On the Role of Contrast Polarity: In Response to van der Helm’s Comments

In this work, we discussed and counter-commented van der Helm’s comments on our previous paper (Pinna and Conti, Brain Sci., 2019, 9, 149), where we demonstrated unique and relevant visual properties imparted by contrast polarity in eliciting amodal completion. The main question we addressed was: “What is the role of shape formation and perceptual organization in inducing amodal completion?” To answer this question, novel stimuli were studied through Gestalt experimental phenomenology. The results demonstrated the domination of the contrast polarity against good continuation, T-junctions, and regularity. Moreover, the limiting conditions explored revealed a new kind of junction next to the T- and Y-junctions, respectively responsible for amodal completion and tessellation. We called them I-junctions. The results were theoretically discussed in relation to the previous approaches and in the light of the phenomenal salience imparted by contrast polarity. In counter-commenting van der Helm’s comments we went into detail of his critiques and rejected all of them point-by-point. We proceeded by summarizing hypotheses and discussion of the previous work, then commenting on each critique through old and new phenomena and clarifying the meaning of our previous conclusions.

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The Limiting Case of Amodal Completion: The Phenomenal Salience and the Role of Contrast Polarity

Brain Sciences ◽

10.3390/brainsci9060149 ◽

2019 ◽

Vol 9 (6) ◽

pp. 149 ◽

Cited By ~ 3

Author(s):

Pinna ◽

Conti

Keyword(s):

Perceptual Organization ◽

Amodal Completion ◽

Main Question ◽

Good Continuation ◽

Contrast Polarity ◽

Visual Phenomenon ◽

Continuous Object ◽

Limiting Case ◽

Visual Properties

In this work, we demonstrated unique and relevant visual properties imparted by contrast polarity in perceptual organization and in eliciting amodal completion, which is the vivid completion of a single continuous object of the visible parts of an occluded shape despite portions of its boundary contours not actually being seen. T-junction, good continuation, and closure are considered the main principles involved according to relevant explanations of amodal completion based on the simplicity–Prägnanz principle, Helmholtz’s likelihood, and Bayesian inference. The main interest of these approaches is to explain how the occluded object is completed, what is the amodal shape, and how contours of partially visible fragments are relatable behind an occluder. Different from these perspectives, amodal completion was considered here as a visual phenomenon and not as a process, i.e., the final outcome of perceptual processes and grouping principles. Therefore, the main question we addressed through our stimuli was “What is the role of shape formation and perceptual organization in inducing amodal completion?” To answer this question, novel stimuli, similar to limiting cases and instantiae crucis, were studied through Gestalt experimental phenomenology. The results demonstrated the domination of the contrast polarity against good continuation, T-junctions, and regularity. Moreover, the limiting conditions explored revealed a new kind of junction next to the T- and Y-junctions, respectively responsible for amodal completion and tessellation. We called them I-junctions. The results were theoretically discussed in relation to the previous approaches and in the light of the phenomenal salience imparted by contrast polarity.

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The Role of Amodal Completion in Shape Formation: Some New Shape Phenomena

Perception ◽

10.1068/p7331 ◽

2012 ◽

Vol 41 (11) ◽

pp. 1336-1354 ◽

Cited By ~ 4

Author(s):

Baingio Pinna

Keyword(s):

Stimulus Pattern ◽

Past Experience ◽

Amodal Completion ◽

Main Role ◽

Gestalt Principles ◽

Shape Formation ◽

Partially Occluded ◽

New Phenomena ◽

Shape Deformations

Amodal completion occurs when a portion of an object is hidden as a result of its occlusion behind another object. Under these conditions, the object perceived as occluded is seen as a unitary shape, whose boundary contours amodally complete behind the overlapping modal object. Kanizsa (1972, Studia Psychologica 14 208–210) and his collaborators demonstrated some effects related to the amodal completion: shrinkage of the whole figure partially occluded; expansion of the modally visible portions of the same figure; shape deformations against the Gestalt principles of regularity, simplicity, symmetry, and past experience; global increasing of colour quantity of the partially occluded figure. The aim of this work is to demonstrate that the amodal completion is not a necessary factor in inducing the previous effects. This was accomplished through phenomenological experiments whose stimuli were crucial instances (counterexamples) disproving the amodal completion hypothesis and proving the role played by the directional symmetry of the element components of each stimulus pattern. Some new phenomena demonstrated the main role of the directional shape organisation, considered as a principle of shape formation.

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Amodal Completion Revisited

i-Perception ◽

10.1177/2041669520937323 ◽

2020 ◽

Vol 11 (4) ◽

pp. 204166952093732

Author(s):

Walter Gerbino

Keyword(s):

Perceptual Organization ◽

Minimum Principle ◽

Amodal Completion ◽

Specific Reference ◽

Standard View ◽

Integrative Process ◽

Conceptual Difficulties

Amodal completion (AC) is analyzed, by looking at its historical roots and persisting conceptual difficulties. Looking at the origin of the concept, it becomes clear that it is not equivalent to perception of occluded parts. The role of fragment incompleteness is discussed, to clarify that it cannot be taken as a necessary factor for eliciting AC. The standard view of AC, depicted as a set of processes that extrapolate from veridically represented image fragments, is evaluated and rejected on the basis of evidence that AC modifies also modal parts. The theoretical importance of AC phenomena and their potential to reveal the inner forces of perceptual organization are emphasized, with specific reference to the minimum principle. Instances in which AC might be expected but does not occur are examined, to define the limits of such an integrative process.

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On the role of contrast polarity in perceptual organization: A Gestalt approach.

Psychology of Consciousness Theory Research and Practice ◽

10.1037/cns0000300 ◽

2021 ◽

Vol 8 (4) ◽

pp. 367-396

Author(s):

Baingio Pinna ◽

Livio Conti ◽

Daniele Porcheddu

Keyword(s):

Perceptual Organization ◽

Contrast Polarity

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Dubious Claims about Simplicity and Likelihood: Comment on Pinna and Conti (2019)

Brain Sciences ◽

10.3390/brainsci10010050 ◽

2020 ◽

Vol 10 (1) ◽

pp. 50 ◽

Cited By ~ 2

Author(s):

Peter A. van der Helm

Keyword(s):

Visual Perception ◽

Amodal Completion ◽

Human Visual Perception ◽

Contrast Polarity

Pinna and Conti (Brain Sci., 2019, 9, 149, doi:10.3390/brainsci9060149) presented phenomena concerning the salience and role of contrast polarity in human visual perception, particularly in amodal completion. These phenomena are indeed illustrative thereof, but here, the focus is on their claims (1) that neither simplicity nor likelihood approaches can account for these phenomena; and (2) that simplicity and likelihood are equivalent. I argue that their first claim is based on incorrect assumptions, whereas their second claim is simply untrue.

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Features of the Selectivity for Contrast Polarity in Contour Integration Revealed by a Novel Tilt Illusion

Perception ◽

10.1068/p6897 ◽

2011 ◽

Vol 40 (11) ◽

pp. 1357-1375 ◽

Cited By ~ 4

Author(s):

Stefano Guidi ◽

Oronzo Parlangeli ◽

Sandro Bettella ◽

Sergio Roncato

Keyword(s):

Luminance Contrast ◽

Opposite Polarity ◽

Contour Integration ◽

Good Continuation ◽

Distance Threshold ◽

Binding Effect ◽

Tilt Illusion ◽

Contrast Polarity ◽

The One

We studied a novel illusion of tilt inside checkerboards due to the role of contrast polarity in contour integration. The preference for binding of oriented contours having same contrast polarity, over binding of opposite polarity ones (CP rule), has been used to explain several visual illusions. In three experiments we investigated how the binding effect is influenced by luminance contrast value, relatability of contour elements, and distance among them. Experiment 1 showed that the effect was indeed present only when the CP rule was satisfied, and found it to be stronger when the luminance contrast values of the elements are more similar. In experiment 2 the illusion was reported only with relatable edges, and its strength was modulated by the degree of relatability. The CP-rule effectiveness, thus, seems to depend on good continuation. The intensity of contrast polarity signals propagating from an oriented contour might be the less intense, the more its direction deviates from linearity. In experiment 3 we estimated the distance threshold and found it to be smaller than the one found for other illusions, arising with collinear fragments. This seems to show that the reach of the contrast polarity signal inside the association field of a contour unit is shorter along non-collinear orientations than along collinear ones.

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GCC Media Roles during the 2011 Arab Spring: An Analytical and Critical Overview

Journal of Arts and Social Sciences [JASS] ◽

10.24200/jass.vol7iss2pp53-68 ◽

2016 ◽

Vol 7 (2) ◽

pp. 53 ◽

Cited By ~ 1

Author(s):

Abdullah K. Al-Kindi

Keyword(s):

Arab Spring ◽

Main Question ◽

Gulf Region ◽

The Public ◽

Gcc Countries ◽

The Media ◽

Contextual Characteristics ◽

The Arab Spring ◽

Critical Overview

The central aim of this paper is to critically analyze the role of the media during public protests that occurred in the GCC countries during 2011. These protests were part of what came to be called the “Arab Spring”, which started in late 2010. Particular focus will be on how the Arab Spring resulted in fundamental changes and how various institutions played roles in this. The study draws on Gulf region literature about the Arab Spring in order to offer a critical and informed overview on the topic under discussion. The paper’s main question is: what are the main roles played by the GCC media (old/new) during the public protests of 2011? The paper argues that the role of the media in the 2011 protests, while important, was rather limited and affected by the unique contextual characteristics of the media environment in the GCC countries.

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Knowledge in (Trans)Training and the Role of Experts: Curricula, Mathematics Education and Teacher Training, 1920-2020

Acta Scientiae ◽

10.17648/acta.scientiae.6004 ◽

2020 ◽

Vol 22 (5) ◽

pp. 65-83

Author(s):

Wagner Rodrigues Valente ◽

André Francisco de Almeida ◽

Marylúcia Cavalcante Silva

Keyword(s):

Elementary Schools ◽

Teacher Training ◽

Main Question ◽

Study Results ◽

New Knowledge ◽

In Trans ◽

Teaching Programs ◽

Changes Over Time ◽

Over Time

Background: Mathematics for basic and elementary schools and teacher education changes over time; and their official expression is given by these documents that guide teaching work in schools. Objective: What processes and dynamics are involved in the systematisation of new knowledge in the production of curriculum references? In particular, the text focuses on mathematics for the first school years. Design: The analysis of curricular reforms, considering official documents, prioritises the role of specialists, treated as experts, considering that following the actions of these researchers it may be possible to answer the main question of the study. Results: Analysis shows that the changes that have occurred over time, from teaching programs to the current BNCC, are linked to the progressive stratification of experts who go from being a highly visible public authority to an increasing set of representatives from different social segments interested in the curricular debate. Conclusions: This stratification makes it more difficult to locate those specialists responsible for the internal organisation of the proposals with regard to teaching objects, the content of mathematics to be present in teaching and teacher training.

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