Likelihood-Based Clustering of Meta-Analytic SROC Curves

Meta-analysis of diagnostic studies experience the common problem that different studies might not be comparable since they have been using a different cut-off value for the continuous or ordered categorical diagnostic test value defining different regions for which the diagnostic test is defined to be positive. Hence specificities and sensitivities arising from different studies might vary just because the underlying cut-off value had been different. To cope with the cut-off value problem interest is usually directed towards the receiver operating characteristic (ROC) curve which consists of pairs of sensitivities and false-positive rates (1-specificity). In the context of meta-analysis one pair represents one study and the associated diagram is called an SROC curve where the S stands for “summary”. In meta-analysis of diagnostic studies emphasis has traditionally been placed on modelling this SROC curve with the intention of providing a summary measure of the diagnostic accuracy by means of an estimate of the summary ROC curve. Here, we focus instead on finding sub-groups or components in the data representing different diagnostic accuracies. The paper will consider modelling SROC curves with the Lehmann family which is characterised by one parameter only. Each single study can be represented by a specific value of that parameter. Hence we focus on the distribution of these parameter estimates and suggest modelling a potential heterogeneous or cluster structure by a mixture of specifically parameterised normal densities. We point out that this mixture is completely nonparametric and the associated mixture likelihood is well-defined and globally bounded. We use the theory and algorithms of nonparametric mixture likelihood estimation to identify a potential cluster structure in the diagnostic accuracies of the collection of studies to be analysed. Several meta-analytic applications on diagnostic studies, including AUDIT and AUDIT-C for detection of unhealthy alcohol use, the mini-mental state examination for cognitive disorders, as well as diagnostic accuracy inspection data on metal fatigue of aircraft spare parts, are discussed to illustrate the methodology.     

Relationships between restrictive mother-child interactions and anxiety of the child

Abstract

The “two-process model” postulates that there are specific associations between patterns of parental child-rearing styles and the development of the child's anxiety and coping dispositions. Besides parameters of parental feedback to the child, this model considers support and restriction to be the central dimensions of child-rearing behavior. The present study aims at assessing behavioral indicators for restriction. For this purpose, the working and intervention behavior of 47 mothers and their ten- to 13-year-old children was observed and registered during a 15-minute period of common problem-solving (putting together a difficult puzzle-like cube). In order to register processes of problem-oriented cooperation between mother and child, transitional probabilities between defined state and event classes were analyzed. Based on the theoretical definition of the child-rearing style “restrictio”, hypotheses concerning the significance of variable transitional probabilities are formulated and tested regarding their correspondence with anxiety-related characteristics of the child.     

Negative perfectionism increases the risk of fatigue following a period of stress

Abstract

There is a considerable amount of research concerning (he relationship between psychological variables and the postoperative outcome of surgery. However, little attention has been paid to the potential influence of psychological factors on infra-operative variables, most notably on anaesthetic requirement. The present study investigates the influence of surgery-related trail and slate anxiety as well as of dispositional and surgery-related actual coping on several indicators of intra- and postoperative adjustment. In addition, a possible mediating effect of stress-induced analgesia on the relationships between anxiety, coping, and intraoperative anaesthetic requirements was evaluated. Sixty-one patients undergoing elective lumbar iniclcotomy completed questionnaires regarding anxiety and coping variables one day before surgery. Intraoperative adjustment was assessed by measuring EEG-controlled anaesthetic requirements for induction and maintenance of anaesthesia, β-endorphin plasma concentration was collected preoperatively in the induction room. Postoperative outcome was assessed on the third day after surgery by questionnaires regarding pain experience, physical condition and emotional state. For preoperative anxiety as well as vigilant coping behaviour, there were opposite relationships with subjective measures of adjustment (e.g. self-reported postoperative pain experience), on the one side, and objective measures on the other (e.g., intraoperative anaesthetic requirement). Stress-induced analgesia was found for the subgroup of high-anxious patients. The results indicate that psychological programmes aimed at facilitating patients' perioperative adjustment should consider the different effects of anxiety and coping on subjective and objective measures.     

Number Judgment of Postage Stamps: A Contribution to the Psychology of Social Norms

PBI teems with unanswered questions regarding location, relative position, size, color, shape, movement, magnification, and what, precisely, is being observed. A novel experimental design is suggested which might permit sustained observation of PBI with use of facilitating flicker with a quasi-moving but motionless stimulus and a stationary eye.     

Alcohol and aggression without consumption. Alcohol cues, aggressive thoughts, and hostile perception bias

Researchers and the lay public have long known of a link between alcohol and aggression. However, whether this link results from alcohol's pharmacological effects or is merely an artifact of the belief that alcohol has been consumed (i.e., placebo effect) has been debated. The current experiments examined the propensity for alcohol-related cues to elicit aggressive thoughts and hostile perceptions in the absence of alcohol or placebo consumption. In Experiment 1, participants made faster lexical decisions concerning aggression-related words following alcohol-related primes compared with neutral primes. In Experiment 2, participants who first were exposed to alcohol advertisements subsequently rated the behavior of a target person as more hostile than participants who initially viewed control advertisements. Furthermore, this effect was largest among participants who most strongly associated alcohol and aggression. Findings are discussed in terms of semantic network theory and links in memory between alcohol and its anticipated effects.     

Serotonergic dysfunction: Brain imaging and behavioral correlates

Identification of gene-environment and gene-gene interactions has become increasingly important in understanding psychiatric disorders. Dysfunction of central serotonergic neurotransmission has been implicated in alcoholism, depression, and anxiety. We review the literature on nonhuman primates that assesses the interaction between the genetic constitution of the regulatory region of the serotonin transporter (5-HTT) and environmental factors. Prospective studies in nonhuman primates that underwent social stress found a reduction of the serotonin turnover rate among carriers of one or two short alleles in a functional polymorphism of the 5-HTT promoter. In these primates, brain imaging studies showed a relative increase in the availability of raphe serotonin transporters. A low serotonin turnover rate and a high availability of serotonin transporters were associated with reduced response to excessive alcohol intake, anxiety, and impulsive aggression. Animal experiments point to a relationship between serotonergic dysfunction, negative mood states, and excessive alcohol intake, which may in part be mediated by reduced alcohol-induced sedation.     

Prechtl's assessment of general movements: a diagnostic tool for the functional assessment of the young nervous system

General movements (GMs) are part of the spontaneous movement repertoire and are present from early fetal life onwards until the end of the first half a year of life. GMs are complex, occur frequently, and last long enough to be observed properly. They involve the whole body in a variable sequence of arm, leg, neck, and trunk movements. They wax and wane in intensity, force and speed, and they have a gradual beginning and end. Rotations along the axis of the limbs and slight changes in the direction of movements make them fluent and elegant and create the impression of complexity and variability. If the nervous system is impaired, GMs loose their complex and variable character and become monotonous and poor. Two specific abnormal GM patterns reliably predict later cerebral palsy: 1) a persistent pattern of cramped-synchronized GMs. The movements appear rigid and lack the normal smooth and fluent character. Limb and trunk muscles contract and relax almost simultaneously. 2) The absence of GMs of fidgety character. So-called fidgety movements are small movements of moderate speed with variable acceleration of neck, trunk, and limbs in all directions. Normally, they are the predominant movement pattern in an awake infant at 3 to 5 months. Beside a sensitivity and specificity of 95% each, the assessment of GMs is quick, noninvasive, even nonintrusive, and cost-effective compared with other techniques, e.g., magnetic resonance imaging, brain ultrasound, and traditional neurological examination.     

Achievement motivation and its constructs: A cognitive model

The first section of this paper introduces a set of constructs, develops a cognitive model of motivation, and derives specific propositions for the case of achievement motivation. The model describes functional relationships among expectancies, instrumentalities, incentive values, and valences, each of which is calculated separately for situations, actions, and outcomes. Each valence is calculated with reference to an outcome's anticipated consequences, both immediate and delayed. The model draws on, but reworks and extends, Expectancy × Value Theory, Bolles' Psychological Syllogism, Instrumentality Theory, Achievement Motivation Theory, and Causal Attribution Theory. The second section examines the model's fit to the body of data that bears on a central area of research in achievement motivation, namely task preferences. The last section scrutinizes the motive construct as a summary concept and divides it into six parameter sets which represent sources of individual differences.I wish to thank Eric Klinger for a judicious translation of the paper into English which has considerably improved the original; Herbert Götzl, Uwe Kleinbeck, and Julius Kuhl for helpful comments; and Rosemarie Tweer for assistance in reanalyzing 31 studies on task preference.