This study examines four months of online discourse of 22 Grade 4 students engaged in efforts to advance their understanding of optics. Their work is part of a school-wide knowledge building initiative, the essence of which is giving students collective responsibility for idea improvement. This goal is supported by software-Knowledge Forum-designed to provide a public and collaborative space for continual improvement of ideas. A new analytic tool-inquiry threads-was developed to analyze the discourse used by these students as they worked in this environment. Data analyses focus on four knowledge building principles: idea improvement; real ideas, authentic problems (involving concrete/empirical and abstract/conceptual artifacts); community knowledge (knowledge constructed for the benefit of the community as a whole); and constructive use of authoritative sources. Results indicate that these young students generated theories and explanation-seeking questions, designed experiments to produce real-world empirical data to support their theories, located and introduced expert resources, revised ideas, and responded to problems and ideas that emerged as community knowledge

Three experiments explored the conditions under which information presented in the first part of an experiment facilitates the subsequent solving of simple insight problems. We argue that previous unsuccessful attempts to obtain such facilitation are attributable to the experimenters' failure to present this information in a form that induces the conceptual operations needed to solve the problem. Substantial facilitation is obtained if the information is presented in a form that induces a few seconds of puzzlement and then a clue is presented that leads to an appropriate reconception; if identical information is presented without such a period of puzzlement and reconception, no facilitation is observed. The results demonstrate that conceptual processing operations, not merely informational content, must be relevant if conceptual transfer is to occur. One possible mechanism involved in such transfer is the indexing of concepts such that they contain pointers to conceptually anomalous episodes.

We performed three experiments on recognition learning that tested for the existence of a replacement effect (i.e., the benefit accruing to nonrecognized items, or targets, when recognized items are replaced in the next study trial). A reverse Rock substitution procedure was used, and the replacement effect occurred in all three experiments. The results were interpreted in terms of a distributed memory model, the matched-filter model of Anderson (1973), but several modifications were necessary. The original version cannot learn, and a closed-loop modification did not show the repetition effect that was clearly evident in the data. The most satisfactory version was one based on probabilistic encoding of features in the item vectors, and it seemed capable of explaining most aspects of the data.Recent developments in distributed memory models provide a new way of looking at human memory. They specify how information can be stored and retrieved, they explain how recognition and recall can occur, and, coupled with a decision system, they can account for both accuracy and latency data. They are content addressable, and retrieval occurs by direct access rather than by search. They are consistent with known physiological mechanisms; in fact, many distributed memory models (see Hinton & Anderson, 1981) are based on or are outgrowths from neural models.Originally, it was not clear how to test distribut¢ memory models, so their usefulness to experimental psychologists was limited. However, a number of applications to experimental data have appeared more recently (e.g., Anderson, 1973;Anderson, Silverstein, Ritz, & Jones, 1977;Eich, 1982Eich, , 1985Heath, 1983; Humphreys, Pike, Bain, & Tehan, in press;Kawamoto & Anderson, 1985;Knapp & Anderson, 1984;Lewandowsky & Hockley, 1987; McDowd & Murdock, 1986;Murdock, 1982Murdock, , 1983 Nilsson, 1986), so the models can clearly make contact with experimental data.A further test is whether distributed memory models predict any novel or unexpected empirical phenomena. We argue that they do, and illustrate with a particular example. The prediction to be tested is that in a recognition learning situation, replacing items recognized on one trial should facilitate recognition of the repeated items (' 'targets") on the next trial. This facilitation is relative to a control condition in which there is no replacement.More specifically, in the experimental or replacement condition, one replaces all items recognized on the test phase of Trial n -1 with a new sample of items for the This work was supported by Natural Sciences and Engineering Research Council of Canada Grant APA 146 to Bennet B. Murdock, lr. We would like to thank our colleagues for many helpful comments on this research. Requests for reprints should be sent to Bennet Murdock. Department of Psychology, University of Toronto, Toronto, ON M5S IAI, Canada. 91 study phase of Trial n. In the control or nonreplacement condition, all old items from Trial n -1 are repeated in the study phase of Trial n. The prediction is that performa...

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Following 4 unilateral contractions of hand muscles, subjects told stories about pictures from the T.A.T. A propositional analysis of the stories showed that the emotional tone of stories told following left hand contractions were more negative than those told after right hand contractions. These results are comparable to those reported following unilateral facial contractions and are consistent with the arousal of the emotional properties of the hemisphere contralateral to the contractions. When the stories were compared to ones told in a control, no contraction condition, it was found that the differences between the left and right contractions were attributable to the effects of either one or the other depending on the control condition responses to the pictures. The results therefore provide evidence for both left and right hemisphere involvement in emotion.