Stressful life events and symptoms: A longitudinal model.

245 males (mean age 46.8 yrs) and 248 females (mean age 44 yrs) were readministered the Social Readjustment Rating Scale, measures of personal functioning, and a social background index 12–15 mo after their initial assessment. There was some evidence for temporal consistency in the number and type of events Ss experienced as well as for a relationship between initial symptoms of depression (among males) and the more frequent occurrence of later events. After controlling for Ss' initial symptom levels and propensity to experience stressful events, an increase in negative events during the follow-up period was related to an increase in symptoms. Among several gender differences, negative events were found to have more impact on females than males. The confounding of the measurement of discrete stressful events and ongoing life strain is identified as potentially underlying the consistency of "events" as well as contributing to the difficulty in interpreting the relationship between "events" and functioning. (53 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

From subjective probabilities to decision weights: The effect of asymmetric loss functions on the evaluation of uncertain outcomes and events.

Much of decision aiding uses a divide-and-conquer strategy to help people with risky decisions. Assessing the utility of outcomes and one's degree of belief in the likelihood are assumed to be separable tasks, the result of which can then be combined to determine the preferred alternative. Evidence from different areas of psychology now provides a growing consensus that this assumption is too simplistic. Observed dependencies in the evaluation of uncertain outcomes and the likelihood of the events giving rise to them are frequent and systematic. Dependencies seem to derive from general strategic processes that take into consideration asymmetric costs of over- vs underestimates of uncertain qualities. This asymmetric-loss-function interpretation provides a psychological explanation for observed judgments and decisions under uncertainty and links them to other judgment tasks. The decision weights estimated when applying dependent-utility models to choices are not simply reflections of perceived subjective probability but a response to several constraints, all of which modify the weight of risky or uncertain outcomes. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Extracting contact energies from protein structures: a study using a simplified model

Intracellular recordings were made in a pontine slice preparation of the rat brain containing the nucleus locus coeruleus (LC). In a first series of experiments, various parameters of spontaneous action potentials were evaluated. It turned out that ethanol (100 mM) does not alter the firing rate, the spike amplitude and the afterhyperpolarization following a spike. In subsequent experiments, the generation of action potentials was prevented by passing continuous hyperpolarizing current via the recording electrode. Under these conditions, ethanol (100 mM) had no effect on the membrane potential or input resistance. Pressure-applied N-methyl-D-aspartate (NMDA), (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and alpha,beta-methylene ATP (alpha,beta-meATP) reproducibly depolarized LC neurons. While ethanol (100 mM) depressed the NMDA- and AMPA-induced depolarization to a similar extent, it did not interact with alpha,beta-meATP. Lower concentrations of ethanol (10 and 30 mM) had no effect on depolarizing responses to NMDA or AMPA. Noradrenaline applied by pressure pulses reproducibly hyperpolarized LC cells. These hyperpolarizations were unchanged by ethanol (100 mM). Biphasic synaptic potentials consisting of early depolarizing (PSP) and late hyperpolarizing (IPSP) components were evoked by electrical stimulation. Ethanol (100 mM) depressed the PSP and increased the IPSP. Glutamatergic PSPs recorded in the combined presence of picrotoxin (100 microM) and suramin (100 microM) were also inhibited by ethanol (100 mM). However, IPSPs recorded under these conditions were insensitive to ethanol (100 mM). In conclusion, ethanol may interfere with the AMPA (or NMDA) receptor-mediated fraction of the PSP and slightly facilitate the alpha2 adrenoceptor-mediated fraction of the IPSP.     

Personality, life events, and subjective well-being: Toward a dynamic equilibrium model.

Using data from 4 waves of an Australian panel study, this study offers a dynamic account of relations between personality, life events, and subjective well-being (SWB). Members of the Victorian Quality of Life panel study were interviewed in 1981, 1983, 1985, and 1987. The initial sample size was 942; 649 respondents remain. The study shows that very stable personality traits (neuroticism, extraversion, and openness to experience) predispose people to experience moderately stable levels of favorable and adverse life events and moderately stable levels of SWB. However, contrary to previous research (P. T. Costa and R. R. McCrae, 1984) life events influence SWB over and above the effects of personality. A dynamic equilibrium (DE) model is outlined, in which each person is regarded as having "normal" equilibrium levels of life events and SWB, predictable on the basis of age and personality. Only when events deviate from their equilibrium levels does SWB change. The DE model is compared with 3 alternatives: personality models, adaptation level models, and models that treat life events as being wholly exogenous. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analyzing numerical responses: A model and its application to examples from personnel and organizational management.

We analyze the structure of the numerical responses of persons connected with money and present a mental model together with its connection to fuzzy theory. The numerical response is one single number containing information about the value and the exactness of a variable. We test the rules describing the process, generating these responses experimentally as well as using examples from a questionnaire, and provide further empirical evidence. The simultaneous determination of the value and exactness of a response resulting in one number causes severe problems in using these responses as input to decision models. We propose a pre-analysis of the data with the rules provided in this paper. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

More than just finding color: Strategy in global visual search is shaped by learned target probabilities.

In 2 experiments, eye movements were examined during searches in which elements were grouped into four 9-item clusters. The target (a red or blue T) was known in advance, and each cluster contained different numbers of target-color elements. Rather than color composition of a cluster invariantly guiding the order of search though clusters, the use of color was determined by the probability that the target would appear in a cluster of a certain color type: When the target was equally likely to be in any cluster containing the target color, fixations were directed to those clusters approximately equally, but when targets were more likely to appear in clusters with more target-color items, those clusters were likely to be fixated sooner. (The target probabilities guided search without explicit instruction.) Once fixated, the time spent within a cluster depended on the number of target-color elements, consistent with a search of only those elements. Thus, between-cluster search was influenced by global target probabilities signaled by amount of color or color ratios, whereas within-cluster search was directly driven by presence of the target color. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Simulation of eutectic solidification structures of binary alloys: a multiparticle diffusion limited aggregation model

The (isothermal) eutectic solidification structures of binary alloys have been simulated using a two-dimensional monte carlo model. The model takes into account simultaneous diffusion of all liquid atoms, incorporates the energy contributions of like and unlike nearest and next-nearest neighbor bonds in the solid on solidification, and allows surface rearrangement at the solid-liquid interface. It has been demonstrated that results obtained from this model exhibit phenomena observed during eutectic solidification in practice, for example, the passage of the growth rate through a maximum upon decreasing temperature. Particular attention has been devoted to the effect of growth parameters, such as the next nearest neighbor interaction in the solid and the surface relaxtion length, on the morphology of the growing solid phase.     

Hierarchical structures: Chunking by food type facilitates spatial memory.

Three experiments assessed the ability of male Sprague-Dawley rats to organize the spatial locations of different food types in a hierarchical manner to maximize the efficiency of working memory. Independent groups were exposed, on a 12-arm radial maze, to baiting arrangements varying in the stability of the pattern and type of food used as bait. Training rats with stable, differentiable baiting arrangements produced increased accuracy in choice performance, hierarchically ordered patterns of choice selection, slower growth of proactive interference when trials were massed, and the learning of the geometrical relations among food types independent of other extramaze cues. Such findings are strong evidence of the rat's ability to encode and use local cues for navigation, based on properties of the reinforcer. The applicaton of a chunking strategy may provide for more efficient use of working memory by facilitating information storage, recall, or resetting mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Personal vulnerability, life events, and depressive symptoms: A test of a specific interactional model.

We tested Beck's (1983) hypothesis that depressive symptoms occur when an individual experiences a negative life event that specifically matches the individual's personal motivational vulnerability. Ninety-eight undergraduates completed measures of depression level, recent life events, and sociotropic and autonomous achievement motivations. Consistent with the theory, sociotropy was associated with depression level and also served as a moderator of the relations between depression and frequency of recent negative social events. However, sociotropy also demonstrated nonpredicted interactive effects with negative events categorized a priori as autonomy related. Autonomy was unrelated to depression and showed no evidence of being a vulnerability to any type of life event. The findings generally support the value of examining the role in depression of interactions between personality characteristics and life events, although they do not support the specific matching predictions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Positive life events, attributional style, and hopefulness: Testing a model of recovery from depression.

A model of a recovery process from depression that is compatible with the hopelessness theory of depressive onset is proposed. This model predicts that depressives who have an enhancing attributional style for positive events (i.e., make global, stable attributions for such events) will be more likely to regain hopefulness and, thereby, recover from depression, when positive events occur. This prediction was tested by following a group of depressed college students longitudinally for 6 weeks. Although neither positive events alone nor attributional style alone predicted reduction in hopelessness, depressives who both showed the enhancing attributional style for positive events and experienced more positive events showed dramatic reductions in hopelessness which were accompanied by remission of depressive symptoms. Thus, attributional style for positive events may be a factor that enables some depressives to recover when positive events occur in their lives. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Similarities of hydrolytic antibodies revealed by their X-ray structures: a review

Numerous antibodies have been programmed to catalyse the hydrolysis of esters as well as other acyl transfer reactions. They were raised against stable analogues that model the structure of the tetrahedral transition states of these reactions. The three-dimensional structures of four hydrolytic antibodies complexed to their respective phosphonate transition state analogues (TSAs) reveal a similar orientation of hapten relative to the antibody. Analysis of the four combining sites suggests that residues binding the phosphonate TSA stabilise the oxyanion intermediate of the reaction and play a preponderant role in catalysis. Comparison of catalytic antibodies selected from the same hybridoma fusion indicates a high similarity of the motifs that catalyse the hydrolysis of a given substrate.     

Beyond belief bias: reasoning from conceptual structures by mental models manipulation

Mental models constitute an alternative to the rule-based systems in the explanation of human reasoning (Johnson-Laird, 1983). In this paper, we claim that the concept of believability generally used to categorize content and context effects is of little use within a semantic theory. Thus, we propose the use of categories that are directly extracted from subjective relations among concepts within the reasoning problem. We demonstrate that manipulations based on this kind of categorization produce predictable patterns of responses in reasoning problems. We present two experiments to test our predictions, using conditional and syllogistic reasoning problems, and in both cases, we demonstrate the influence of conceptual knowledge not only in natural contexts, but also in experimentally created artificial contexts.     

Methodological considerations in participant event monitoring of low-base-rate events in health psychology: Children's injuries as a model.

The present article outlines the advantages of the participant event monitoring methodology for the investigation of unpredictable, low-base-rate events in children. Several methods for assessing the quality of participant event monitoring data are advanced with a data set showing participant event monitoring of children's minor injuries by 61 children and their mothers. Child–mother correspondence and debriefing data suggest good accuracy for frequency estimates. Home- and laboratory-based simulations illustrate the participant event monitors' accuracy for major details. Traditional measures of data quality show good overall coder and test–retest reliability, and cross-observer reports show acceptable estimates of validity for objective aspects of the events and the expected lower estimates for the more subjective aspects. Conceptual and pragmatic difficulties of the method are considered, and suggestions for future research are advanced. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aversive schedules with independent probabilities of reinforcement for responding and not responding by rhesus monkeys: I. With signal.

Applied 2 independent probabilities of electric shock presentation to 12 naive male rhesus monkeys (Macaca mulatta) as the independent variables defining schedules of aversive control: (a) the probability that a fixed signal period would end with a shock if a specified response were made and (b) the probability that the fixed signal period would end with shock if a specified response were not made. Systematic changes in the probability values generated several familiar schedules of aversive control, as well as several intermittent procedures. Response rate tended to rise during the signal period when the probability values were set so that not responding was more likely to produce a shock than responding; response rate tended to fall during the signal period when the probabilities were set so that responding was more likely to produce shock than not responding. Response patterning in time was also evident during the interval between signals when no consequences were programmed. These characteristics of response patterning reflected the changes in the 2 independent probability variables in ways that simple measures of response rate and shock rate alone did not. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aversive schedules with independent probabilities of reinforcement for responding and not responding by rhesus monkeys: II. Without signal.

Manipulated independently the probabilities of aversive stimulus presentation given the occurrence or the nonocurrence of a leverpress response. 10 naive male rhesus monkeys (Macaca mulatta) were divided into 5 groups, each group receiving a different sequence of the 2 probabilities and thereby a different sequence of electric shock presentation schedules ranging between avoidance and punishment. The schedules provided systematic control both of the amount of response facilitation that occurred when response-produced shocks were first introduced following avoidance training and of the postfacilitation response rate decline. When the probability of shock presentation following a response was less than that for not responding, scalloped response patterns occurred; when the relative shock probabilities were reversed, bipeak response patterns were observed. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)