No abstract

The fast-and-frugal heuristics approach to decision making under uncertainty advocated by Gigerenzer and colleagues (e.g., Gigerenzer & Goldstein, 1996) has achieved great popularity despite a relative lack of empirical validation. We report two experiments that examine the use of one particular heuristic-''take-the-best'' (TTB). In both experiments the majority of participants adopted frugal strategies, but only one-third (33%) behaved in a manner completely consistent with TTBÕs search, stopping and decision rules. Furthermore, a significant proportion of participants in both experiments adopted a non-frugal strategy in which they accumulated more information than was predicted by TTBÕs stopping rule. The results provide an insight into the conditions under which different heuristics are used, and question the predictive power of the fast-and-frugal approach.

Examination of search strategies has tended to focus on choices determined by decision makers' personal preferences among relevant cues, and not on learning cue-criterion relationships. We present an empirical and rational analysis of cue search for environments with objective criteria. In such environments, cues can be evaluated on the basis of three properties: validity (the probability that a cue identifies the correct choice if cue values differ between alternatives); discrimination rate (the proportion of occasions on which a cue has differing values); and success (the expected proportion of correct choices when only that cue can be used). Our experiments show that though there is a high degree of individual variability, success is a key determinant of search. Furthermore, a rational analysis demonstrates why success-directed search is the most adaptive strategy in many circumstances. Copyright # 2004 John Wiley & Sons, Ltd. key words search strategies; heuristics; cue hierarchies, adaptive behaviors When faced with a decision it is often impossible to consider all of the options, their attributes and their potential consequences simultaneously, so we must do so sequentially. The order that we adopt to dictate this sequential search may have profound effects on our decisions and the consequences of those decisions (Hastie & Dawes, 2001). In this paper we present a new conceptualization of search in decision making in which search is dictated by the ''success'' of information in predicting the correct outcomes of decisions. Success is a function of the likelihood that a piece of information is usable and its accuracy in leading to a correct inference. We report empirical evidence showing that people's search patterns are allied to those determined by success, and a rational analysis that demonstrates the variety of circumstances in which success-directed search achieves the best outcomes.Decision making can be considered to have three component processes: information acquisition; evaluation/action; and feedback/learning (Einhorn & Hogarth, 1981;Payne, 1982). Arguably, information acquisition has received the least attention of these three aspects. Indeed, Anderson (1990) notes that the literature

No abstract

Significance Stem-cell microenvironment has been identified as an important modulator of plasticity, self-renewal, and differentiation. This work details the development of a hydrogel system tailored to promote human pluripotent stem cell (HPSC) self-renewal with a simple chemical microenvironmental switch to direct differentiation. Furthermore, the timing of switching post hydrogel fabrication can promote specific lineage differentiation as in vivo. This system highlights the role of microenvironment on fate choices of pluripotent cells and demonstrates that it may be tailored to control differentiation in vitro. Importantly, this approach may improve the generation of fully differentiated tissues, as demonstrated for cardiogenic differentiation. Our combination of hydrogels allows dense tissue structures to be produced from HPSCs by using a single-step process inaccessible to any current methodology.

No abstract

Macrae and Lewis (2002) showed that repeated reporting of the global dimension of Navon stimuli improved performance in a subsequent face identification task, whilst reporting the features of the Navon stimuli impaired performance. Using a face composite task, which is assumed to require featural processing, Weston and Perfect (2005) showed the complementary pattern: Featural responding to Navon letters speeded performance. However, both studies used Navon stimuli with global precedence, in which the overall configuration is easier to report than the features. Here we replicate the two studies above, whilst manipulating the precedence (global or featural) of the letter stimuli in the orientation task. Both studies replicated the previously reported findings with global precedence stimuli, but showed the reverse pattern with local precedence stimuli. These data raise important questions as to what is transferred between the Navon orientation task and the face-processing tasks that follow.

This study aimed to assess the ecotoxicological effects of the interaction of fullerene (C60) and benzo[a]pyrene (B[a]P) on the marine mussel, Mytilus galloprovincialis. The uptake of nC60, B[a]P and mixtures of nC60 and B[a]P into tissues was confirmed by Gas Chromatography–Mass Spectrometry (GC–MS), Liquid Chromatography–High Resolution Mass Spectrometry (LC–HRMS) and Inductively Coupled Plasma Mass Spectrometer (ICP–MS). Biomarkers of DNA damage as well as proteomics analysis were applied to unravel the interactive effect of B[a]P and C60. Antagonistic responses were observed at the genotoxic and proteomic level. Differentially expressed proteins (DEPs) were only identified in the B[a]P single exposure and the B[a]P mixture exposure groups containing 1 mg/L of C60, the majority of which were downregulated (~52%). No DEPs were identified at any of the concentrations of nC60 (p < 0.05, 1% FDR). Using DEPs identified at a threshold of (p < 0.05; B[a]P and B[a]P mixture with nC60), gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis indicated that these proteins were enriched with a broad spectrum of biological processes and pathways, including those broadly associated with protein processing, cellular processes and environmental information processing. Among those significantly enriched pathways, the ribosome was consistently the top enriched term irrespective of treatment or concentration and plays an important role as the site of biological protein synthesis and translation. Our results demonstrate the complex multi-modal response to environmental stressors in M. galloprovincialis.