Scintillating Grid Illusion Without the Grid

The scintillating grid illusion is a phenomenon where illusory black spots are perceived on white patches located at the intersections of a grid pattern. In this study, I report that the illusory spots as observed in the illusion are perceived with a stimulus pattern without grid bars. In two experiments, I investigated the perceptual properties of the scintillating illusion without grid bars. I found that the strength of the illusion depends on the contour shape of the patch components as in the scintillating grid illusion, while neither the density nor spatial alignment largely affect the illusory percepts. These findings undermine the previous theories on the mechanism of the scintillating grid illusion, as it was assumed that the grid bars are the essential component to induce the illusion. The results suggest that the illusory spots of the scintillating grid illusion could be induced by the limited processing of the patch stimuli in the peripheral vision and that the grid could play a supplementary role by enhancing the effect by further interfering with the processing.

Exploring Patterns of Sustainability Stimuli of Project Managers

Sustainable project management is becoming important and the sustainability concepts of people, the planet and profit needs to be incorporated into any type of project. This article focuses on the behavior of the project manager per se and the stimuli patterns that motivate them to adhere to sustainable project management. Three stimuli patterns are used i.e., intrinsically motivated, pragmatic and task driven. To determine which of these patterns influence a project manager, a quantitative pair-wise comparison was used. Twelve statements were used in a pair-wise comparison resulting in a combination of 66 questions. A sample of 101 project managers was analyzed to determine the stimuli patterns. The results indicate that the most prevalent stimulus pattern is the intrinsically motivated pattern with the other two patterns equally important. The results are consistent across gender, age and types of projects as well as industries. It can be concluded that for this study, project managers incorporate sustainability because they feel that it is something they should do. The motivation to consider sustainability is dominated by their behavioral beliefs and the characteristics of the project, or the opinion of others, do not play a large role. This research contributes to the larger body of knowledge with regards to sustainable project management and specifically to the human behavior of project managers. This research addresses the gap that currently exists in current literature where the focus is on the product’s sustainability and sustainable processes.

The Rotating Tilted Lines Illusion

This chapter describes the Rotating-Tilted-Lines illusion , which is a new motion illusion that arises in a circular pattern composed by black, radial lines tilted to the right and presented on a white background. When one approaches the stimulus pattern, the radial lines appear to rotate in the counterclockwise direction, whereas when one recedes from it, they appear to rotate clockwise. It is the simplest pattern able to elicit illusory rotatory motion in presence of physical radial expansion. This surprising misperception of motion seems to be a result of the competition between two motion processing units in the primary visual cortex (V1, V5)

“Invariants” in Koffka’s Theory of Constancies in Vision: Highlighting Their Logical Structure and Lasting Value

SummaryBy introducing the concept of “invariants”, Koffka (1935) endowed perceptual psychology with a flexible theoretical tool, which is suitable for representing vision situations in which a definite part of the stimulus pattern is relevant but not sufficient to determine a corresponding part of the perceived scene. He characterised his “invariance principle” as a principle conclusively breaking free from the “old constancy hypothesis”, which rigidly surmised point-to-point relations between stimulus and perceptual properties. In this paper, we explain the basic terms and assumptions implicit in Koffka’s concept, by representing them in a set-theoretic framework. Then, we highlight various aspects and implications of the concept in terms of answers to six separate questions: forms of invariants, heuristic paths to them, what is invariant in an invariant, roots of conditional indeterminacy, variability vs. indeterminacy, and overcoming of the indeterminacy. Lastly, we illustrate the lasting value and theoretical power of the concept, by showing that Koffka’s insights relating to it do occur in modern perceptual psychology and by highlighting its role in a model of perceptual transparency.