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D Klahr

Publications and source records attributed to D Klahr.

8 recordsLinked to original sources
PubMed1996

When to trust the data: further investigations of system error in a scientific reasoning task.

When evaluating experimental evidence, how do people deal with the possibility that some of the feedback is erroneous? The potential for error means that evidence evaluation must include decisions about when to "trust the data." In this paper we present two studies that focus on subjects' responses to erroneous feedback in a hypothesis testing situation-a variant of Wason's (1960) 2-4-6 rule discovery task in which some feedback was subject to system error: "hits" were reported as "misses" and vice versa. Our results show that, in contrast to previous research, people are equally adept at identifying false negatives and false positives; further, successful subjects were less likely to use a positive test strategy (Klayman & Ha, 1987) than were unsuccessful subjects. Finally, although others have found that generating possible hypotheses prior to experimentation increases success and task efficiency, such a manipulation did little to mitigate the effects of system error.

Adult↗
PubMed1996

Knowing about guessing and guessing about knowing: preschoolers' understanding of indeterminacy.

In this article we investigate preschool children's understanding of indeterminacy by examining their ability to distinguish between determinate situations--in which the available evidence eliminates all uncertainty about an outcome--and indeterminate situations--in which it does not. We argue that a full understanding of indeterminacy requires the coordination of 3 processes: search, evaluation, and mapping. We describe 3 experiments aimed at discovering the extent to which these processes, each of which has been implicated in previous accounts of indeterminate reasoning, are developed in preschoolers and the extent to which different children organize the processes into different strategies. Experiment 1 examines 5-year-olds' performance on 1- versus 2-solution problems having different configurations of irrelevant information. Experiments 2 and 3 extend the possible sources of indeterminacy from 2 to 4 and vary the amount of consistent, inconsistent, and to-be-discovered evidence. Our results show that 4- and 5-year-old children readily give "Can tell" responses to determinate problems, as well as "Can't tell" responses when they think that the evidence warrants such a response. In addition, we report 2 new findings: (a) different children use different strategies to process determinate evidence, and these strategies, in turn, predict their performance on indeterminate problems; (b) evidence patterns in which a single positive instance is contrasted with 1 or more negative or unknown instances are particularly difficult to resolve. Many children use a decision rule--the Positive Capture rule--that produces consistent errors on this type of problem.

Age Factors↗
PubMed1996

The interaction of domain-specific knowledge and domain-general discovery strategies: a study with sinking objects.

Recent work on scientific reasoning has largely focused on either domain-specific content knowledge or domain-general reasoning knowledge. This study investigated the interaction between the 2 types of knowledge in a real-world domain in which strict control of variables was not possible. We used a context, sinking objects, in which 10-, 12-, and, 14-year-old children's strong a priori beliefs could be revealed by participant-designed experiments. The results showed that most children initially believed weight alone determined an object's sinking rate. Older, but not younger, participants typically viewed experimentation as a means of exploring the effects of attributes other than weight. However, experimentation did help all children to understand the effects of object shape and material on sinking rates. The results suggests a number of questions for further research, including how children come to understand experimentation as a matter of evaluation rather than demonstration, and the role of unexpected experimental results in driving conceptual understanding.

Adolescent↗
PubMed1993

Heuristics for scientific experimentation: a developmental study.

Scientific discovery involves search in a space of hypotheses and a space of experiments. We describe an investigation of developmental differences in the search constraint heuristics used in scientific reasoning. Sixty-four subjects (technically trained college students, community college students with little technical training, 6th graders, and 3rd graders) were taught how to use a programmable robot. Then they were presented with a new operation, provided with a hypothesis about how it might work, and asked to conduct experiments to discover how the new operation really did work. The suggested hypothesis was always incorrect, as subjects could discover if they wrote informative experiments, and it was either plausible or implausible. The rule for how the unknown operation actually worked was either very similar or very dissimilar to the given hypothesis. Children focused primarily on plausible hypotheses, conducted a limited set of experiments, designed experiments that were difficult to interpret, and were unable to induce implausible (but correct) hypotheses from data. Adults were much better than children in discovering implausible rules. The performance deficits we found were not simply the result of children's inadequate encoding or mnemonic skills. Instead, the adults appear to use domain-general skills that go beyond the logic of confirmation and disconfirmation and deal with the coordination of search in two spaces: a space of hypotheses and a space of experiments.

Adolescent↗