Planning and acting

A new theory of problem solving is presented, which embeds problem solving in the theory of action; in this theory, a problem is just a difficult action. Making this work requires a sophisticated language for-talking about plans and their execution. This language allows a broad range of types of action, and can also be used to express rules for choosing and scheduling plans. To ensure flexibility, the problem solver consists of an interpreter driven by a theorem prover which actually manipulates formulas of the language. Many examples of the use of the system six given. including an extended treatment of the world of blocks. Limitations and extensions of the system are discussed at length. It is concluded that a rule-based problem solver is necessary and feasible, but that much more work remains to be done on the underlying theory of planning and acting.     

Physical child abuse: A dual-component analysis

Previous etiological models of child abuse are reviewed, with particular emphasis on the current social interactional analysis. It is argued that while this model accounts for the documented correlates of abuse, it fails to provide a plausible mechanism for explaining the rapid acceleration from low- to high-intensity punitive behavior characteristic of abusive episodes. Drawing from research on interpersonal aggression by Berkowitz, Zillmann, and other social psychologists, a model is developed in which an arousal-mediated respondent component is added to the current instrumentally based punitive processes. Implications of this improved analysis for treatment and prevention are considered.     

Methodological issues in language acquisition research with very young children

It is suggested that the dominance of observational methods in child language research with very young children has limited progress in understanding the language acquisition process. Evidence is presented that, contrary to popular belief, naturalistic methods do not guarantee ecological validity, nor are they free of task biases. Furthermore, observational studies do not necessarily provide better measures of linguistic competence than do more structured methods. Instead, it is argued that new insights from cognitive developmental research are applicable in studying language production in children younger than 3 years. A number of structured techniques are reviewed that have been used or could be used to study language production. It is concluded that a combination of methods is necessary in order to disentangle and control the many variables that enter into the language acquisition process.     

Remembering,understanding, and representation

Starting with the facts that not everything that is understood is remembered, and that not everything that is remembered is understood. this paper urges that models of language processing should be able to make a distinction between comprehension and memory. To this end. a case is made for a spreading activation process as being the essential ingredient of the comprehension process. It is argued that concepts activated during comprehension not only restrict the search set for candidate concepts to be used in a top-down fashion, they also constitute part of an episodic representation that can come to be p e of long-term memory. The way in which these representations atrophy is discussed, as is the way in which their idiosyncratic components are eliminated in producing representations in semantic memory. Some observations on the comprehension and memory of text are made and arguments are presented to show how intrusions and omissions in recall can be handled. Some existing experimental data is reanalyzed in terms of the proposed model and alternative interpretations consistent with the model are shown to be possible.     

An attempt to understand students' understanding of basic algebra

This paper reports the results obtained with a group of 24 14-year-old students when presented with a set of algebra tasks by the Leeds Modelling System, LMS. These same students were given a comparable paper-and-pencil test and detailed interviews some four months later. The latter studies uncovered several kinds of student misunderstandings that LMS had not detected. Some students had profound misunderstandings of algebraic notation: Others used strategies such as substituting numbers for variables until the equation balanced. Additionally, it appears that the student errors fall into several distinct classes: namely, manipulative, parsing, clerical, and “random.” LMS and its rule database have been enhanced as the result of this experiment, and LMS is now able to diagnose the majority of the errors encountered in this experiment. Finally, the paper gives a process-oriented explanation for student errors, and re-examines related work in cognitive modelling in the light of the types of student errors reported in this experiment. Misgeneralization is a mechanism suggested to explain some of the mal-rules noted in this study.     

The cognitive structure of social categories

Support for the prototype theory of categorization was found in a study of the structure of social categories. Though occupational terms such as DOCTOR are socially defined, they do not have the classical structure their clear definitional origins would predict. Conceptions of social categories are richer and more complex than those of physical object categories and subjects agree upon them. Comparison of various instructions for eliciting attributes of categories showed that whether subjects are asked to define a term, give characteristics, or describe ways they recognize members of categories, the attributes they list contribute to a prototype structure. These data provide evidence against the view that prototype structure is relevant only to an identification procedure and not to the core of concepts, as has been suggested.     

Languages and designs for probability judgment

Theories of subjective probability are viewed as formal languages for analyzing evidence and expressing degrees of belief. This article focuses on two probability langauges, the Bayesian language and the language of belief functions (Shafer, 1976). We describe and compare the semantics (i.e., the meaning of the scale) and the syntax (i.e., the formal calculus) of these languages. We also investigate some of the designs for probability judgment afforded by the two languages.     

Rules and topics in conversation

Rules of conversation are given that specify what can follow what. A system for deciding what makes a reasonable subject for a conversation is shown. Topics are discussed and rules for topic shift are presented.