Showing papers by "Klaus Fiedler published in 2000"

A sampling approach to biases in conditional probability judgments: beyond base rate neglect and statistical format.

Abstract: Conditional probability judgments of rare events are often inflated. Early accounts assumed a general deficit in using statistical base rates. More recent approaches predict improvement when problems are presented in frequency format or refer to natural categories. The present theory focuses on sampling processes. Experiment 1 showed that a seeming advantage of frequency over probability formats is due to a confounded factor, the need to mentally transform stimulus samples. An information search paradigm was used in Experiment 2. When sampling by the predictor, the probability to be estimated, p(criterion/predictor), was conserved in the samples and judgments were quite accurate. However, when sampling by the criterion, the low base-rate event was strongly overrepresented, accounting for the entire bias. Judgments were quite sensitive to the sampled data, but failed to take sampling constraints into account, as shown in Experiments 3 and 4.

Different properties of two isoforms of annexin XIII in MDCK cells

Abstract: Annexins form a family of proteins that are widely expressed and known to bind membranes in the presence of calcium. Two isoforms of the annexin XIII subfamily are expressed in epithelia. We previously reported that annexin XIIIb is apically localized in MDCK cells and that it is involved in raft-mediated delivery of apical proteins. We have now analyzed the properties of annexin XIIIa, which differs from annexin XIIIb by a deletion of 41 amino acids in the amino-terminal domain, and is distributed both apically and basolaterally. Annexin XIIIa binding to membranes is independent of calcium but requires its myristoyl amino-terminal modification, as observed with annexin XIIIb. Our biochemical and functional data show that annexin XIIIa behaves differently in the apical and in the basolateral compartments. Whereas annexin XIIIa apically can associate with rafts independently of calcium, the basolateral pool requires calcium for this. Annexin XIIIa, like annexin XIIIb, stimulates apical transport of influenza virus hemagglutinin but, in contrast, only annexin XIIIa inhibits basolateral transport of vesicular stomatitis virus G protein. Our results suggest that annexin XIIIa and XIIIb have specific roles in epithelial cells, and because of their structural similarities, these isoforms offer interesting tools for unravelling the functions of annexins.

Expectancy‐effects without expectancies: Illusory correlations based on cue‐overlap

Abstract: Expectancy-based illusory correlations have been observed in numerous experiments. Simulations using the connectionist computer model BIAS (Fiedler, 1996) show that such illusory correlations may not always reflect expectancy biases but influences of similarity via cue-overlap. Cue-overlap means that some of the probabilistic cues that indicate the presence of one variable are also indicative of another variable. In an experiment, participants learned two novel concepts pertaining to a fictitious painter and a fictitious artistic style in separate runs. Both concepts were defined by multiple probabilistic cues observable in paintings. For half the participants, the cue systems underlying the perception of the two concepts overlapped, whereas for the other half they did not. In addition, we manipulated whether or not participants expected a positive contingency between artist and artistic style. In the second part of the experiment, a series of paintings was presented that constituted an objective zero correlation between artist and artistic style. Participants subsequent contingency judgments were assessed by direct and indirect measures. Data analyses revealed main effects for expectancy induction and cue-overlap but no interaction on the direct measure and nearly identical results on the indirect measure. Thus, cue-overlap and expectancy induction independently triggered the development of illusory correlations.