Sensitivity of Fit Indices to Fake Perturbation of Ordinal Data: A Sample by Replacement Approach

In many psychological questionnaires the need to analyze empirical data raises the fundamental problem of possible fake or fraudulent observations in the data. This aspect is particularly relevant for researchers working on sensitive topics such as, for example, risky sexual behaviors and drug addictions. Our contribution presents a new probabilistic approach, called Sample Generation by Replacement (SGR), to address the problem of evaluating the sensitivity of 8 commonly used SEM-based fit indices (Goodness of Fit Index, GFI; Adjusted Goodness of Fit Index, AGFI; Expected Cross Validation Index, ECVI; Standardized Root-Mean-Square Residual Index, SRMR; Root-Mean-Square Error of Approximation, RMSEA; Comparative Fit Index, CFI; Nonnormed Fit Index, NNFI; and Normed Fit Index, NFI) to fake-good ordinal data. We used SGR to perform a simulation study involving 3 different SEM models, 2 sample size conditions, and 2 estimation methods: maximum likelihood (ML) and weighted least squares (WLS). Our results show that the incremental fit indices (CFI, NNFI, and NFI) are clearly more sensitive to fake perturbation than the absolute fit indices (GFI, AGFI, and ECVI). Overall, NFI turned out to be the best and most reliable fit index. We also applied SGR to real behavioral data on (non)compliance in liver transplant patients.     

Universality of the reversal transition in growth phenomena of molecular crystals

ABSTRACT

The fundamental origin of the reversal transition during crystal growth has been investigated by Monte Carlo simulations. Evidence is provided supporting the geometrical nature of the transition, arising from the broken translational invariance at the growth front and the interactions of multipoles of opposed parity. The range of interactions, the details of the force field and model are irrelevant to the occurrence and only determine the functional behaviour of the relevant physical quantities like the localisation of the critical point and the morphology of the phase diagram.     

What clocks tell us about the neural correlates of spatial imagery

We review a series of experimental studies aimed at answering some critical questions about the neural basis of spatial imagery. Our group used functional magnetic resonance imaging (fMRI) to explore the neural correlates of an online behaviourally controlled spatial imagery task without need for visual presentation—the mental clock task. Subjects are asked to imagine pairs of times that are presented acoustically and to judge at which of the two times the clock hands form the greater angle. The cortical activation elicited by this task was contrasted with that obtained during other visual, perceptual, verbal, and spatial imagery tasks in several block design studies. Moreover, our group performed an event‐related fMRI study on the clock task to investigate the representation of component cognitive processes in spatial imagery. The bulk of our findings demonstrates that cortical areas in the posterior parietal cortex (PPC), along the intraparietal sulcus, are robustly involved in spatial mental imagery and in other tasks requiring spatial transformations. PPC is bilaterally involved in different kinds of spatial judgement. Yet the degree to which right and left PPC are activated in different tasks is a function of task requirements. From event‐related fMRI data we obtained evidence that left and right PPC are activated asynchronously during the clock task and this could reflect their different functional role in subserving cognitive components of visuospatial imagery.     

Sample size, confidence, and contingency judgement.

According to statistical models, the acquisition function of contingency judgement is due to confidence increasing with sample size. According to associative models, the function reflects the accumulation of associative strength on which the judgement is based. Which view is right? Thirty university students assessed the relation between a fictitious medication and a symptom of skin discoloration in conditions that varied sample size (4, 6, 8 or 40 trials) and contingency (delta P = .20, .40, .60 or .80). Confidence was also collected. Contingency judgement was lower for smaller samples, while confidence level correlated inversely with sample size. This dissociation between contingency judgement and confidence contradicts the statistical perspective.     

Eye movements reveal mechanisms underlying attentional biases towards threat

Mechanisms underlying attentional biases towards threat (ABTs), such as attentional avoidance and difficulty of disengagement, are still unclear. To address this issue, we recorded participants' eye movements during a dot detection task in which threatening or neutral stimuli served as peripheral cues. We evaluated response times (RTs) in trials where participants looked at the central fixation cross (not at the cues), as they were required, and number and duration of (unwanted) fixations towards threatening or neutral cues; in all analyses trait anxiety was treated as a covariate. Difficulty in attentional disengagement (longer RTs) was found when peripheral threatening stimuli were presented for 100?ms. Moreover, we observed significantly shorter (unwanted) fixations on threatening than on neutral peripheral stimuli, compatible with an avoidance bias, for longer presentation times. These findings demonstrate that, independent of trait anxiety levels, disengagement bias occurs without eye movements, whereas eye movements are implied in threat avoidance.     

Political involvement moderates the impact of worldviews and values on SDO and RWA

The Dual Process Model (DPM) of social attitudes and prejudice proposes that Social Dominance Orientation (SDO) and Right Wing Authoritarianism (RWA) reflect two distinct motivational processes. In two studies, we investigated how political involvement moderates the impact of social worldviews and value‐based dimensions on SDO and RWA. We proposed that political involvement constrains SDO, RWA and their antecedents into a tighter left–right ideological dimension, therefore transforming the double dissociation pattern of the DPM into a double additive pattern. As expected, for stronger political involvement, Study 1 (N = 237) showed that SDO and RWA were a function of both the competitive jungle and the dangerous world worldviews, whereas Study 2 (N = 143) pointed out that SDO and RWA were both connected with the value dimensions of self‐enhancement and conservation.     

The role of familiarity in implicit memory effects: the case of exemplar activation

The present study investigates how person‐based representations stored in memory can influence subsequent information processing, depending upon subjective states during recollection of those representations. The experiment consisted of two phases. In the first phase, participants incidentally learned the gender category membership of various exemplars. Exemplars were presented in the form of forename–surname associations. In the second phase, the same surnames were used as primes in a name‐completion task. Results showed that the influence of the primes differed in relation to the exemplars' status in memory, as assessed by a recognition memory task. Only when the surnames looked familiar, but were not identifiable, an implicit effect of the exemplars' original category membership emerged, selectively influencing gender congruent name‐completions. Results are discussed in terms of attribution processes underlying the importance of the feelings of familiarity, and the need to devote more attention to the study of phenomenological factors in human memory. Copyright © 2000 John Wiley & Sons, Ltd.     

Whose hand is this? Differential responses of right and left extrastriate body areas to visual images of self and others’ hands

The extrastriate body area (EBA) is involved in perception of human bodies and nonfacial body parts, but its role in representing body identity is not clear. Here, we used on-line high-frequency repetitive transcranial magnetic stimulation (rTMS) to test the role of EBA in self–other distinction. In Experiments 1 and 2 we compared rTMS of right EBA with stimulation of left ventral premotor cortex (vPM), whereas in Experiment 3 we compared stimulation of right and left EBA. RTMS was applied during a hand laterality task in which self or others’ hand images were presented in first- versus third-person view (Experiments 1 and 3), or while participants had to explicitly recognize their own hands (Experiment 2) presented in first- versus third-person view. Experiment 1 showed that right EBA stimulation selectively speeded judgments on others’ hands, whereas no effect of left vPM stimulation was found. Experiment 2 did not reveal any effect of rTMS. Experiment 3 confirmed faster responses on others’ hands while stimulating right EBA and also showed an advantage when judging self with respect to others’ hands during stimulation of left EBA. These results would demonstrate that EBA responds to morphological features of human body contributing to identity processing.