Daniel Bothell

An integrated theory of the mind.

Adaptive control of thought-rational (ACT-R; J. R. Anderson & C. Lebiere, 1998) has evolved into a theory that consists of multiple modules but also explains how these modules are integrated to produce coherent cognition. The perceptual-motor modules, the goal module, and the declarative memory module are presented as examples of specialized systems in ACT-R. These modules are associated with distinct cortical regions. These modules place chunks in buffers where they can be detected by a production system that responds to patterns of information in the buffers. At any point in time, a single production rule is selected to respond to the current pattern. Subsymbolic processes serve to guide the selection of rules to fire as well as the internal operations of some modules. Much of learning involves tuning of these subsymbolic processes. A number of simple and complex empirical examples are described to illustrate how these modules function singly and in concert.

Eye Movements Do Not Reflect Retrieval Processes: Limits of the Eye-Mind Hypothesis

This research investigated whether eye movements are informative about retrieval processes. Participants learned facts about persons and locations, and the number of facts (fan) learned about each person and location was manipulated. During a subsequent recognition test, participants made more gazes to high-fan facts than to low-fan facts, and gazes to high-fan facts had a longer duration than gazes to low-fan facts. However, there was no relation between the order in which items were fixated and the relative effect of person or location fan. The effect of person and location fan on gaze duration also did not differ with whether it was the person or location being fixated. A model assuming that the process of retrieval is independent of eye movements was successfully fit to the data on the distribution of gaze durations. According to this model, the effect of fan on number of gazes and gaze duration is an artifact of the longer retrieval times for high-fan facts.

Brain regions engaged by part-and whole-task performance in a video game: A model-based test of the decomposition hypothesis

Part- and whole-task conditions were created by manipulating the presence of certain components of the Space Fortress video game. A cognitive model was created for two-part games that could be combined into a model that performed the whole game. The model generated predictions both for behavioral patterns and activation patterns in various brain regions. The activation predictions concerned both tonic activation that was constant in these regions during performance of the game and phasic activation that occurred when there was resource competition. The models predictions were confirmed about how tonic and phasic activation in different regions would vary with condition. These results support the Decomposition Hypothesis that the execution of a complex task can be decomposed into a set of information-processing components and that these components combine unchanged in different task conditions. In addition, individual differences in learning gains were predicted by individual differences in phasic activation in those regions that displayed highest tonic activity. This individual difference pattern suggests that the rate of learning of a complex skill is determined by capacity limits.

ACT-R meets fMRI

ACT-R (Adaptive Control of Thought - Rational) is a theory and computational model of human cognitive architecture. It consists of a set of modules with their own buffers, each devoted to processing a different kind of information. A production rule in the core production system can be fired based on the chunks in these buffers and then it changes the chunks in the buffer of the related modules or the state of the related modules, which may leads to fire a new production rule and so on to generate the cognitive behavior. It has successfully predicted and explained a broad range of cognitive psychological phenomena and found applications in the human-computer interface and other areas (see http://act-r.psy.cmu.edu) and may have potential applications in Web intelligence. In recent years, a series of fMRI experiments have been performed to explore the neural basis of cognitive architecture and to build a two-way bridge between the information processing model and fMRI. The patterns of the activations of brain areas corresponding to the buffers of the major modules in ACT-R were highly consistent across these experiments; and ACT-R has successfully predicted the Blood Oxygenation Level-Depend (BOLD) effect in these regions. The approach of ACT-R meets fMRI may shed light on the research of Web Intelligence (WI) meets Brain Informatics (BI).

The sequential structure of brain activation predicts skill

In an fMRI study, participants were trained to play a complex video game. They were scanned early and then again after substantial practice. While better players showed greater activation in one region (right dorsal striatum) their relative skill was better diagnosed by considering the sequential structure of whole brain activation. Using a cognitive model that played this game, we extracted a characterization of the mental states that are involved in playing a game and the statistical structure of the transitions among these states. There was a strong correspondence between this measure of sequential structure and the skill of different players. Using multi-voxel pattern analysis, it was possible to recognize, with relatively high accuracy, the cognitive states participants were in during particular scans. We used the sequential structure of these activation-recognized states to predict the skill of individual players. These findings indicate that important features about information-processing strategies can be identified from a model-based analysis of the sequential structure of brain activation.