Vicario's illusion of sloping steps reexamined

If a few parallel horizontal rows of dots are set diagonally, like steps, across the visual field, the inner rows appear not to be horizontal but sloping up to one side; the effect holds as long as the vertical distances between the rows do not exceed a given visual angle. This illusion, described by Vicario in 1978, was never explained. An experiment is reported in which the illusion was still visible at row separations well in excess of the spatial limits originally considered, provided the stimulus elements were enlarged. The maximum illusion was obtained for length ratios (interrow distance to size of dots) identical to those which have been shown to produce the largest effects in a number of illusions of area and length. This suggests that Vicario's illusion is similar to other illusions of extent, and that it can be explained by a neural extent-coding model.     

Motion aftereffects with rotating ellipses

Summary The perceptual outcome and the motion-aftereffect duration generated by the rotation on the frontal plane of an ellipse with a bar depend on whether the bar is placed along the major or the minor axis. When the bar is placed along the minor axis, a stereokinetic transformation occurs, and the pattern looks like a tilting ring with a perpendicular bar moving rigidly with it. Placing the bar along the major axis prevents the stereokinetic transformation: subjects report deformations and relative motion of the bar with respect to the ellipse. We found that motion aftereffects last longer when the bar is placed along the minor rather than along the major axis. A series of experiments was carried out to investigate whether differences in aftereffect duration are related to the stereokinetic transformation. Results seem to suggest that they are not.The authors' names are in alphabetical order.     

Stereokinesis with moving visual phantoms

When a flat pattern composed of a solid ellipse with two symmetrical semirings (corresponding to the visible parts of a contour ellipse whose major axis is perpendicular to that of the solid ellipse) is slowly rotated in the frontoparallel plane, a compelling three-dimensional impression occurs. Subjects report seeing an egg-shaped object that is inserted into a circular ring: the two objects move solidly into three-dimensional space and a moving visual phantom is generated so that the ring appears completed by an illusory curved bar in the region closest to the observer during rotation. A number of variations of this illusion are presented. It is shown that stereokinetic phantoms (i) maintain the shape of the inducing elements; (ii) appear only after the stereokinetic transformation has taken place; and (iii) depend on the organization of the three-dimensional percept as a whole. Relations between stereokinetic phantoms and other completion phenomena are presented and discussed.     

Revisitation of the luminance conditions for the occurrence of the achromatic neon color spreading illusion

This paper develops the idea (Bressan, 1993) that neon spreading derives from the perceptual scissioning of ordinary assimilation color, a process identical to that occurring with nonillusory colors in phenomenal transparency. It is commonly held that the critical elements in achromatic neon spreading patterns must be of luminance intermediate between that of the embedding lines and of the background. The interpretation of neon spreading on the basis of color scissioning, however, predicts that neon spreading should also be observed for different luminance hierarchies, provided that these are compatible with transparency. This prediction found experimental support in the present work. The results suggest that (1) the widespread notion that chromatic and achromatic neon spreading must be mediated by separate mechanisms is unwarranted; (2) the widespread notion that color spreading in ordinary assimilation patterns and color spreading in neon patterns must be mediated by separate mechanisms is unwarranted; and (3) other than pointing to the way in which the overall organization of a scene affects the mode of color appearance, the neon spreading effect may not convey any extra theoretical relevance.     

A prescriptive paradigm for sequencing instruction in physical education

Recent advances in the understanding of the neurological basis of motor control have made possible an explanation of motor skill acquisition in terms of the notion of programs of muscle synergies. The progressive development of an individual's capacity to control these synergies may be presented as a kind of hierarchical organization of processing levels based upon changes in the neurological location of motor control and the ability of the individual to make adjustments in the programs. This paper is an attempt to apply this information about the processing levels of motor control to the problem of the identification of a paradigm to assist practitioners in the design of sequences of motor skill learning experiences. Such a paradigm is proposed as a reformulation of Jewett's Movement Process Category System, a model originally created for use in curriculum decision-making.The proposed reformulation identifies three subphases of adaptive skill acquisition: skill construction, where a program of synergies is first automated; skill stabilization, where that program is then schematized; and skill differentiation, where that program is finally modularized. Within each of the subphases, processing levels are defined to enable the practitioner to give directions and design learning environments which will focus upon the students' gaining progressive control of the program of synergies selected for acquisition. Comments made throughout this presentation are intended to bridge the gap between motor control research and the teaching of skills, as well as encourage researchers in the motor learning/motor development areas to consider the notion of programs of muscle synergies as the fundamental explanatory unit for motor skill acquisition.     

In Vitro Fertilization: A Pastoral Taboo?

Journal of Religion and Health - Scholars have shown how the moral limitations and caveats that many religions pose against new assisted reproductive technologies have hindered women’s...     

Correction to: Autism,autistic traits and creativity: a systematic review and meta-analysis

Cognitive Processing - In the original publication of the article, the first and last names of the authors are interchanged and published incorrectly. The correct author names are given below:...     

Representations and narratives during pregnancy

In this paper, we explore how maternal representations, and in particular their contents, are structured during pregnancy. Twenty-three primiparous women were recruited for participation in a longitudinal study about mothers' thoughts and feelings about their infants. A semistructured interview was conducted with each of the subjects in the third trimester of pregnancy. During the interview, subjects were also given five adjective lists based on the semantic differential model. Results from this sample indicate similarities in the content-free aspects of representations of self and baby, but differences in the content of these presentations. Implications of these results are discussed with regard to the construction of an internal representation of the child in the third trimester of pregnancy.