The items in brackets are variables with ranges. Once some of the variables have been set, the agent can infer the values of some of the others (or at least possible values). For example, if
is known to be greater than $1 million, then the agent might infer that the list of buyers could include people like Bill Gates, but not Bob Marinier. Not all elements in a schema are necessarily variablized; some may be concrete values that are inherent to the concept. Our comprehension system is built on event schemas [Zacks and Tversky, 2001]. The reason for focusing on events is that situations seem to be composed of series of events [Zacks and Tversky, 2001], and it is the understanding of these events that let an agent choose actions to initiate its own events. Others have also focused on events as the primary stimulus (e.g. Ortony et al. [1988]). Let’s consider an example. Suppose an agent has a schema for the “crossing the street” event: Schema: Crossing the street Event1: Step down from curb Event2: Walk across street Event3: Step up onto curb Thus, the abstract event “crossing the street” is defined in terms of more concrete events. These may also be broken down further. At some point, however, an abstract event will be composed of ground events which are the most basic units. These ground events are the events the agent recognizes when it encodes raw inputs. They also correspond to actions that the agent can directly execute in the world. For simplicity, we have not shown the explicit figures, motions, etc., which would typically be variablized, in this example. Now suppose the agent observes someone stepping down from a curb. It can now recognize that this is the first step of the “crossing the street” schema. If it commits to this interpretation, it can make predictions about what will happen next (e.g. that the person will walk across the street and step up onto the other curb). Comprehend Event
Determine Discrepancy from Expectation
Determine Goal/Need Conduciveness
Update Interpretation
Reinterpret events
Figure 2: The event comprehension process
It can also infer something about the other agent’s goals (e.g. that it wants to cross the street). Perhaps most importantly, the agent can infer what the meaning of this event is with respect to its own goals – is it ok for me if this person crosses the street? When the next event occurs, this may confirm the predictions or the agent may have to reinterpret using some other event schema. The initial choice of event schema may be impacted by several factors; for example, if the agent wants the person to cross the street, then it may be biased to interpret the initial event that way.
3.4
Th e Co mpre hension Pro cess
The comprehension process creates and maintains event schemas which represent the agent’s understanding of what is currently going on. Suppose that an agent already has a schema it has committed to based on prior processing. It perceives and encodes an event and then attends to it. Since it is an event, the agent executes a “comprehend event” operator. This operator breaks down into two steps: determine the discrepancy from expectation, and update the current interpretation (i.e. the event schema). Determining the discrepancy from expectation is necessary in order to decide how the interpretation should be updated. For example, if the event exactly matches the agent’s prediction, updating the interpretation may just be a matter of denoting that event has occurred. On the other hand, if the event is slightly different (i.e. of the same type but with different variable bindings), then the event may need to be swapped in for the prediction, and the future predictions updated to reflect the latest information. Finally, if the event is completely different than what was expected, the current interpretation may need to be entirely replaced with a reinterpretation that is consistent with its observations. This is the first example of how some appraisals may “fall out” of the agent’s processing. The “determine discrepancy from expectation” operator is an appraisal from Scherer’s [2001] theory, but similar ones exist in other appraisal theories. Figure 2 shows the comprehension aspects of the PEACTIDM process. As depicted, once the agent has comprehended the event, it can generate another appraisal, “goal/need conduciveness.” This appraisal is different in that it does not “fall out” of the comprehension process, but rather follows it. Since it isn’t required to comprehend, the agent may only generate it if it has enough resources to do so (e.g. time). In general, we can divide appraisals into at least 3 groups: 1) automatic appraisals (e.g. novelty may be computed automatically by the high-level vision or long-term memory systems), 2) deliberate but required appraisals (i.e. those appraisals which “fall out” of the comprehension process), and 3) deliberate but optional appraisals (i.e. those which the agent may do if it has time). This is not to imply that the agent can choose not to do optional appraisals. Rather, continued comprehension may take precedence over these appraisals, so they may be skipped if events are occurring rapidly. Table 1 shows some possible appraisals and what types they might have.
Table 1: Possible types for common appraisals. Appraisal Type Appraisal Automatic Novelty Intrinsic pleasantness Causality Deliberate-required Goal/Need relevance Discrepancy from expectation Outcome probability Deliberate-optional Goal/need conduciveness Coping potential These particular appraisals are merely exemplars. Rather than take a firm stance on the exact set of appraisals at this point in our research, we view the comprehension process as providing constraints on what the set of appraisals should include. That is, some appraisals may fit more naturally than others into the comprehension process. Of course, the constraint goes both ways in that the comprehension process must allow for many common appraisals. Novelty and intrinsic pleasantness are likely properties that arise during the encoding process, which is mostly automatic. The agent may get causality automatically when it chooses a schema. That is, the schema itself may include the causality information in its structure. That is not to say that determining causality in general is not a complex process that is not automatic; presumably the agent must sometimes go through that process when it is generating a new schema to understand a novel set of events. The distinction between required and optional deliberate appraisals may lie primarily in what is required to understand what is happening in order to act immediately vs. what is required to understand the relationship of what is happening to the agent’s goals. This distinction is slightly muddled because the agent’s interpretation is colored by its goals. Thus, we consider goal/need relevance to be required; it may occur as part of the attend process (i.e. the agent may ignore events irrelevant to its goals). Goal/need conduciveness and coping potential, on the other hand, do not seem to be critical to the immediate understanding of what is happening, but clearly it is in the agent’s interest to do these if it can.
3.5
Prop ertie s revi sit ed
Does the comprehension process fulfill each of the requirements described earlier? •
• •
Domain independent: The system works on events, which are a domain-independent representation of what is happening. There can be domain-dependent knowledge used in comprehension, but the basic process can be used in any situation. Limited working memory: The system only represents one interpretation at a time. Incremental: The system can attend to and process one event at a time,
•
• • •
•
•
Happens over time: Since events occur over time, the agent processes them over time. The delay between events is actually necessary in order for the agent to complete its processing without becoming overwhelmed. The agent may be able to utilize any extra time it has to generate additional appraisals. Immediate comprehension: The agent commits to an interpretation starting with the first event. Supports hierarchical comprehension: The event schemas describe events at multiple levels, directly supporting hierarchical comprehension. Supports prediction: The hierarchical nature of comprehension and event schemas directly support prediction. Once a high-level schema has been recognized, the subsequent events that it contains are predictions. Immediate ambiguity resolution: If multiple interpretations are available, the agent will pick one; possible methods include the one that best fits its goal, its prediction, or its current emotional state. Error recovery: There are at least two levels of error recovery: a simple level, in which the schema structures are correct but the variable bindings need to be updated, and a complex level in which the structure itself is incorrect and the agent needs to choose a new schema. The simple level may be implemented via a truth maintenance system that automatically updates the variable bindings used in the next predicted event. The complex level may utilize arbitrary processing. For example, the agent can recall the most recent event sequence from episodic memory and try to find a schema that matches that set.
The properties that we have described thus far are properties of the comprehension process itself, regardless of its realization. However, since the comprehension process is embedded in a cognitive architecture, we get the additional property that the process is impacted by emotion (and other processes) via the impact of those processes on the cognitive architecture. For example, research indicates that one’s emotional state can impact memory retrievals [Forgas, 1999]. Thus, those aspects of the comprehension process that are impacted by memory (i.e. nearly every step) are also impacted by emotional state.
3.6
Fe eling , co mpreh ensi on, and co ping
Although we traditionally think of the external world as being the total environment in which the agent must behave, for the cognitive system, the environment also includes internal perceptions such as feelings [Frijda, 2005]. Feelings serve as feedback about the meanings derived via the comprehension process. Just like external events, these “internal events” are processed through PEACTIDM – that is, they must be perceived, attended to, and comprehended. It is by understanding its feelings that the agent can put its action urges in context and actually Intend them, as opposed to simply
reacting [Frijda, 2005]. This also allows the agent to generate novel responses to its feelings, such as when it tries to cope. Finally, it allows for the possibility of metaemotions, or emotions about one’s feelings (e.g. shame at feeling fear) [Lambie and Marcel, 2002].
4
Predictions
This theory entails a number of predictions. First, because the comprehension process results in immediate comprehension, if the agent’s perception of a stream of events is interrupted, the agent should have an understanding of the situation up to that point (which will often include predictions as to what might happen next and what other agents are trying to do). Thus, an interrupted agent will behave based on the information received so far, but that behavior may be flawed in predictable ways due to mistakes in the agent’s interpretation (similar to garden path phenomena in language processing). Furthermore, the comprehension process imposes a partial ordering constraint on appraisal generation. For example, as shown in Figure 2, the “Discrepancy from Expectation” appraisal occurs before the “Goal/Need Conduciveness” appraisal. This is consistent with Scherer’s [2001] theory which also hypothesizes a sequential ordering. However, the reasons for the hypotheses differ. Scherer’s reasoning is that it would be a waste of processing resources to do some appraisals when the results of others show that they are irrelevant. For example, “Discrepancy from Expectation” comes after “Goal Relevance,” because if an event is not relevant, then the agent should ignore it. By contrast, our theory imposes an ordering because of the functional requirements of the comprehension process. A corollary of this is that our model allows for the possibility that different emotions will inherently require different amounts of processing. If some emotions only require appraisals that occur earlier in the comprehension process, then those emotions will take less processing than those that require more appraisals. The idea that different emotions may require different amounts of “cognitive activity” is not new [Lazarus 1982]. The differences in processing requirements may in turn lead to timing effects. Other theories propose that some basic emotions are refined into more complex emotions [Ortony et al, 1988; Weiner, 1986], which is compatible with our theory. Given that comprehension takes time, if time constraints are tight, some appraisals may not get generated, meaning that under certain time pressures, some emotions may not occur, or may be based on appraisals that were generated in earlier situations. Under extreme time constraints, comprehension itself may not be possible, leading to purely reactive behavior. In between, it may be possible that an agent “misses” some of the events, leading to flawed interpretations. Our model also supports appraisals that can happen at different time scales. Some appraisals may be based on comprehension in novel circumstances that require multiple retrievals from long-term memory, or even significant internal problem solving to understand the
situation, while others could be based on comprehension in well practiced situations where essentially reactive comprehension is possible. These differences in comprehension processing can lead to very different time scales for generating appraisals. Combining this with the previous two points, we predict that the complete appraisal (and thus the emotional reaction) can change over time as the comprehension of the situation evolves over time, which is also consistent with other theories (e.g. Ortony et al. [1988] and Weiner [1986]). Finally, we can also make a prediction regarding the coping process. Since Intending only occurs as part of problem-focused coping, and since Intending is the only route to deliberate action, one expected outcome is that if someone engages in emotion-focused coping first (e.g. to form a new goal), then there should be an extra delay before the agent’s next action. This is hardly surprising since the agent essentially needs to do a task switch internally before it can proceed. However, our model shows explicitly why and how the delay is incurred, which may lead to empirical predictions regarding the timing of this in humans.
5
Conclusion
In conclusion, a comprehensive model of emotion based on appraisal theory needs a detailed theory about how appraisals are generated. Our hypothesis is that comprehension plays a central role in generating many appraisals. Furthermore, by theorizing about appraisals in the context of comprehension and vice versa, we impose important constraints on our theories which help guide us to plausible solutions. Finally, comprehension may provide the framework in which the agent does all of its processing, including postappraisal functions like coping. The next steps for our own research are to create and evaluate a complete computational model of the above theory of comprehension, as well as the other components of our theory of emotion as shown in Figure 1. By doing this, we will gain a greater understanding of how comprehension (and thus appraisal generation and coping) integrates with and guides the agent’s general processing and also develop new criteria for determining which appraisals are appropriate for emotion theory (i.e. which ones fit into the comprehension process). Finally, we will produce specific testable predictions that can be used to help guide future research in emotion theory.
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