Instability of hierarchical cluster analysis due to input order of the data: the PermuCLUSTER solution

Hierarchical agglomerative cluster analysis (HACA) may yield different solutions under permutations of the input order of the data. This instability is caused by ties, either in the initial proximity matrix or arising during agglomeration. The authors recommend to repeat the analysis on a large number of random permutations of the rows and columns of the proximity matrix and select a solution with the highest goodness-of-fit. This approach was implemented in an SPSS add-in, PermuCLUSTER, which can perform all HACA methods of SPSS. Analyses of 2 data sets show that (a) results are affected by input order, (b) instability in one method co-occurs with instability in other methods, and (c) some instability effects are more dramatic because they occur at higher agglomeration levels.     

Mood-congruent attentional bias in dysphoria: maintained attention to and impaired disengagement from negative information

Attentional bias to negative information has been proposed to be a cognitive vulnerability factor for the development of depression. In 2 experiments, the authors examined mood-congruent attentional bias in dysphoria. In both experiments, dysphoric and nondysphoric participants performed an attentional task with negative, positive, and neutral word cues preceding a target. Targets appeared either at the same or at the opposite location of the cue. Overall, results indicate that dysphoric participants show maintained attention for negative words at longer stimulus presentations, which is probably caused by impaired attentional disengagement from negative words. Furthermore, nondysphoric participants maintain their attention more strongly to positive words. These results are discussed in relation to recent developments in the pathogenesis and treatment of depression.     

Bottom-up and top-down control in visual search

Previous research suggests that the allocation of attention is largely controlled either in a stimulus-driven or in a goal-driven manner. To date, few studies have systematically manipulated variables affecting stimulus-driven and goal-driven selection independently in order to investigate how both manners of control interrelate and affect performance in visual search. In the present study observers were presented with search displays consisting of an array of line segments rotated at various orientations. The task of observers was to indicate the presence or absence of a vertical line segment (the target) presented amongst a series of nontargets and possibly one distractor. By varying the absolute differences in orientation between the target, nontargets, and distractors, relative target-distractor salience and target-distractor similarity were independently manipulated to investigate the contribution of stimulus-driven and goal-driven control. The major result was that relative target-distractor salience and target-distractor similarity affected search performance independently. Performance was better in cases where the irrelevant distractor was not a salient item in the search display and did not look similar to the target. The results are discussed in terms of models of attentional control.     

Cultivating expertise in informal reasoning.

People generally develop some degree of competence in general informal reasoning and argument skills, but how do they go beyond this to attain higher expertise? Ericsson has proposed that high-level expertise in a variety of domains is cultivated through a specific type of practice, referred to as "deliberate practice." Applying this framework yields the empirical hypothesis that high-level expertise in informal reasoning is the outcome of extensive, deliberate practice. This paper reports results from two studies evaluating the hypothesis. University student participants completed 12 weeks of deliberate practice in informal reasoning. Quantity of practice was recorded by computer, and additionally assessed via self-report. The hypothesis was supported: Students in both studies showed a large improvement, and practice, as measured by computer, was related to amount of improvement in informal reasoning. These findings support adopting a deliberate practice approach when attempting to teach or learn expertise in informal reasoning.     

Switching between spatial stimulus-response mappings: a developmental study of cognitive flexibility

Four different age groups (8-9-year-olds, 11-12-year-olds, 13-15-year-olds and young adults) performed a spatial rule-switch task in which the sorting rule had to be detected on the basis of feedback or on the basis of switch cues. Performance errors were examined on the basis of a recently introduced method of error scoring for the Wisconsin Card Sorting Task (WCST; Barcelo & Knight, 2002). This method allowed us to differentiate between errors due to failure-to-maintain-set (distraction errors) and errors due to failure-to-switch-set (perseverative errors). The anticipated age differences in performance errors were most pronounced for perseverative errors between 8-9 years and 11-12 years, but for distraction errors adult levels were not reached until 13-15 years. These findings were interpreted to support the notion that set switching and set maintenance follow distinct developmental trajectories.     

Does imminent threat capture and hold attention?

According to models of attention and emotion, threat captures and holds attention. In behavioral tasks, robust evidence has been found for attentional holding but not for attentional capture by threat. An important explanation for the absence of attentional capture effects is that the visual stimuli used posed no genuine threat. The present study investigated whether visual cues that signal an aversive white noise can elicit attentional capture and holding effects. Cues presented in an attentional task were simultaneously provided with a threat value through an aversive conditioning procedure. Response latencies showed that threatening cues captured and held attention. These results support recent views on attention to threat, proposing that imminent threat captures attention in everyone.     

Gender and culture differences in emotion

In this article, the authors report a secondary analysis on a cross-cultural dataset on gender differences in 6 emotions, collected in 37 countries all over the world. The aim was to test the universality of the gender-specific pattern found in studies with Western respondents, namely that men report more powerful emotions (e.g., anger), whereas women report more powerless emotions (e.g., sadness, fear). The authors expected the strength of these gender differences to depend on women's status and roles in their respective countries, as operationalized by the Gender Empowerment Measure (GEM; United Nations Development Programme Human Development Report 2002). Overall, the gender-specific pattern of women reporting to experience and express more powerless emotions and men more powerful emotions was replicated, and only some interactions with the GEM were found.     

Work group diversity and group performance: an integrative model and research agenda

Research on the relationship between work group diversity and performance has yielded inconsistent results. To address this problem, the authors propose the categorization-elaboration model (CEM), which reconceptualizes and integrates information/decision making and social categorization perspectives on work-group diversity and performance. The CEM incorporates mediator and moderator variables that typically have been ignored in diversity research and incorporates the view that information/decision making and social categorization processes interact such that intergroup biases flowing from social categorization disrupt the elaboration (in-depth processing) of task-relevant information and perspectives. In addition, the authors propose that attempts to link the positive and negative effects of diversity to specific types of diversity should be abandoned in favor of the assumption that all dimensions of diversity may have positive as well as negative effects. The ways in which these propositions may set the agenda for future research in diversity are discussed.