Overcoming contextual limitations on problem-solving transfer.

Five experiments investigated transfer from multiple analogs to a superficially dissimilar target problem. When subjects explicitly compared the analogs and then immediately attempted to solve the target problem in the context of a single experiment, transfer was obtained with significant frequency even without a hint that the analogs and target were related. Prehint transfer was sharply reduced or eliminated when the source analogs and the target were presented in different contexts, even when the transfer test was immediate. However, prehint transfer was enhanced, even after a context shift and a week-long delay between reading the source analogs and solving the problem, when the following conditions were met: The target problem was reworded slightly to emphasize a structural feature that it shared with the analogs; three rather than two source analogs were provided; and detailed, schema-oriented questions were used to help subjects focus on the problem-relevant aspects of the stories. Although spontaneous transfer between small numbers of dissimilar analogs is difficult to obtain, it can be achieved by manipulations that foster abstraction of a problem schema from the training examples. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Activity of the plasma membrane H(+)-ATPase and optimal glycolytic flux are required for rapid adaptation and growth of Saccharomyces cerevisiae in the presence of the weak-acid preservative sorbic acid

The weak acid sorbic acid transiently inhibited the growth of Saccharomyces cerevisiae in media at low pH. During a lag period, the length of which depended on the severity of this weak-acid stress, yeast cells appeared to adapt to this stress, eventually recovering and growing normally. This adaptation to weak-acid stress was not due to metabolism and removal of the sorbic acid. A pma1-205 mutant, with about half the normal membrane H+-ATPase activity, was shown to be more sensitive to sorbic acid than its parent. Sorbic acid appeared to stimulate plasma membrane H+-ATPase activity in both PMA1 and pma1-205. Consistent with this, cellular ATP levels showed drastic reductions, the extent of which depended on the severity of weak-acid stress. The weak acid did not appear to affect the synthesis of ATP because CO2 production and O2 consumption were not affected significantly in PMA1 and pma1-205 cells. However, a glycolytic mutant, with about one-third the normal pyruvate kinase and phosphofructokinase activity and hence a reduced capacity to generate ATP, was more sensitive to sorbic acid than its isogenic parent. These data are consistent with the idea that adaptation by yeast cells to sorbic acid is dependent on (i) the restoration of internal pH via the export of protons by the membrane H+-ATPase in an energy-demanding process and (ii) the generation of sufficient ATP to drive this process and still allow growth.     

The emergence of coherence over the course of decision making.

Previous research has indicated that decision making is accompanied by an increase in the coherence of assessments of the factors related to the decision alternatives. In the present study, the authors investigated whether this coherence shift is obtained before people commit to a decision, and whether it is obtained in the course of a number of other processing tasks. College students were presented with a complex legal case involving multiple conflicting arguments. Participants rated agreement with the individual arguments in isolation before seeing the case and after processing it under various initial sets, including playing the role of a judge assigned to decide the case. Coherence shifts were observed when participants were instructed to delay making the decision (Experiment 1), to memorize the case (Experiment 2), and to comprehend the case (Experiment 3). The findings support the hypothesis that a coherence-generating mechanism operates in a variety of processing tasks, including decision making. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of causal models in analogical inference.

Computational models of analogy have assumed that the strength of an inductive inference about the target is based directly on similarity of the analogs and in particular on shared higher order relations. In contrast, work in philosophy of science suggests that analogical inference is also guided by causal models of the source and target. In 3 experiments, the authors explored the possibility that people may use causal models to assess the strength of analogical inferences. Experiments 1-2 showed that reducing analogical overlap by eliminating a shared causal relation (a preventive cause present in the source) from the target increased inductive strength even though it decreased similarity of the analogs. These findings were extended in Experiment 3 to cross-domain analogical inferences based on correspondences between higher order causal relations. Analogical inference appears to be mediated by building and then running a causal model. The implications of the present findings for theories of both analogy and causal inference are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bidirectional reasoning in decision making by constraint satisfaction.

Recent constraint satisfaction models of explanation, analogy, and decision making claim that these processes are influenced by bidirectional constraints that promote coherence. College students were asked to reach a verdict in a complex legal case involving multiple conflicting arguments, including alternative analogies to the target case. Participants rated agreement with the individual arguments both in isolation before seeing the case and again after reaching a verdict. Assessments of the individual arguments shifted so as to cohere with their emerging verdict. A cascade of spreading coherence influenced decisions made about a subsequent case involving different legal issues. Participants' memory for their initial positions also shifted so as to cohere with their final positions. The results demonstrate that constraint satisfaction can transform ambiguous inputs into coherent decisions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distributed representations of structure: A theory of analogical access and mapping.

This article describes an integrated theory of analogical access and mapping, instantiated in a computational model called LISA (Learning and Inference with Schemas and Analogies). LISA represents predicates and objects as distributed patterns of activation that are dynamically bound into propositional structures, thereby achieving both the flexibility of a connectionist system and the structure sensitivity of a symbolic system. The model treats access and mapping as types of guided pattern classification, differing only in that mapping is augmented by a capacity to learn new correspondences. The resulting model simulates a wide range of empirical findings concerning human analogical access and mapping. LISA also has a number of inherent limitations, including capacity limits, that arise in human reasoning and suggests a specific computational account of these limitations. Extensions of this approach also account for analogical inference and schema induction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibitory action of a truncated derivative of the amphibian skin peptide dermaseptin s3 on Saccharomyces cerevisiae

The inhibitory activity of a truncated derivative of the natural amphibian skin peptide dermaseptin s3-(1-16)-NH2 [DS s3 (1-16)] against Saccharomyces cerevisiae was studied. Significant growth inhibition was observed after exposure to 3.45 microgram of the peptide per ml at pH 6.0 and 7.0, with complete growth inhibition occurring at 8.63 microgram of peptide per ml for all pH values tested. Using confocal scanning laser microscopy, we have shown that DS s3 (1-16) disrupted the yeast cell membrane resulting in the gross permeabilization of the cell to the nuclear stain ethidium bromide. However, the principal inhibitory action of the peptide was not due to disruption of intracellular pH homeostasis. Instead, growth inhibition by the peptide correlated with the efflux of important cellular constituents such as ADP, ATP, RNA, and DNA into the surrounding medium. The combination of DS s3 (1-16) with mild heating temperatures as low as 35 degreesC significantly enhanced the inhibitory effect of the peptide (8.63 microgram/ml), and at 45 degreesC greater than 99% of the population was killed in 10 min. In summary, a derivative of a natural antimicrobial peptide has potential, either alone or in combination with mild heating, to prevent the growth of or kill spoilage yeast.     

Analogical and category-based inference: A theoretical integration with Bayesian causal models.

A fundamental issue for theories of human induction is to specify constraints on potential inferences. For inferences based on shared category membership, an analogy, and/or a relational schema, it appears that the basic goal of induction is to make accurate and goal-relevant inferences that are sensitive to uncertainty. People can use source information at various levels of abstraction (including both specific instances and more general categories), coupled with prior causal knowledge, to build a causal model for a target situation, which in turn constrains inferences about the target. We propose a computational theory in the framework of Bayesian inference and test its predictions (parameter-free for the cases we consider) in a series of experiments in which people were asked to assess the probabilities of various causal predictions and attributions about a target on the basis of source knowledge about generative and preventive causes. The theory proved successful in accounting for systematic patterns of judgments about interrelated types of causal inferences, including evidence that analogical inferences are partially dissociable from overall mapping quality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Causal models and the acquisition of category structure.

This article proposes that learning of categories based on cause-effect relations is guided by causal models. In addition to incorporating domain-specific knowledge, causal models can be based on knowledge of such general structural properties as the direction of the causal arrow and the variability of causal variables. Five experiments tested the influence of common-cause models and common-effect models on the ease of learning linearly separable and nonlinearly separable categories. The results show that causal models guide the interpretation of otherwise identical learning inputs, and that learning difficulty is determined by the fit between the structural implications of the causal models and the structure of the learning domain. These influences of the general properties of causal models were obtained across several different content domains, including domains for which subjects lacked prior knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The analogical mind.

The use of analogy in human thinking is examined from the perspective of a multiconstraint theory, which postulates 3 basic types of constraints: similarity, structure, and purpose. The operation of these constraints is apparent in laboratory experiments on analogy and in naturalistic settings, including politics, psychotherapy, and scientific research. The multiconstraint theory has been implemented in detailed computational simulations of the analogical human mind. (PsycINFO Database Record (c) 2010 APA, all rights reserved)