zaterdag 3 juni 2017

Some Thoughts on the Cognitive Agent

I will use this post to try and structure my incoherent thoughts about the structure of cognitive agents.

The Theater

At the heart of the cognitive agent should be a theater, as proposed by Bernard J. Baars in his Global Workspace Theory. The theater represents human working memory, conscious activity (the spotlight on the stage) working serially, and the many unconscious processes working in parallel.

In this theater, decisions are made. Tasks are selected. It is a Task Manager.


The agent has needs. These are hard-coded like the need to help the user fulfill its goals or the need for self preservation. These needs define the soul of the agent. 

The idea of needs is from Maslow, designed for humans, but can be applied to other agents too, as this image illustrates:

The need of helping the user looks like this:
The number of unresolved user requests should be 0.
Importance: 0.8
The needs of an agent drive it. They determine what goals it will create and their relative importance.

"Needs" may alternatively be called "drives" or "concerns".


Needs lead to goals, based on input. If the user asks a question, for example, this will be interpreted as a user request:
User Request: "Is there a restaurant here?"
Urgency: 0.2
If the user makes a command, it will be treated the same way:
User Request: "Send me an e-mail if anyone mentions my website"
Urgency: 0.1
The question named here is a request that may be answered immediately. The command, however, becomes a permanent request.

The agent does not execute the user's request just because it's there. Executing the request just becomes a goal because one of the agent needs is to fulfill the requests of its user.

The agent has sensors that notice that its needs change. These sensors create active goals (instantiated from a template, its variables bound). These goals are entered into the Task Manager.


In order to reach a goal, the agent needs to follow a plan. In the restaurant example, the agent may have a plan like this. It consists of these steps.

  • Find current location (L)
  • Find user food preference (P)
  • Find restaurants of type P within distance D of L
  • Present the restaurants to the user

The plan is instantiated and handed over with the goal to the Theater. Note: no task is treated as something that may be executed immediately, synchronously. Every task needs to go through the theater.

Note that all cognitive activity takes the form of plans and tasks. Yes, that includes all deduction tasks. It presumes a Datalog type of knowledge representation, a logical form that is procedural in nature.
goal :- location(L), preference(P), restaurants(P, L, R), show(R).

Theater: Task Selection

The Theater, as a Task Manager, keeps track of all active plans. Each active plan has an active task.
At any point multiple active tasks may "scream for attention".

Now, the system as a whole may do many things simultaneously. But the thing is, each of its modules can only do one thing at a time. So when a given module is busy, it cannot handle another task at that time.

The Task Manager knows which modules are active and which ones are idle.

All active tasks scream with a loudness of:
Priority = Importance * Urgency
The task with the highest priority is selected by the Task Manager. This task is placed in the spotlight. TM asks all idle system modules to handle the task. The first one gets it. Or the one that bids most (as in an auction).

The Task Manager hands the task over to the module, and places it on the waiting list. TM will receive a "done" event from the module later, at which point it binds the result values to the active plan and advances the active plan to the next task. When all tasks are done, the active plan is removed.

Dialog Manager

The task "find user preference for restaurant" may have two implementations:
  • find preference in user database
  • ask user for preference
If the first task fails, because the preference has not been asked before, the second task will be performed. It is performed by the Dialog Manager. The DM is "just another module" of the system.

As soon as the "ask user for preference" task enters the Dialog Manager, it becomes active, and will remain active until it has received a reply from the user. This way, the system will not ask several questions at once.

Likewise, if the user has just asked something, DM will start active mode, and will first reply to the user before starting a question of its own.

The Dialog Manager may also initiate conversation on its own, based on a dialog plan. It cannot just start by itself, however. It needs to send a goal and a plan to the Task Manager, and request attention.

Episodic Memory

All active goals, plans and tasks are logged in episodic memory by the Task Manager. Or EM simply listens to TM. Storage occurs in a structured way. For every task, it is possible to retrieve its plan, its goal, and, ultimately, its need.

The reason for this is that Episodic Memory thus becomes a knowledge source for auditing. It allow the user to ask the question: "Why did you do that?"

This is also an important reason why all tasks need to go through the Task Manager. This way all activated tasks are accounted for in a central place.


Remember the sensors that register that needs change? They can start emotions too. To do that, they use two types of parameters:
  • digression from the norm
  • time left to deadline
The norm in the example of assisting the user is 0 requests. If the number of requests becomes larger, like 5 or so, the need to assist the user becomes strained. In order to correct it, the importance of the need is temporarily increased. Remember the "importance" of a need? This is not a fixed value; it has a base value and increases as the need is strained.

If this does not sound very emotional, that's because it it just the arousal aspect of emotion. It causes one to become more excited in a certain area. Arousal is involuntary, it does not need to go through the theater to become active.

It is also possible to give the agent emotional expressions. It may start yelling to hurry up or to shut the pod bay doors. These expressions become (very) conscious and need to pass through the Theater in order to become active.

I suggest reading The Cognitive Structure of Emotions if you want to know more.

In Closing

I made some progress. Things are starting to make sense.

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