Inferring the structure of latent class

Present optimization techniques in latent class analysis apply the expectation maximization algorithm or the Newton-Raphson algorithm for optimizing the parameter values of a prespecified model. These techniques can be used to find maximum likelihood estimates of the parameters, given the specified structure of the model, which is defined by the number of classes and, possibly, fixation and equality constraints. The model structure is usually chosen on theoretical grounds. A large variety of structurally different latent class models can be compared using goodness-of-fit indices of the chi-square family, Akaike’s information criterion, the Bayesian information criterion, and various other statistics. However, finding the optimal structure for a given goodness-of-fit index often requires a lengthy search in which all kinds of model structures are tested. Moreover, solutions may depend on the choice of initial values for the parameters. This article presents a new method by which one can simultaneously infer the model structure from the data and optimize the parameter values. The method consists of a genetic algorithm in which any goodness-of-fit index can be used as a fitness criterion. In a number of test cases in which data sets from the literature were used, it is shown that this method provides models that fit equally well as or better than the models suggested in the original articles.     

Developmental changes in facial expressions of emotions in the strange situation during the second year of life

Infants' expressions of discrete emotions were coded during the more stressful episodes (4 through 8) of the Strange Situation at 13 and 18 months. The data showed a significant decrease in full-face expressions (more complex configurations of movements) and a significant increase in component expressions (simpler and more constrained patterns of movements). The authors interpreted this trend as a developmental change toward more regulated and less intense emotions. Consistent with this view, the aggregate index of infants' full-face negative emotion expressions, interpreted as reflecting relatively unregulated intense emotions, correlated significantly with maternal ratings of difficult temperament. The authors discuss alternative interpretations of the findings in terms of changes in reactivity/arousability and the emerging capacity for self-regulation.     

What response times tell of children's behavior on the balance scale task

Analysis of accuracy of responses to balance scale problems gives a global idea of the cognitive processes that underlie problem-solving behavior on this task. We show that response times (RTs) provide additional detailed information about the kind and duration of these processes. We derive predictions about the RTs from Siegler's (1981) model for the balance scale task, including the counterintuitive prediction that young adults are slower than children in solving particular balance scale problems. The predictions were tested in a study in which 191 6- to 22-year-old participants were presented with a computerized balance scale task. RTs were analyzed with regression models. In addition to qualitative differences between items, we also modeled quantitative differences between items in the regression models. Analyses supported the predictions and provided additional knowledge on the rules. Rule II was reformulated as a rule that always involves the encoding, but not always the correct application of the distance cue. RTs provided evidence for the use of a buggy-rule and not an addition-rule. Finally, a relation between rule inconsistency and increased RT was found.     

Differential effects of emotional arousal in short- and long-term memory in healthy adults

Recent studies demonstrated important differences between short- and long-term memory mechanisms. Besides, the emotional component has a crucial role in memory formation. This study was carried out to answer whether there is a differential influence of emotional arousal in short- and long-term memory in healthy adults. Thirty-one healthy volunteers were divided into two major groups. In the first group long-term memory (LTM) was evaluated, with the testing session one week after training. The second group was tested 1h after training, where short-term memory (STM) was evaluated. Each group was divided in to two subgroups. One half of the volunteers was exposed to an emotionally neutral story, and the other half of each group was exposed to a closely matched but more emotionally arousing story. The testing session consisted of a questionary containing 80 questions of multiple choices. The results were evaluated through percentage of correct answers. Results showed that correct answers were increased, in LTM measures, in the subjects that were given the emotional version of the test. In STM measures, no differences were found between the emotional and neutral version. However, the presentation of emotional story caused an emotional reaction in both groups. The lack of effect of emotional arousal in STM suggests that amygdala is not related to STM mechanisms. Further studies using different approaches are needed to elucidate if STM processes are influenced by emotional arousal.     

Children as carers: the impact of parental illness and disability on children's caring roles

The nature and extent of young caring in the UK continue to be a feature of a growing number of research programmes motivated by a children and carers' rights philosophy. However, the context in which young caring occurs as a result of parental ill-health or disability can only be fully understood by examining the findings and implications of medical research into parental impairment, and the social movements that have served to re-define the concept of 'disability' in society. This paper examines the arguments put forward by medical researchers, by those proposing a social model of disability and by those who have specifically investigated the conditions and experiences of young carers. It argues that children's caring roles within families where there is parental illness or disability need to be understood not only as a reflection of the nature of the medical condition itself, but as a consequence of complex family, social and economic processes. A 'whole family' approach is proposed, where the needs of children and parents are respected and responded to.     

对人眼色觉异常的定量测量研究

依据Ｒａｙｌｅｉｇｈ颜色匹配方法研制人眼颜色视觉定量测量实验装置,并对２０名色觉正常和３０名色觉异常大学生的颜色视觉进行测量。结果表明,色觉异常被试在Ｒａｙｌｅｉｇｈ匹配中点和匹配范围测量值上均与色觉正常被试者存在明显的差异。     

FOK判断等级及其准确性的实验研究

通过实验集中探讨了FOK判断等级及其准确性的影响因素。实验以中文字串为学习材料,使用组内设计的实验方法研究了被激活信息的量和强度对FOK等级及准确性的影响。实验结果表明：FOK判断的等级是由被激活信息的总量决定的,和被激活信息的正确与否无关;FOK判断的准确性是由被激活信息的强度决定的;且二者之间是有内在联系的。