couldn't come from... nothing. Where had it gone? When the lab was dark, it became clear something was left. She had extracted radium and Polonium, both new elements. There was so little of it, it was all but otherwise undetectable, but it was so powerful, it lite the darkness.

So if you will forgive me characterizing my own intentions in this thread, I am not trying to redefine Behavior Based Robotics, as you suppose. If anything I am trying to separate the components into those which have intelligence, and those which do not, because I think the part that is intelligence, is exceedingly fragile and rare, and mere traces of it have been found. Refinement is necessary to extract the essense of the intelligence, and exceeding care is necessary to find it among the grosser elements of the concoctions we now observe at large with less focused scrutiny on what is active in the intelligence, and what is not.

-- Randy M. Dumse

Things change state over time. That is all I see as a "behavior".

Some "behaviours" (changes in states) are internal and perhaps not directly observable as in a biological brain or inside a running program. All we have is part of the behavior, the bit we see at the output which may or may not be related to the other bit we can see, the input. When we see a relationship between an input we might say the behavior was triggered by the input.

When the same input can produce two or more possible outputs we have to assume different internal states. Emotions are internal states that modulate the relationship between inputs and outputs.

Intelligent behavior is behavior that we all decide is intelligent just as we decide if this is jazz, rap, country, hip hop, pop, whatever kind classification we might want to give it.

IMHO :)

-- JC

I think you're out of luck here. Intelligence is any kind of behaviour (ability to respond to environmental events) which appears to us to be purposeful, planned, but for which we're unable to discern the purpose or plan. As soon as we can discern the purpose and plan, it's just a machine and no longer thought intelligent. In other words, the word gets applied *only* to behaviours that are inscrutable. Different folk define intelligence differently because they have differing abilities to figure out how it's achieved.

You're trying to identify and discriminate what is, by common usage, inscrutable? Good luck!

Clifford Heath.

I think I hear your premise, but I have my doubts.

For instance. If we see a child reach for a pot on the stove, and getting once burned, start to do the same, then thinking better of it, I think we all conclude the child has gained some "smarts" or intelligence. We donote the purpose and the plan of reach, we denote the purpose and the plan when withdrawing at the first sense of heat the fingers to their mouth in the memory of pain.

However, don't you think the goal of AI is to reduce the unknown mechanism of Intelligence to that which is known machine like?

inscrutable \in-SKROO-tuh-buhl\, adjective: Difficult to fathom or understand; difficult to be explained or accounted for satisfactorily; obscure; incomprehensible; impenetrable.

Well, defining the unknown as the unknowable is one way of ensuring failure. The idea the Earth could in any way be round was certainly inscrutable in the early 1400's for the majority of mankind. It still is for the Flat Earth Society. I think intelligence is just another unknown.

As I hear your argument, you are saying it will always be unknown, because as parts of it become known, it will be rout machinelike, and only the unknown remaining will still be called intelligence. I can't argue against that possibility. But it is a shift in socieital norm, which is different from my intent of knowing the currently unknown. Do you see it another way?

-- Randy M. Dumse

Nonesense. I've assumed no such thing.

You asked why Jones defines a trigger as a fundamental part of a behavior "as the term is used in behavior-based robotics."

Let me repeat that last part for affect: AS THE TERM IS USED IN BEHAVIOR-BASED ROBOTICS.

Now, why do you suppose there is that caveat?

Oh, well just too hard to get a signal thru the noise.

best dpa

to observe and identify a behavior and being able to design an behavior may or may not be quite the same thing.

Would you say, if you could observe all possible inputs, and all possible output changes, you knew that you had observed all possible behaviors? (I think this question begs the question of the interface between induction and deduction, so don't trouible if you don't want to answer.)

Yes, but it is a very loose definition of state. This is the system engineers definition of state, somewhat meaning, a snap shot of all the values in the variables and settings at a given moment.

So I'm not concerned if the trigger is based on a state, such as an emotion (anger so I squint), or a current value (light to bright, so I squint). What I notice trigger is not a part of the reaction, if two different triggers cause the same reaction.

When the same input produces two different outputs depending on the timing of the input, I am very much in agreement, something has modified the reaction. Again, its not so much concern if it is state as in memory, or state as in level, but that the modification again shows, the trigger is not part of the behavior, because the behavior chosen has been modified by something else between the trigger and which behavior is output.

Sounds like we are probably in agreement here.

This is very strongly resonent with Brooks, who says, Intelligence is in the eyes of the beholder. But this is again from an observational perspective. Can we make a design, and conclude, "I don't care who you are, that there's gotta be smart." ;)

-- Randy M. Dumse

This is because people confuse "being intelligent" with being alive, conscious, sentient etc.

-- JC