Goal-Based Pedagogical Agents
Federal Armed Forces University Munich
85577 Neubiberg, Germany
This paper proposes goal-based agents attached to networked applications and learning environments to support user's work and learning. Users, learners, applications and learning environments are represented by autonomous goal-based social agents which communicate, cooperate, and compete in a multi-system and multi-user distributed environment This approach allows to consider in a uniform way working, adaptation to the user's goals and preferences, level of experience and available resources, as well as teaching the user using various teaching paradigms (consrtuctivist or instructivist). In addition it allows taking into account of userís /learnerís motivation and affect; as well as a coherent discussion of teaching strategies.
1 Trends in the Development of Adaptive and Teaching Systems
Two major trends can be observed in the development of learning environments which follow from the rapid development of the networking and communication technologies:
An integration of working and learning environments.
Nowadays nearly all commercial applications (most prominently CorelDraw, Toolbook etc.) are equipped with training programs, which provide an introduction into the main features and basic working techniques, as well as with on-line help which is in some cases context-sensitive, and even adaptive (MS-Office 97). This means that the user is working and learning in the same time, he can switch from "working"-mode to "learning"-mode to get some information, CAI-type of teaching, or demonstration which will help him learn about something specific needed at the moment and then switch back to the "working" mode to try and use the newly acquired knowledge in practice.
From the other side, learning environments specifically designed for educational purpose in some subject tend to be inspired by constructivist and Vygodskian theories of learning, which focus on context-anchored learning and instruction, which takes place in the context of solving a realistic problem. There is a tendency in learning environment design philosophies towards integrating work with learning; work being the source of problems and motivation for learning.
In general, one can observe a convergence between working (sometimes also adaptive) environments and learning environments. For example, instead of adapting to sub-optimal learner behavior, the system may decide to teach the learner (instruct, explain, provide help, etc.) how to do things correctly, i.e. to make him adapt to the system by learning. In reality every adaptation is bi-directional (there is a physical law that every action has an equal counteraction). Every participant in an interaction process adapts to the other participant(s). The system learns about the user and adapts to him/her; the user learns about the system and adapts his behavior accordingly. An adaptive system should support the userís learning of the system (Vassileva, 1996). It has to be able to decide whether to adapt to the user at all or is it better to teach him something instead (i.e. to make the user adapt to the system), i.e. whether to be reactive or proactive. In this way the system will be an active participant in the interaction, an autonomous agent, which can decide in the course of interaction and not just follow embedded decisions made at design time (normative decisions).
An attempt to build such a system which can take decisions about whether to teach or to coach the student depending on the context of interaction and state of student model has been designed and implemented using reactive planning techniques (Vassileva, 1995). However, we feel that such a pedagogically "competent" system has to be able to negotiate its decisions with the learner and not just impose them on him, since whatever expertise is underlying these decisions, there is always uncertainty about the correctness of this knowledge and about the student model.
Therefore we decided to model the pedagogical component in a intelligent learning environment as an autonomous agent which pursues certain own goals (teaching goals), which can be cognitive (subject- and problem-specific), motivational, affective (learner- and subject-specific). We call these agents "Application agents", since they are associated with an application which can be in a special case, a learning environment. Since the user / learner is also an autonomous agent pursuing his / her own goals, the decision of which and whose goals will be pursued (the pedagogical agent's or the learner') is made interactively, in a process of negotiation and persuasion.
In pursuing its goals, an application agent uses explicitly its relationship with the user/ learner. It can modify the parameters of the relationship, so that it can adopt user goals or learner goals and provide resources for them (achieving in this way a microworld-types of explorative learning), infer and adapt to the learner's goals (to provide adaptive help or coaching) or try to make the learner achieve the teaching goals of the agent (to instruct the user / learner how to do something).
No Virtual Difference between Humans and Application Agents.
It is no longer necessary that the teaching system is a almighty teacher knowing the answer to any question that may arise in the learner during the interaction /learning session. Networking provides a possibility to find somewhere else a system or a human- partner who can help the learner with his/her problem and explain him/her something which the system itself has no resources to do. This trend can be seen in the increasing work on collaborative learning systems, which are able to find appropriate partners for help or collaboration, to form teams and support goal-based group activities (Hoppe, 1995), (Collins et al, 1997). For this purpose, it is needed that teaching systems (also computer applications providing adaptive help) are able to communicate the information about their users (user models), about their available resources and goals, in order to find an appropriate partner. We can imagine application agents, attached to every application or learning environment, which have an explicit representation of the user's or applications goals, plans, resources. These agents communicate and negotiate among themselves for achieving their goals. This means that we need an appropriate communication language about goals and resources which would allow these agents to share information. This communication has to be on a higher level than the level of knowledge communication KQML or KIF, since it has a different purpose: while KQML and KIF have to define how exactly the agents communicate their knowledge, this higher level of communication has the purpose to define who will be contacted, about what, when and how it will take place (i.e. in which direction etc.). This level of communication has to be also transparent for humans, since some of the partners may be human-agents.
2 Goal-Based Agents
We propose creating "application agents" associated with applications, tutors, coaches and learning environments (see Figure 1). These agents will possess an explicit representation of the goals for which the application has resources and plans. Usually, these goals are embedded implicitly in the application at design time and can be achievement goals (for example, creating a table in Word), typical user tasks (which the application supports), and user preferences (normally also embedded at design time). Teaching applications have normative teaching goals (i.e. what the application is supposed to teach), which can be further classified into content goals, presentation goals and tasks, psycho-motoric and affective (motivational). Every application is provided at design time with resources and plans for achieving these goals (data, knowledge, functions of the application).
Human agents also possess goals, resources and plans. Classifications of human goals have been proposed by Schank & Abelson (1977) and later by Slade (1994). Slade proposes also various dimensions for goals, like polarity, persistence, frequency, deadline etc., which influence the goal-importance. Human resources can be divided into two categories: tangible (money, time, objects, skills, credentials, rank etc.) and cognitive (memory, attention, knowledge, affects, moods). The resources can be classified with respect to whether they are perishable, expendable, interchangable, transferable etc.
Humans communicate their goals, available resources and plans to their "personal agents", which serve as mediators in search for other application- or personal-agents that can provide resources and plans for achieving the goals of the human users. In this way, a human user and a software application appear in a symmetric position, they posses goals, resources and plans, and they can adopt each other goals (i.e. help each other achieve their goals) mediated by the "pedagogical agents" and the "personal agents" (see Figure 1.)
Figure 1. Personal and Application Agents
A Goal-Theory of Agents
According to Slade's (1994) theory of goals, the behavior of a goal-based agent (for example, humans) follows the principle of importance:
Principle of Importance The importance of a goal is proportional to the resources that the agent is willing to spend in pursuing this goal.
In order to infer each other's goals, the agents use several clues: the principle of investment, the affects and the "moods" of other agents.
Principle of Investment The importance of an active goal is proportional to the resources that the agent has already expended in pursuit of that goal.
Motivation An agentís motivation to pursue a given goal is equivalent to the importance of the goal for the agent. So, the motivation of a human to pursue a given goal is proportional to the resources that the agent is willing to spend in pursuing this goal.
Humans possess not only tangible resources, like money, time, hardware configuration, etc., but also cognitive resources, like attention, memory, affect, moods etc.
Attention is the amount of processing time spent by the agent in pursuing some goal.
The following corollaries of the principle of importance can be formulated:
The importance of a goal is proportional to the attention / amount of processing time which the agent is willing to expend in pursuit of that goal.
The importance of a goal is proportional to the degree of affective response to the status of that goal.
This means that the difference among happiness, joy and ecstasy relates to the importance of the goal that is achieved or anticipated. Happiness does not depend only on the world, but also on oneís idiosyncratic goal hierarchy. Knowing the humanís emotion (via an appropriately designed interface e.g. buttons allowing the user to directly communicate his / her emotion), the personal agent can infer the importance of the goal, on which the user has just failed or succeeded. Knowing the importance of the userís goal, the system can predict his affective response to goal-achievement or -failure.
Goal persistence is reflected in persistent affective states, or "moods". The intensity of the mood reflects the importance of the related goals. An agent is in a good mood when he has achieved an important persistent goal. According to the principle of importance, the agent has prepared to expend considerable resources to achieve this goals. Now these resources are free for other goals. So an agent in a good mood effectively has excess resources that could be used for new goals. An agent in bad mood has lack of resources, so will be much less open to pursuit any new goals. This fits to our everyday experience. There is a heuristic that suggests that you get someone in a good mood before delivering bad news or making a request. This can be used in order to decide whether a system should teach the user (i.e. make him/her adopt the system's teaching goal) or whether it should adapt to the user (i.e. the system adopts the user's goal).
An agent must act in a world populated by other agents: many of a agentís goals require the help of another agent. In this way, relationships among agents can be viewed as another kind of resources for achieving goals.
Principle of Interpersonal Goals Adopted goals are processed uniformly as individual goals, with a priority determined by the importance and context of the relationship. Thus the particular relationship determines both what goals will be adopted in what context, and what importance will be assigned to those goals. The principle of importance applies to adopted goals, meaning that a person will expend resources in pursuit of an adopted goal in proportion to the importance of this adopted goal. The same applies to cognitive resources. For example, the agent will spend more attention (time thinking) about the interests or problems of a close friend than those of an acquaintance.
Parameters of Relationships: Inter-agent relationships can be characterized by the following parameters:
1) Type of the other agent involved in the relation:
2) Type of Goal Adoption
3) Symmetry of Relationship
4) Sign of Relationship
Positive <[ ---------------[-----------------------]------------------] > Negative
collaboration cooperation competition adverse
The importance and the context of the particular relationship for a given agent determines both what goals will be adopted by the agent, and what importance will be assigned to these goals. The principle of importance applies to adopted goals, meaning that a person will expend resources in pursuit of an adopted goal in proportion to the importance of the adopted goal. The same applies to cognitive resources. For example, the agent will spend more attention (time thinking) about the interests or problems of a close friend than those of an acquaintance.
If an agent A wants that another agent B adopts A's goal as an important goal, it uses persuasion strategies. These are inter-agent planning strategies which aim at increasing the relative goal importance for another agent of an adopted goal. Persuasion strategies may, for example, exploit the importance of the relationship between A and B ("if you don't do this, I won't play with you anymore"), they can increase the importance of the goal B by bargaining resources, or offering that A will achieving a goal of B in exchange ("if you do this for me, I will do that for you"). A set of persuasion strategies was proposed by Schank & Abelson (1977). Persuasion strategies are particularly important when the type of goal adoption is "Goal Development", i.e. when agent A has a teaching goal and it wants that agent B adopts this goal as an important goal (thus B will be motivated to achieve the goal, i.e. to learn). We can consider some teaching strategies used by human teachers as a special case of persuasion strategies aimed at motivating the student to achieve some teaching goal. One can easily find parallels between the conditions for successful persuasion formulated by Slade (1994) and some conditions for successful teaching. Slade's conditions are the following:
For example, the first condition states that the student has to know exactly what is the goal he /she is trying to achieve. The second condition states that the student has to have the necessary prerequisite knowledge and cognitive resources free at the moment in order to be able to pursue a given teaching goal.
Another important characteristic of a relationship is its closeness. The closeness of relationship denotes how well the agents understand (are aware of ) each otherís goals. When talking about closeness, we always mean closeness from the point of view of a certain agent: it can well be the case that one agent understands the goals of the other one well, but the second one is not aware of the goals of the first one. Agents learn about each otherís goals from three main sources:
The closeness of the relationship between a human user and his / her personal agent should be as high as possible. This means that a personal agent must use not only normative and directly communicated knowledge about the user's goals, but should be able to infer user goals from his /her behavior (methods for diagnosis in user modeling and plan recognition could be applied), but also from the user's affects and moods (communicated in some way from the user to his /her personal agent).
An agent which is able to represent explicitly, reason about and modify the parameters of its relationships with other agents, when it is able to create and destroy relationships according to its goals, is called a social autonomous goal-driven agent.
Personal agents and application agents (which can be pedagogical agents if the application is a learning environment) are examples of social autonomous goal-driven agents.
A personal agent can be related with the human user with an asymmetric goal-assignment type of relationship (i.e. the application receives and executes commands from the user). In this case, the personal agent searches among the available relationships with application agents the one which is most appropriate for achieving the current user's goal. If no such relationships are available, it will contact a broker-agent which has a large amount of relationships to various application agents (including pedagogical agents). It will find and contact an application agent which can fulfill the goal. The personal agent will negotiate with the application agent (see Figure 1) in order to find reasonable for both sides conditions for obtaining the service. When agreement is found, the application agent adopts the user goal and provides its normative resources and plans for achieving the user's goal.
Pedagogical agents have a set of normative teaching goals and plans for achieving these goals as well as persuasion plans (i.e. teaching strategies) and associated resources in the learning environment. The persuasion plans can involve a modification of the parameters of the relationship between the pedagogical agent and the user. For example, it can change the sign of the relationship from collaborative to adverse (game-like) or to cooperative (simulating a peer-learner), or the symmetry of the relationship from user-dominated (a constructivist type of learning environment), to symmetric (coach), or pedagogical agent dominated (insturctivist tutor).
If a personal agent is able to reason about the relationship with the user and modify it, it can decide not only to fulfil the user's orders, but to change the relationship to a symmetric goal-development type, or to take the initiative in its hands and teach the user something suggested by the corresponding application agent. For this to happen, the personal agent should have adopted a goal from a pedagogical agent of some learning environment (who has managed to persuade the personal agent that it is in possession of resources and plans for pursuing a teaching goal related to the current goal of the user). In this case, the personal agent has to make a decision between two conflicting goals (the achievement goal of the user and the adopted teaching goal from the pedagogical agent of the learning environment). In order to be able to make decisions, the personal agent needs to be able to reason about the relative importance of the goals and to plan resources.
3 An Architecture for Autonomous Goal-Based Social Agent
Ideally, an autonomous cognitive agent will possess a reactive, reasoning, decision-making and learning capability. Therefore it has to contain processes implementing these capabilities. We propose an architecture for an autonomous goal-based social agent (see Figure 2) which contains the following components:
Figure 2. An Architecture of Intelligent Personal /Application Agent.
A personal agent with this architecture should have the following properties
An agent defined in this way fulfils Nwana's (1996) definition for "smart" agent and is an ideal, to which one could strive. However, to bring this architecture to a computational framework, one has to find new techniques for reasoning and decision-making about inter-agent relationships. We are currently working on the implementation of a first version of social agents who can communicate among themselves in terms of goals and resources. To this we intend to add gradually capabilities of reasoning about goals, inferring of goal importance of other agents, decision making and inter-agent planning (persuasion).
Hoppe H.U. (1995) The use of multiple student modeling to parameterize group learning. In Artificial Intelligence and Education: Proceedings of AI-ED 95, AACE, 234-241.
Collins J., Greer J., Kumar, V., McCalla, G., Meagher P., Tkatch, R. (1997) Inspectable User Models for Just-In-Time Workplace Training, in User Modeling Proceedings of UM97, Springer Wien NewYork, 327-338.
Nwana H. (1996) Software Agents: An Overview, Knowledge Engineering Review, 11, 3, 1-40.
Schank, R. and Abelson, R. (1977) Scripts, Plans, Goals and Understanding. Lawrence Erlbaum Assoc., Hillsdale, NJ.
Slade, S. (1994) Goal-Based Decision Making: An Interpersonal Model. Lawrence Erlbaum Associates Inc. Hillsdale, NJ.
Vassileva J. (1995) Reactive Instructional Planning to Support Interacting Teaching Strategies, in Proceedings of the 7-th World Conference on AI and Education, 334-342, AACE: Charlottesville, VA.
Vassileva, J. (1996) A task-centered approach for user modeling in a hypermedia office documentation system, User Modeling and User Adapted Interaction, 6, (2-3), 185-223.