Similarity-Based and Explanation-Based Learning of Explanatory and Nonexplanatory Information

We suggest that human learners employ both similarity-based learning (SBL) and explanation-based learning (EBL) procedures and that the successful use of these procedures is determined by the characteristics of the information to be learned. In a domain without underlying causal structure, multiple examples can lead to successful SBL, but not to successful EBL. In a domain with underlying causal structure, the use of appropriate background knowledge can lead to successful EBL, but not to SBL. A series of experiments was carried out in which a common initial passage was followed with a variety of different types of information (a second similar instance, a second contrasting instance, frequency data, or explanations). EBL occurred only when subjects had sufficient background knowledge and when the information to be learned could be causally structured. SBL occurred when there were multiple examples, even in domains without causal structure

Causal Structure in Categorization

What role does causal knowledge play in categorization? The current study tested the hypothesis that weight given to features is determined by the specific role they play within a causal structure. After learning typical symptoms of a disease, participants were asked to judge the likelihood that new patients had that disease. Half of the patients were missing one of the typical symptoms, and the other half had an extra symptom (a symptom typical of an alternative disease). For patients with a missing symptom, likelihood ratings were lower if the missing symptom was a cause of other symptoms than if it was an effect. However, for patients with an extra symptom, there was no difference between likelihood ratings when the extra symptom was a cause or an effect. These results suggest one mechanism underlying differences between experts and novices in categorization, and suggest an explanation for why different kinds of features (e. g., molecular or functional) are important for different kinds of categories (e.g., natural kinds or artifacts)

The effect of abstract versus concrete framing on judgments of biological and psychological bases of behavior

Human behavior is frequently described both in abstract, general terms and in concrete, specific terms. We asked whether these two ways of framing equivalent behaviors shift the inferences people make about the biological and psychological bases of those behaviors. In five experiments, we manipulated whether behaviors are presented concretely (i.e. with reference to a specific person, instantiated in the particular context of that person’s life) or abstractly (i.e. with reference to a category of people or behaviors across generalized contexts). People judged concretely framed behaviors to be less biologically based and, on some dimensions, more psychologically based than the same behaviors framed in the abstract. These findings held true for both mental disorders (Experiments 1 and 2) and everyday behaviors (Experiments 4 and 5) and yielded downstream consequences for the perceived efficacy of disorder treatments (Experiment 3). Implications for science educators, students of science, and members of the lay public are discussed

A Two-stage Categorization Model of Family Resemblance Sorting

A two-stage model is applied to category construction. The first stage of the model involves looking for a defining feature among exemplars and creating initial categories based on the defining features. In the second stage, overall similarity is calculated to categorize the remaining exemplars that were not classified by the defining feature. For some types of exemplar structures, family resemblance sorting emerges as a product of the two-stage model. A series of experiments was carried out to contrast the two-stage model with Anderson's induction model (Anderson, 1988)and CLUSTER/2 (Michalski & Stepp, 1983). The results showed that the two-stage model is abetter predictor of when family resemblance sorting will or will not occur

Biases in Refinement of Existing Causal Knowledge

This study describes a psychological experiment on biases that people exhibit in refining probabilistic causal knowledge. In the experiment, the effect of background knowledge was shown by manipulating the causal structure of prior knowledge provided to the subjects. It was found that later training instances affected the refinement of the background knowledge in different ways depending on the causal model initially given to the subjects. The two biases found in the current experiment are (1) knowledge refinement was conservative in the sense that background knowledge was modified as little as possible to account for the observed data and (2) weakening of an existing causal relationship resulted in automatic strengthening of a related causal relationship

The Effect of Selection Instructions on Reasoning about Thematic Content Rules in Wason's Card Selection Task

This study examined the effects of selection instruction and thematic content on subjects' reasoning performance on the Wason card selection task. Facilitation has frequently been demonstrated when subjects arc instructed to check for violations of a conditional rule that involves thematic content. We noted that the thematic rules previously used are also pragmatic rules that express regulations. We compared reasoning about two kinds of thematic rules: pragmatic and nonpragmatic. Subjects were instructed either to determine if the rule has been violated or to determine if the rule is true or false. The results indicate an interaction between instruction type and thematic rule type. Contrary to previous findings of facilitation on thematic materials with violation instructions, we found facilitation for true/false instructions relative to violation instructions on non-pragmatic content rules. These results stand in contrast to previous descriptions of true/false instructions as more difficult and cognitively demanding than violation instructions. We explain our findings in terms of differences in the inherent status of the two types of thematic rules

Causal Attribution A s Mechanism-Base d Story Construction: A n Explanation O f Th e Conjunction Fallacy A n d Th e Discounting Principle

We propose that causal attribution involves constructing a coherent story using mechanism information (i.e., the processes underlying the relationship between the cause and the effect). This processing account can explain both the conjunction effect (i.e., conjunctive explanations being rated more probable than their components) and the discounting effect (i.e., the effect of one cause being discounted when another cause is already known to be true). In the current experiment, both effects occurred with mechanism-based explanations but not with covariationbased explanations in which the cause-effect relationship was phrased in terms of covariations without referring to mechanisms. We discuss why the current results pose difficulties for previous attribution models in Psychology and Artificial Intelligence

Causal mechanisms

This chapter reviews empirical and theoretical results concerning knowledge of causal mechanisms— beliefs about how and why events are causally linked. First, it reviews the effects of mechanism knowledge, showing that mechanism knowledge can trump other cues to causality (including covariation evidence and temporal cues) and structural constraints (the Markov condition), and that mechanisms play a key role in various forms of inductive inference. Second, it examines several theories of how mechanisms are mentally represented— as associations, forces or powers, icons, abstract placeholders, networks, or schemas— and the empirical evidence bearing on each theory. Finally, it describes ways that people acquire mechanism knowledge, discussing the contributions from statistical induction, testimony, reasoning, and perception. For each of these topics, it highlights key open questions for future research

Causal mechanisms

This chapter reviews empirical and theoretical results concerning knowledge of causal mechanisms—beliefs about how and why events are causally linked. First, it reviews the effects of mechanism knowledge, showing that mechanism knowledge can override other cues to causality (including covariation evidence and temporal cues) and structural constraints (the Markov condition), and that mechanisms play a key role in various forms of inductive inference. Second, it examines several theories of how mechanisms are mentally represented—as associations, forces or powers, icons, abstract placeholders, networks, or schemas—and the empirical evidence bearing on each theory. Finally, it describes ways that people acquire mechanism knowledge, discussing the contributions from statistical induction, testimony, reasoning, and perception. For each of these topics, it highlights key open questions for future research.</p

Anti-Apoptotic Effects of SERPIN B3 and B4 via STAT6 Activation in Macrophages after Infection with Toxoplasma gondii

Toxoplasma gondii penetrates all kinds of nucleated eukaryotic cells but modulates host cells differently for its intracellular survival. In a previous study, we found out that serine protease inhibitors B3 and B4 (SERPIN B3/B4 because of their very high homology) were significantly induced in THP-1-derived macrophages infected with T. gondii through activation of STAT6. In this study, to evaluate the effects of the induced SERPIN B3/B4 on the apoptosis of T. gondii-infected THP-1 cells, we designed and tested various small interfering (si-) RNAs of SERPIN B3 or B4 in staurosporine-induced apoptosis of THP-1 cells. Anti-apoptotic characteristics of THP-1 cells after infection with T. gondii disappeared when SERPIN B3/B4 were knock-downed with gene specific si-RNAs transfected into THP-1 cells as detected by the cleaved caspase 3, poly-ADP ribose polymerase and DNA fragmentation. This anti-apoptotic effect was confirmed in SERPIN B3/B4 overexpressed HeLa cells. We also investigated whether inhibition of STAT6 affects the function of SERPIN B3/B4, and vice versa. Inhibition of SERPIN B3/B4 did not influence STAT6 expression but SERPIN B3/B4 expression was inhibited by STAT6 si-RNA transfection, which confirmed that SERPIN B3/B4 was induced under the control of STAT6 activation. These results suggest that T. gondii induces SERPIN B3/B4 expression via STAT6 activation to inhibit the apoptosis of infected THP-1 cells for longer survival of the intracellular parasites themselves