Nonlinear principal components analysis: introduction and application

The authors provide a didactic treatment of nonlinear (categorical) principal components analysis (PCA). This method is the nonlinear equivalent of standard PCA and reduces the observed variables to a number of uncorrelated principal components. The most important advantages of nonlinear over linear PCA are that it incorporates nominal and ordinal variables and that it can handle and discover nonlinear relationships between variables. Also, nonlinear PCA can deal with variables at their appropriate measurement level; for example, it can treat Likert-type scales ordinally instead of numerically. Every observed value of a variable can be referred to as a category. While performing PCA, nonlinear PCA converts every category to a numeric value, in accordance with the variable's analysis level, using optimal quantification. The authors discuss how optimal quantification is carried out, what analysis levels are, which decisions have to be made when applying nonlinear PCA, and how the results can be interpreted. The strengths and limitations of the method are discussed. An example applying nonlinear PCA to empirical data using the program CATPCA (J. J. Meulman, W. J. Heiser, & SPSS, 2004) is provided.     

Confidence intervals for gamma-family measures of ordinal association

This research focused on confidence intervals (CIs) for 10 measures of monotonic association between ordinal variables. Standard errors (SEs) were also reviewed because more than 1 formula was available per index. For 5 indices, an element of the formula used to compute an SE is given that is apparently new. CIs computed with different SEs were compared in simulations with small samples (N = 25, 50, 75, or 100) for variables with 4 or 5 categories. With N > 25, many CIs performed well. Performance was best for consistent CIs due to N. Cliff and colleagues (N. Cliff, 1996; N. Cliff & V. Charlin, 1991; J. D. Long & N. Cliff, 1997). CIs for Spearman's rank correlation were also examined: Parameter coverage was erratic and sometimes egregiously underestimated.     

Predictors of disclosure of human immunovirus-positive serostatus among Latino gay men

To test a theoretical approach to disclosure of human immunovirus (HIV) status, 301 HIV-positive Latino gay men were interviewed using Audio-CASI (Computer Assisted Self-Interview technology with Audio enhancement). Consequence theory and social influence theory were combined to create a model of antecedents of disclosure. Results provided support for both theories. Perceived positive consequences were associated with greater disclosure to casual partners, families, and friends, whereas perceived negative consequences were associated with less disclosure to friends and family members. Social influence of peer behavioral norms was predictive of disclosure to all three target groups. Gay community social influence produced different effects on disclosure of HIV-positive status: a negative association for casual partners, a positive association for close friends, and no relationship for family members. Time since diagnosis was also predictive of disclosure.     

How Social Are Task Representations?

ABSTRACT— The classical Simon effect shows that actions are carried out faster if they spatially correspond to the stimulus signaling them. Recent studies revealed that this is the case even when the two actions are carried out by different people; this finding has been taken to imply that task representations are socially shared. In work described here, we found that the "interactive" Simon effect occurs only if actor and coactor are involved in a positive relationship (induced by a friendly-acting, cooperative confederate), but not if they are involved in a negative relationship (induced by an intimidating, competitive confederate). This result suggests that agents can represent self-generated and other-generated actions separately, but tend to relate or integrate these representations if the personal relationship between self and other has a positive valence.     

Establishing Derived Manding for Specific Amounts with Three Children: An Attempt at Synthesizing Skinner’s Verbal Behavior with Relational Frame Theory

The Psychological Record - Participants were 2 typically developing children, aged 9 and 10 years, and 1 child, aged 4 years, with a reported severe speech delay. Five specific mand functions were...     

A behavioral route to dysfunctional representations: The effects of training approach or avoidance tendencies towards novel animals in children

We examined the effects of training to approach or avoid novel animals on fear-related responses in children. Ninety-five primary school children (9-13 years old) were instructed to repeatedly push away or pull closer pictures of novel animals. We tested whether this manipulation would lead to changes in self-reported attitudes, implicit attitudes, fear beliefs, and avoidance behaviors towards these animals.The training produced more positive self-reported attitudes towards the pulled animal and more negative attitudes towards the pushed animal. After the training, girls reported more fear and avoidance of the pushed animal than of the pulled animal, while such training effects were absent in boys. No significant training effects were observed on implicit attitudes. Interestingly, the level of anxiety disorder symptoms prior to training was related to some of the training effects: Stronger prior fear was related to stronger changes in self-reported attitudes, and in boys, also to fear beliefs.The finding that a simple approach-avoidance training influences children's fear-related responses lends support to general theories of fear acquisition in children as well as to models that try to explain the intergenerational transmission of anxiety. [184 words]     

Development and Initial Validation of an Abbreviated Spider Phobia Questionnaire Using Item Response Theory

An abbreviated Spider Phobia Questionnaire (SPQ) was developed using methods based in item response theory. Fifteen of the 31 SPQ items that demonstrated good to excellent discrimination along the spider fear continuum were retained in Study 1 that consisted of 1,555 nonclinical and clinical participants. The SPQ-15 demonstrated good internal consistency and correlated highly with the full SPQ. Structural equation modeling revealed that the SPQ-15 demonstrated excellent convergent validity, with strong associations with small animal disgust and other phobic symptoms. Supportive evidence was also found for divergent validity in relation to panic-related symptoms. The SPQ-15 was uniquely predictive of avoidance behavior and fear and disgust responding towards spiders in nonclinical, analogue, and treatment-seeking samples in Studies 2, 3, and 4. Lastly, in Study 5, the SPQ-15 was sensitive to the effects of exposure-based treatment. These findings suggest that the SPQ-15 has considerable strengths, including decreased assessment and scoring time while retaining high reliability, validity, and sensitivity.     

Expectancy bias and the persistence of posttraumatic stress

Anxious individuals tend to overestimate the probability that encounters with anxiogenic stimuli (CS) will be followed by aversive consequences (UCS). This study examined whether such (biased) UCS expectancies predict the persistence of PTSD symptoms. A total of 265 soldiers were recruited before a four-month deployment to Iraq in 2004. About 2-5 months after deployment, 171 (65%) soldiers completed self-report scales about adverse events in Iraq and PTSD symptoms, and a UCS expectancy task. In this task, participants were exposed to a series of deployment-related and deployment-unrelated (control) picture stimuli. For each trial, the participants indicated the subjective probability that a particular slide would be followed by an imminent loud noise. Around 15 months after deployment, 130 (76%) soldiers completed surveys about PTSD symptoms again. Only a small group of participants had high levels of PTSD symptoms. Regression analyses showed that the level of PTSD symptoms at 15 months was predicted by earlier PTSD symptoms, but also and independently by an enhanced UCS expectancy to deployment-related stimuli. The findings support the notion that UCS expectancy bias contributes to the persistence of PTSD symptoms.     

Uncertainty about perception and dissociation after compulsive-like staring: Time course of effects

Repeated and compulsive-like checking reduces confidence in memory for the last check. Obsessive-compulsive (OC) patients are not only uncertain about memory, but may also be uncertain about perception, while this perceptual uncertainty may be associated with prolonged visual fixation on the object of uncertainty. It was reported earlier that, among healthy participants, prolonged staring at light bulbs or gas rings induces OC-like uncertainty about perception and feelings of dissociation [van den Hout, M. A., Engelhard, I. M., de Boer, C., du Bois, A., & Dek, E. (2008). Perseverative and compulsive-like staring causes uncertainty about perception. Behaviour Research and Therapy, 46, 1300–1304]. In that study, staring continued for 10 min. For patients, however, staring intervals seem to be considerably shorter. To test the clinical credibility of the paradigm as a model of the maintenance of OC perceptual uncertainty, we investigated whether the effects of staring materialize long before 10 min. Five groups of 16 undergraduates participated: one group did not stare at a gas stove while the others stared for 7.5, 15, 30 or 300 s. In the absence of staring, no pre-to-post increase in dissociation/uncertainty was reported, but after staring it was. The larger part of the observed dissociation/uncertainty after 5 min had occurred within 30 s, and around 50% of this maximal increase was reported between 7.5 and 15 s. Thus, even relatively short intervals of staring induce uncertainty about perception and dissociative experiences. Perseverative looking at objects may be a counter-productive OC strategy, which increases uncertainty about perception and may serve to maintain the disorder.