Spanning seven orders of magnitude: a challenge for

There has been a proliferation of proposed mental modules in an attempt to account for different cognitive functions but so far there has been no successful account of their integration. ACT-R (Anderson & Lebiere, 1998) has evolved into a theory that consists of multiple modules but also explains how they 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. Empirical examples are presented that illustrate the predictions of ACT-R’s modules. In addition, two models of complex tasks are described to illustrate how these modules result in strong predictions when they are brought together. One of these models is concerned with complex patterns of behavioral data in a dynamic task and the other is concerned with fMRI data obtained in a study of symbol manipulation.

We describe a computational model of how analogs are retrieved from memory using simultaneous satisfaction of a set of semantic, structural, and pragmatic constraints. The model is based on psychological evidence suggesting that human memory retrieval tends to favor analogs that have several kinds of correspondences with the structure that prompts retrieval: semantic similarity, isomorphism, and pragmatic relevance. We describe ARCS, a program that demonstrates how these constraints can be used to select relevant analogs by forming a network of hypotheses and attempting to satisfy the constraints simultaneously. ARCS has been tested on several data bases that display both its psychological plausibility and computational power.

... paradigms of serial recall, recognition memory, free recall, and implicit memory. List memory performance in ACT-R is determined by the level of activation of declarative chunks which encode that items occur in the list. This level of activation is in turn determined by amount of rehearsal, delay, and associative fan from a list node. This theory accounts for accuracy and latency profiles in backward and forward serial recall, set size effects in the Sternberg paradigm, length–strength effects in recognition memory, the Tulving–Wiseman function, serial position, length and practice effects in free recall, and lexical priming in implicit memory paradigms. This wide variety of effects is predicted with minimal parameter variation. It is argued that the strength of the ACT-R theory is that it offers a completely specified processing architecture that serves to integrate many existing models in the literature.

This article reviews research on the use of situation models in lnguage comprehension and memory retrieval over the past 15 years. Situation models are integrated mental representations of a described state of affairs. Significant progress has been made in the scientific understanding of how situation models are involved in language comprehension and memory retrieval. Much of this research focuses on establishing the existence of situation models, often by using tasks that assess one dimension of a situation model. However, the authors argue that the time has now come for researchers to begin to take the multidimensionality of situation models seriously. The authors offer a theoretical framework and some methodological observations that may help researchers to tackle this issue.

A theory is described that provides a detailed model of how people recall serial lists of items. This theory is based on the Adaptive Character of Thought-Rational (ACT-R) production system (J. R. Anderson, 1993). It assumes that serial lists are represented as hierarchical structures consisting of Copyright 1997 by the American Psychological Association, Inc. 0033-295X/97/$3,00 groups and items within groups. Declarative knowledge units encode the position of items and of groups within larger groups. Production rules use this positional information to organize the serial recall of a list of items. In ACT-R, memory access depends on a limited-capacity activation process, and errors can occur in the contents of recall because of a partial matching process. These limitations conspire in a number of ways to produce the limitations in immediate memory span: As the span increases, activation must be divided among more elements, activation decays more with longer recall times, and there are more opportunities for positional and acoustic confusions. The theory is shown to be capable of predicting both latency and error patterns in serial recall. It addresses effects of serial position, list length, delay, word length, positional confusion, acoustic confusion, and articulatory suppression. In this article we describe our efforts to come to a detailed process understanding of the task involved in reproducing a serial list of items. This is certainly an area that has received a great deal of research, and a great many phenomena have

The fan effect (Anderson, 1974) has been attributed to interference among competing associations to a concept. Recently, it has been suggested that such effects might be due to multiple mental models (Radvansky, Spieler, & Zacks, 1993) or suppression of concepts (Anderson & Spellman, 1995; Conway & Engle, 1994). We show that the ACT-R (Adaptive Control of Thought-Rational) theory, which embodies associative interference, is consistent with the Radvansky et al results and we fail to find any evidence for concept suppression in a new fan experiment. The ACT-R model provides good quantitative fits to the results from a variety of experiments. The three key concepts in these fits are (a) the associative strength between two concepts reflect the degree to which one concept predicts the other; (b) foils are rejected by retrieving mismatching facts; and (c) subjects can adjust the relative weights they give to various cues in retrieval.

The theory outlined in the present chapter adopts a cognitive approach to motivation. In the pages that follow we describe a research program premised on the notion that the cognitive treatment affords conceptual and methodological advantages enabling new insights into problems of motivated action, self-regulation and self-control. We begin by placing our work in the broader historical context of social psychological theorizing about motivation and cognition. We then present our theoretical notions and trace their implications for a variety of psychological issues including activity-experience, goal-commitment, choice, and substitution. The gist of the chapter that follows describes our empirical research concerning a broad range of phenomena informed by the goal-systemic analysis. Motivation Versus Cognition, or Motivation as Cognition Motivation versus cognition: the “separatist program. ” Social psychological theories have often treated motivation as separate from cognition, and have often approached it in a somewhat static manner. The separatism of the “motivation versus cognition ” approach was manifest in several major formulations and debates. Thus, for example, the dissonance versus self-perception debate (Bem, 1972) pitted against each other motivational (i.e., dissonance) versus cognitive (i.e., self-perception) explanations of attitude change phenomena. A similar subsequent controversy pertained to the question of whether a motivational explanation of biased causal attributions in terms of ego-defensive tendencies (cf. Kelley, 1972) is valid, given the alternative possibility of a purely cognitive explanation (Miller & Ross, 1975). The separatism of the “motivation versus cognition ” approach assigned distinct functions to motivational and cognitive variables. This is apparent in major social psychological notions of persuasion, judgment or impression formation. For instance, in the popular dual-mode theories of

plans are probabilistic summaries of specific plans, containing pointers to their components -- abstract states, operators, and subplans -- along with associated probabilities. For example, a generic plan for picking up an object (a manipulation plan) might have three subproblems, analogous to the event described above. Icarus uses the same approach to store route knowledge (navigation plans), with places acting as states and with operators like move and turn. Components of Icarus Our designs for the Icarus architecture call for three main components: a perceptual system (Argus), a planning system (Daedalus), and an execution system (Maeander). Argus and Daedalus invoke the memory system (Labyrinth) to retrieve structured experiences from long-term memory, which include objects, states, and plans. 1 Labyrinth first sorts each component of an experience through memory, starting at the root node of the memory hierarchy. At each level, the memory system uses an evaluation function ca...

memory retrieval