Linking dynamical perceptual decisions at different levels of description in motion pattern formation: computational simulations

A two-level dynamical model of motion pattern formation is developed in which local motion/ nonmotion perceptual decisions are based on inhibitory competition between area V1 detectors responsive to motion-specifying versus motion-independent stimulus information, and pattern-level perceptual decisions are based on inhibitory competition between area MT motion detectors with orthogonal directional selectivity. The model accounts for the effects of luminance perturbations on the relative size of the pattern-level hysteresis effects reported by Hock and Ploeger (2006) and also accounts for related experimental results reported by Hock, Kelso, and Sch?ner (1993). Single-trial simulations demonstrated the crucial role of local motion/nonmotion bistability and activation-dependent future-shaping interactions in stabilizing perceived global motion patterns. Such interactions maintain currently perceived motion patterns by inhibiting the soon-to-be-stimulated motion detectors that otherwise would be the basis for the perception of an alternative pattern.     

Use of temperature variations to combat drivers' drowsiness

The purpose of the present study was to evaluate the efficiency of temperature variations as a measure against drivers' drowsiness. A system for regulation of the air temperature in the cab was installed in two trucks. Irregular temperature reductions of about 8 degrees C were introduced. The periods between the temperature reductions varied among 5, 6, 7, and 8 min. The periods for the temperature reductions varied between 2, 4, 6, and 8 min. The system was tested with 6 drivers on 54 trips. The system was applied for periods varying between 30 to 300 min. Changes in wakefulness were analysed using subjective ratings by the lorry drivers. The application of the system significantly improved subjectively rated wakefulness. The wakefulness was rated with a questionnaire completed after 10 min. use of a cooling system and at the end of its use. Analysis showed individual differences in the usefulness of the system: 3 of the 6 truck drivers reported positive reactions to the use of the temperature cooling system.     

Implicit and explicit attitudes toward high-fat foods in obesity

This study examined implicit and explicit attitudes toward high-fat foods in obese (n = 30) and normal-weight controls (n = 31). The Implicit Association Test (A. G. Greenwald, D. E. McGee, & J. L. K. Schwartz, 1998) was used to measure the differential association of the 2 target categories--high-fat vs. low-fat food words--with an attribute dimension (positive vs. negative). Results suggest that obese people are characterized by a significantly stronger implicit negative attitude toward high-fat foods than are normal-weight controls. This implicit negative attitude is contradictory to their preferences and behavior: Several studies indicate that obese people prefer and consume high-fat foods. Apparently, obese people like the taste of high-fat foods but not the fat content itself, not only on the explicit but also on the implicit level.     

Characterizing the ADHD phenotype for genetic studies

The genetic study of ADHD has made considerable progress. Further developments in the field will be reliant in part on identifying the most appropriate phenotypes for genetic analysis. The use of both categorical and dimensional measures of symptoms related to ADHD has been productive. The use of multiple reporters is a valuable feature of the characterization of psychopathology in children. It is argued that the use of aggregated measures to characterize the ADHD phenotype, particularly to establish its pervasiveness, is desirable. The recognition of the multiple comorbidities of ADHD can help to isolate more specific genetic influences. In relation to both reading disability and conduct disorder there is evidence that genes may be involved in the comorbid condition that are different from pure ADHD. To date, progress with the investigation of endophenotypes for ADHD has been disappointing. It is suggested that extending such studies beyond cognitive underpinnings to include physiological and metabolic markers might facilitate progress.     

Effect of prefrontal cortex damage on resolving lexical ambiguity in text

The function of suppression of context-inappropriate meanings during lexical ambiguity resolution was examined in 25 adults with prefrontal cortex damage (PFCD) localized to the left (N=8), right (N=6), or bilaterally (N=11); and 21 matched Controls. Results revealed unexpected inverse patterns of suppression between PFCD and Control groups, with measures suggesting decreased interference across time in the PFCD group and increased interference in the Control group. The PFCD group, however, had significantly lower accuracy rates for the context-inappropriate condition. Results suggest a loss of the control aspects of inhibitory processes in lexical ambiguity resolution following PFCD. An aging effect on suppression function is also suggested.     

Overgeneral memory and suppression of trauma memories in post-traumatic stress disorder

The study investigated the relationship between the suppression of trauma memories and overgeneral memory in 42 assault survivors with and without PTSD. Overgeneral memory (OGM) was assessed with a standard autobiographical memory test (AMT). Participants completed two further AMTs under the instructions to either suppress or not suppress assault memories, in counterbalanced order. Participants with PTSD retrieved fewer and more general memories when following the suppression instruction than participants without PTSD, but not under the control instruction. OGM correlated with PTSD symptom severity, and measures of cognitive avoidance. The results are discussed with reference to current theories of overgeneral memory and its possible relationship with PTSD.     

Nice wor_ if you can get the wor_: subliminal semantic and form priming in fragment completion

Two experiments investigated subliminal semantic and form priming in a word-completion task. Visual gap-words with a dominant and a subordinate solution were preceded by form-related or by semantically related words, which were briefly presented and sandwich-masked. Priming of the subordinate solution was assessed in Experiment 1, relative to a neutral condition. Both solutions were primed in Experiment 2. In the absence of conscious prime recognition, both semantic and form primes reliably increased the probability with which the primed solution was given. With our variant of fragment-completion, response priming can be ruled out as explanation. Moreover, effects were already present at first presentation, excluding an interpretation in terms of partial awareness due to massive repetition. The data demonstrate automatic activation at both form and semantic levels in the absence of conscious awareness.     

Stability of nonlinear principal components analysis: an empirical study using the balanced bootstrap

Principal components analysis (PCA) is used to explore the structure of data sets containing linearly related numeric variables. Alternatively, nonlinear PCA can handle possibly nonlinearly related numeric as well as nonnumeric variables. For linear PCA, the stability of its solution can be established under the assumption of multivariate normality. For nonlinear PCA, however, standard options for establishing stability are not provided. The authors use the nonparametric bootstrap procedure to assess the stability of nonlinear PCA results, applied to empirical data. They use confidence intervals for the variable transformations and confidence ellipses for the eigenvalues, the component loadings, and the person scores. They discuss the balanced version of the bootstrap, bias estimation, and Procrustes rotation. To provide a benchmark, the same bootstrap procedure is applied to linear PCA on the same data. On the basis of the results, the authors advise using at least 1,000 bootstrap samples, using Procrustes rotation on the bootstrap results, examining the bootstrap distributions along with the confidence regions, and merging categories with small marginal frequencies to reduce the variance of the bootstrap results.