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Modleing SGOMS in ACT-R:

Linking Macro- and Microcognition

Lee Yong Ho

Korea University

User Interface Lab

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1. Abstract

2. Introduction

3. Linking Theories

4. What makes a good linking theory?

5. SGOMS

6. SGOMS and ACT-R

7. Conclusion

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Korea University

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• West and Nagy developed and tested a method for applying GOMS to model

macrocognition. That system was called Sociotechnical GOMS (SGOMS).

• In this paper 1) we further discuss the relationship between cognitive modeling and

macrocognition and 2) describe our work on implementing the SGOMS system in

the ACT-R cognitive architecture.

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Abstract

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• The system created by West and Nagy adapted GOMS to model group work in

sociotechnical systems and is known as Sociotechnical GOMS or SGOMS.

• The relationship between microcognition and macrocognition can be understood by

analogy to the relationship between neuroscience and cognitive psychology.

• The cognitive system is a product of the neural system, most of cognitive

psychology is based on information-processing concepts that are, at best, only

vaguely related to the biological functioning of the brain.

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Introduction

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• Neuroscience results constrain and inform cognitive theories and cognitive results

help neuroscientists theorize about the functions of neural systems.

- For example, with the ACT-R architecture there have now been numerous studies trying to

link the activities of the ACT-R modules to specific brain areas and to correlate activity in

these modules with changes in blood-oxygenlevel-dependent (BOLD) reactions in functional

magnetic resonance imaging (fMRI) results. The results of these studies have provided

guidance for refining and developing ACT-R and have also contributed to the study of the

functionality of these areas.

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Introduction

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• Linking theories can be understood as theories about the relationship between

theories or findings that exist at different levels.

• Importantly, linking theories can provide insights and new directions for either of

the two theories being linked. This has certainly been the case with the work

linking ACT-R and neural localization.

• Of course, those results are, ultimately, produced by neurons, but the results were

obtained by experimenting and theorizing at the cognitive level, and it seems clear

that they would have been extremely difficult to discover using the methods of

neuroscience alone.

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Linking Theories

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• Therefore, other ways of modeling this in ACT-R would be considered competing

theories, as would alternative models created with systems other than ACT-R.

• This type of approach is important for two reasons.

- First it makes the linkages between micro- and macrocognition clear.

- Second, to test this type of linking theory, it would be necessary to show that it can account

for a specific type of macrocognitive activity across a wide range of tasks.

The linking theory should function as a guide or a template for how to use the

architecture to produce the macrocognitive activity in models of different tasks.

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What makes a good linking theory?

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• GOMS is a cognitive architecture that stands for Goals, Operators, Methods, and

Selection Rules.

• SGOMS is a linking theory that links GOMS with the macrolevel S theory.

• The S theory is about how people maintain a hierarchical model of routine tasks

while dealing with interruptions, multitasking, and replanning.

• SGOMS links S to GOMS through three mechanisms.

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SGOMS

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• The first is through the unit task concept.

• Within GOMS, the unit task is a control structure with the purpose of minimizing

overloads and delays.

- Overload occurs if information arrives from the environment too fast for the human to adequately

process it or if the system requires the human to respond faster than is possible.

- Delays occur if information arrives from the environment too slowly.

• SGOMS adds interruptions as a third factor defining unit tasks. If a unit task is too

long it is likely to be interrupted, which is similar to being overloaded in that the

unit task cannot be completed. Therefore, in SGOMS, unit tasks represent islands

where no interruption is expected or likely.

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SGOMS

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• The second mechanism is the planning unit.

• Planning units are also control structures, but they are used to prevent individuals

from acting at odds with their group or with the environment.

• A planning unit is a sequence of unit tasks for accomplishing a specific goal.

• The third mechanism is a cycle of operations that describes how the planning units

and unit tasks fit into the overall work picture (see Figure 1).

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SGOMS

Figure 1. The SGOMS framework

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• GOMS models can stand on their own, but they are often implemented in ACT-R.

ACT-R contains all of the cognitive elements required by GOMS, so this entails

using ACT-R to build the model in a way that is consistent with GOMS.

• There are several places in the SGOMS model where a GOMS approach is

problematic (see Figure 1).

• SGOMS approach is satisfactory as a practical methodology that can be easily

applied. By using ACT-R we hope to fill in the black boxes, but this comes at the

cost of a much more complicated model. Therefore, at this point we regard the

ACT-R model as a research tool and not as a practical methodology

The goal of this is to gain insight into the two theories that are linked: the ACT-R

architecture and the macro part of the SGOMS theory.

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SGOMS and ACT-R

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1. Planning Units and Unit Tasks

• In ACT-R, behaviors can be driven directly by the procedural memory module or

indirectly through the declarative memory module acting through procedural

memory.

• Eventually, the more direct productions take over because of the reward-based

learning system in the procedural memory system that factors in time costs for

completing a task. Because the more direct productions are faster, they eventually

become preferred.

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SGOMS and ACT-R

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• This theory has some implications for how SGOMS can be understood. In SGOMS,

unit tasks are considered to be sequences of actions that can usually be completed

without interruption.

• Therefore, for experienced workers we would expect well-learned routines within

unit tasks to be mainly executed by productions.

• However, recalling something from declarative memory might still occur. Any

aspect of the task that changes across time would fail to become entrenched as a

production because when it changes the compiled production would contain

incorrect information, leading to a failure and a punishment instead of a reward.

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SGOMS and ACT-R

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2. Parallel Monitoring

• SGOMS assumes that the environment is monitored in parallel with doing the task .

ACT-R has perceptual modules that operate in parallel with the procedural memory

module (see Figure 1).

3. Interruption

• If the utility of this production is set lower than the utilities of the other

productions, it will be able to fire only if none of the other productions match.

• However, interruptions are more difficult to handle when information that should

cause an interruption is placed in a buffer but does not prevent the firing of the

normally expected production.

• In SGOMS, unit tasks represent islands where no interruption is expected or likely.

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SGOMS and ACT-R

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4. Evaluation and Patch

• In SGOMS, the situation is considered OK if no problem is detected. If there is a

problem, there is a request to declarative memory to determine whether this is a

problem with a solution (see Figure 1).

• If there is a solution, then it is implemented and the evaluation is done again. If

there is not a solution, the “choose planning unit” box is evoked.

• This is fairly straightforward in ACT-R.

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SGOMS and ACT-R

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5. Choose Planning Unit

• Our approach to modeling this is to use heuristics.

• An interesting prediction that flows from this is that the order in which planning

units are considered will be determined by how frequently they are performed,

because the ones that are performed more often will have a higher activation level

and will be more likely to be chosen first.

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SGOMS and ACT-R

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• Using a microcognition based architecture such as ACT-R to build macrocognitive

models is a way of creating linking theories: specific theories about the relationship

between the microcognition-based architecture and classes of macro level

behaviors.

• We noted the need for such theories to be tested across a wide variety of tasks.

• In terms of our SGOMS/ACT-R model, the next step is to build it and test it.

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Conclusion