The illusion of transparency and chromatic subjective contours

Subjective contours can be produced that include an illusion of edge and an extension of color throughout the area of the illusion. The phenomenological appearance is of a transparent colored shape in front of the background. Two explanations of this illusion are proposed. The first is that there is an assimilation of color analogous to brightness assimilation. The second is a variant of the stratification of depth theory of subjective contours. In it, the pattern elements lead to the illusion of a surface in front of the pattern elements. We thus predicted that an illusion of transparency would enhance the subjective contour, Metelli’s model of transparency was used to quantify our prediction, and it was found that the possibility of transparency was a powerful predictor of the chromatic subjective contour.     

The subliminal perception of movement and the course of autokinesis

The course of autokinesis is shown to be sensitive to the real movement of a surrounding stimulus. With the supraliminal presentation of this stimulus, apparent movement in a direction opposite to that of the real movement is induced. With the subliminal presentation of the same stimulus the real movement serves to inhibit autokinesis by inducing brief periods of stationarity between the phases of upward and downward apparent movement. The results confirm previous findings that the movement of a stimulus may be discriminated without there being any perceptual (phenomenal) adjunct.     

Effects of spatial-frequency specific adaptation and target duration on visual persistence

Two experiments investigated the properties of visual persistence as functions of spatial frequency, stimulus duration, and pattern-specific adaptation. In Experiment 1, increasing the duration of high spatial-frequency gratings from 50 to 500 msec decreased the duration of visual persistence produced by that grating to an asymptotic level. However, low-frequency gratings produced a constant estimate of visual persistence independent of presentation time. Also, spatial-frequency specific adaptation reduced the persistence of the high-frequency gratings to this asymptotic level, but the lower frequency persistence estimates already at this level were unaffected (Experiment 2). These findings are related to possible temporal properties of the sustained and transient visual systems.     

Some aspects of the management of patients with epilepsy in pregnancy

The care of pregnant epileptics calls for a high measure of personal attention and material expenditure. Above all, it means close cooperation between the epileptic specialist, the obstetrician, and the clinical pharmacologist. The need for this collaboration, and its effectiveness, are demonstrated by means of practical examples, with special consideration of blood level.     

Perception of artificial stereoscopic stimuli from an incorrect viewing point

The present study investigates the distortions in the perception of artificial stereoscopic displays seen from an inappropriate distance and/or orientation. Stereoscopic displays represent 3-D information correctly, provided they are seen from the correct station point. The viewing point may differ from the correct station point in its distance or in its orientation to the screen. These differences lead to distortions that can be predicted mathematically. However, the perceptual function may be different from the predictions, since people may possibly compensate for the distortions. To test the degree of this compensation, participants saw anaglyphic stereoscopic stimuli that showed angles in the horizontal plane, and their perception of the configuration was tested for various orientations and distances. The estimates were compared with the values predicted from the mathematical functions, and participants' virtual positions were reconstructed via nonlinear regressions. The analyses revealed a moderate compensation for viewing orientations and a systematically overestimation of the viewing distances. These results indicate that people compensate partially for distortions in stereopsis, given that the relevant information is available.     

Two-year stability of Psychosis Proneness Scales and their relations to personality disorder traits

Two-year stability of Physical Anhedonia (PhA), Perceptual Aberration (PER), and Magical Ideation (MI) scale scores and their relation to personality disorder traits were examined. Additionally, the effects of a time-lagged (prospective) versus concurrent measurement of psychosis proneness and personality disorder traits were studied to examine the specificity of MI, PER, and PhA. With a non-college-student sample (n = 404), stability for PhA was sufficiently high, but for PER and MI, stability was moderate to low. The correlations between personality disorder traits and psychosis proneness scales demonstrate that simultaneous assessment leads to a more nonspecific pattern of associations for MI and PER, although the correlation to schizotypal personality disorder traits were the highest. However, prospectively only MI, but neither PER nor PhA, emerged as a significant predictor for schizotypal and paranoid personality disorder traits in multiple-regression analysis. This suggests that MI may allow for a more specific assessment of psychosis proneness than PER.     

A theory of lexical access in speech production

Preparing words in speech production is normally a fast and accurate process. We generate them two or three per second in fluent conversation; and overtly naming a clear picture of an object can easily be initiated within 600 msec after picture onset. The underlying process, however, is exceedingly complex. The theory reviewed in this target article analyzes this process as staged and feed-forward. After a first stage of conceptual preparation, word generation proceeds through lexical selection, morphological and phonological encoding, phonetic encoding, and articulation itself. In addition, the speaker exerts some degree of output control, by monitoring of self-produced internal and overt speech. The core of the theory, ranging from lexical selection to the initiation of phonetic encoding, is captured in a computational model, called WEAVER++. Both the theory and the computational model have been developed in interaction with reaction time experiments, particularly in picture naming or related word production paradigms, with the aim of accounting for the real-time processing in normal word production. A comprehensive review of theory, model, and experiments is presented. The model can handle some of the main observations in the domain of speech errors (the major empirical domain for most other theories of lexical access), and the theory opens new ways of approaching the cerebral organization of speech production by way of high-temporal-resolution imaging.     

Coping with a Paraphrenic World in Late Life

This study deals with late paraphrenia from a psychological coping perspective. Analyses of coping behavior in relation to paraphrenic delusions and hallucinations revealed rational choices of coping efforts and generally consistent emotional reactions to the subjectively perceived problem. The majority of the patients did not display evidence of premorbid abnormal personalities or life courses. The creation and sustainment of psychotic thoughts are discussed in relation to lack of correcting social feedback due to social isolation and weakened cognitive source monitoring. The implications of a psychological coping perspective for intervention are indicated.