Sensed presence as a correlate of sleep paralysis distress, social anxiety and waking state social imagery.

Isolated sleep paralysis (ISP) is a common parasomnia characterized by an inability to move or speak and often accompanied by hallucinations of a sensed presence nearby. Recent research has linked ISP, and sensed presence more particularly, with social anxiety and other psychopathologies. The present study used a large sample of respondents to an internet questionnaire (N=193) to test whether these associations are due to a general personality factor, affect distress, which is implicated in nightmare suffering and hypothesized to involve dysfunctional social imagery processes. A new measure, ISP distress, was examined in relation to features of ISP experiences, to self-reported psychopathological diagnosis, to scores on the Leibowitz Social Anxiety Scale and to scores on a new questionnaire subscale assessing social imagery in a variety of waking states. Three main results were found: (1) ISP experiences are only weakly associated with a prior diagnosis of mental disorder, (2) sensed presence during ISP is associated preferentially with ISP distress, and (3) ISP distress is associated with dysfunctional social imagery. A general predisposition to affective distress may influence the distress associated with ISP experiences; overly passive social imagery may, in turn, be implicated in this affect distress influence.

An information theory analysis of visual complexity and dissimilarity.

The subjective complexity of a computer-generated bitmap image can be measured by magnitude estimation scaling, and its objective complexity can be measured by its compressed file size. There is a high correlation between these measures of subjective and objective complexity over a large set of marine electronic chart and radar images. The subjective dissimilarity of a pair of bitmap images can be predicted from subjective and objective measures of the complexity of each image, and from the subjective and objective complexity of the image produced by overlaying the two simple images. In addition, the subjective complexity of the image produced by overlaying two simple images can be predicted from the subjective complexity of the simple images and the subjective dissimilarity of the image pair. The results of the experiments that generated these complexity and dissimilarity judgments are consistent with a theory, outlined here, that treats objective and subjective measures of image complexity and dissimilarity as vectors in Euclidean space.

Variety and intensity of emotions in nightmares and bad dreams.

Nightmares are usually defined as frightening dreams that awaken the sleeper. This study uses the waking criterion to distinguish between nightmares and bad dreams and investigated the variety and intensity of emotions reported in each form of disturbing dream. Ninety participants recorded their dreams for 4 consecutive weeks and, for each dream recalled, noted the emotions present and their intensities on a 9-point scale. Thirty-six participants reported at least one nightmare and one bad dream over the 4 weeks covered by the log, while 29 reported having had at least one bad dream but no nightmares. Nightmares were rated as being significantly (p < 0.001) more intense than bad dreams. Thirty percent of nightmares and 51% of bad dreams contained primary emotions other than fear. The findings support the claim that awakening can serve as an indirect measure of nightmare intensity and raise important implications for the operational definition of nightmares.

Visual complexity: a review.

The idea of visual complexity, the history of its measurement, and its implications for behavior are reviewed, starting with structuralism and Gestalt psychology at the beginning of the 20th century and ending with visual complexity theory, perceptual learning theory, and neural circuit theory at the beginning of the 21st. Evidence is drawn from research on single forms, form and texture arrays and visual displays. Form complexity and form probability are shown to be linked through their reciprocal relationship in complexity theory, which is in turn shown to be consistent with recent developments in perceptual learning and neural circuit theory. Directions for further research are suggested.