**Author details**

mentioned but we still lack a real understanding of the pathophysiology of pelvic floor disorders. Although it seems apparent that multiple factors combine in each woman for the development of a clinical condition like prolapse or UI, these need to be identified prior to treatment to avoid recurrence of disease. The genetic predisposition aggravated by acquired risk factors, such as childbirth, hormonal changes, and aging predisposes the women to PFD. There is a lack of strong evidence for this hypothesis. Findings of epidemiologic studies are frequently inconsistent. A clearer comprehension of the pathophysiology responsible for PFD is clinically relevant on different levels. First, identifying the patient population at risk through screening of known polymorphism can lead to preventive strategies and the avoidance of contributing risk factors. Second, it may allow the development of interventional therapies where we can locally modify the extracellular matrix (ECM) composition of pelvic floor muscles and ligaments. Future research should then focus on understanding what processes control ECM remodeling and aging using specific and standardized measurement methods

The pelvic floor disorders present with varied symptoms which are related to UI, FI, and POP. Although the women may present with clinical symptom of POP but they usually have backache, vaginal discharge in association with both urinary frequency and urgency and urinary leak while straining or during sexual intercourse. The fecal symptoms may occur after iatrogenic injury to anal sphincters during child birth. The prevalence of pelvic floor dysfunction is 24%, with 16% of women experiencing urinary incontinence, 9% experiencing fecal incontinence, and 3% experiencing pelvic organ prolapse [6]. The clinical presentation of pelvic floor disorders in an urogynecology clinic often lead to a diagnosis where a multidisciplinary approach is usually required for management of a case, which may include evaluation by an urogynecology radiologist. Complete diagnosis by clinical examination alone can be challenging, particularly in cases of posterior vaginal wall prolapse and/or a multicompartment problem. Imaging has become an important complementary tool in the assessment of pelvic floor disorders, and dynamic pelvic floor magnetic resonance imaging (MRI), or MR

MRI can simultaneously noninvasively evaluate all pelvic floor compartments and provide information about muscles and ligaments with great contrast resolution, without the use of

Since pelvic floor disorders present with site-specific defects, clinical presentation varies with grades of disease. The management really depends on the impact of disease on women's quality of life. The first line of management is always conservative which includes pelvic floor muscle physiotherapy, avoidance of risk factors like constipation and smoking but usually women do

defecography, has evolved as one of the essential imaging techniques [7].

ionizing radiation and with minimal patient discomfort [8].

**4. Treatment**

2 Pelvic Floor Disorders

and tracing them back to genetic transcription [5].

**3. Clinical symptoms and diagnosis**

Raheela M. Rizvi

Address all correspondence to<EMAIL_ADDRESS>
Obstetrics and Gynecology, Agha Khan University, Karachi, Pakistan

## **References**

**Chapter 2**

**Provisional chapter**

**Pathophysiology of Pelvic Organ Prolapse**

**Pathophysiology of Pelvic Organ Prolapse**

DOI: 10.5772/intechopen.76629

Pelvic organ support is provided by interaction between the pelvic floor muscle, ligaments and its connective tissues. Failure of anatomical support may result in pelvic organ prolapse. Therefore in managing anterior, posterior, or apical compartments prolapse, conceptual understanding of pelvic floor anatomy is essential for the surgeons. To appropriately treat these entities, comprehension of the various theories of the pathophysiology of pelvic organ prolapse is of paramount importance. DeLancey has described vaginal connective tissue support of the pelvis at three levels that has helped us to understand various clinical manifestations of pelvic organ support dysfunction. Pelvic floor disorder is frequently associated with etiological risk factors which include aging, parity, obesity, connective tissue disorder, increased intra-abdominal pressure and hysterectomy. A better understanding of pathophysiology of muscular, collagen, and neuronal components of the pelvic organs and

their support would provide an insight of site specific defects and its prevention.

**Keywords:** prolapse, anatomy, pelvic floor muscles, compartments, collagen, risk

Approximately one-third of adult women affected with pelvic organ prolapse, have significant impact on their quality of life and emotional well-being. Epidemiologic survey of the United States showed that pelvic organs prolapse (POP) becomes more prevalent as the population age advances [1]. Women have 11.1% lifetime risk of undergoing surgery for prolapse

Pelvic organ prolapse is defined as the descent of the anterior, posterior, and/or apical vaginal compartment(s) with protrusion of one or more pelvic organs (e.g. bladder, uterus,

by age 80 [2] and a 30% risk of reoperation over a period of 4 years [3].

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.76629

Lubna Razzak

Lubna Razzak

**Abstract**

factors

**1. Introduction**

#### **Pathophysiology of Pelvic Organ Prolapse Pathophysiology of Pelvic Organ Prolapse**

DOI: 10.5772/intechopen.76629

#### Lubna Razzak Lubna Razzak

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.76629

**Abstract**

Pelvic organ support is provided by interaction between the pelvic floor muscle, ligaments and its connective tissues. Failure of anatomical support may result in pelvic organ prolapse. Therefore in managing anterior, posterior, or apical compartments prolapse, conceptual understanding of pelvic floor anatomy is essential for the surgeons. To appropriately treat these entities, comprehension of the various theories of the pathophysiology of pelvic organ prolapse is of paramount importance. DeLancey has described vaginal connective tissue support of the pelvis at three levels that has helped us to understand various clinical manifestations of pelvic organ support dysfunction. Pelvic floor disorder is frequently associated with etiological risk factors which include aging, parity, obesity, connective tissue disorder, increased intra-abdominal pressure and hysterectomy. A better understanding of pathophysiology of muscular, collagen, and neuronal components of the pelvic organs and their support would provide an insight of site specific defects and its prevention.

**Keywords:** prolapse, anatomy, pelvic floor muscles, compartments, collagen, risk factors


**2. Grid computing with globus**

268 Grid Computing – Technology and Applications, Widespread Coverage and New Horizons

Properties Valanis [4] CHEN [5] MIR [6] MOUGIAKAKOU [7] Contrast Entropy Correlation Homogeneity

Energy

MRI. The measurements identified in various approaches are indicated by a tick. The SGLCM approach undertaken by Valanis et al. [4] was to classify three hepatic tissues: normal, hemangeoma and hepatocellular carcinoma on CT images with a resolution of 512 X 512 pixels and 8 bits per pixel (bpp) (256 grey levels). Correlation, inverse difference moment and cluster tendency were shown in the paper to achieve classification rates of up to 90.63% after being applied with feature selection based on a Genetic Algorithm (GA) approach. Of particular interest is an approach by Chen [5], using a modified probabilistic neural network (MPNN) to classify liver tumor, hepatoma and hemangeoma on CT images with 12 bpp representing 4096 grey levels and resolution of 320 X 320 pixels. The entropy and correlation showed better performance than other features extracted from co-occurrence matrices at directions θ = 0°, 45°, 90° and 135°, resulting in a classification rate of 83% where the misclassification resulted from the tumor matrices block size. The classification rate could be increased by reducing the block size. Another approach was by Mir [6] to classify normal and malignant liver on 256 X 256 pixels CT images. Entropy and local homogeneity were found to be consistent within a class and most appropriate for discrimination of the malignant and normal liver. Mougiakakou [7] implemented an automated CAD system for characterization of liver CT images into cysts, hepatoma and hemangeoma using a multiple NN classification scheme. Contrast, entropy, correlation and homogeneity were the identified features based on feature selection using the Squared Mahalanobis Distance as the

MRI produces images of the insides of the body. Unlike an X-ray, MRI does not use radiation. Instead, a magnetic field is used to make the body's cells vibrate [1]. The vibrations give off electrical signals which are interpreted and turned into very detailed images of "slices" of the body. MRI may be used to make images of every part of the body, including the bones, joints, blood vessels, nerves, muscles and organs. Different types of tissue show up in different grayscale intensities on a computer-generated image. In this study, series of MRI images were acquired from the Diagnostic Imaging Department of Selayang Hospital, Malaysia, using a Siemens Magnetom Avanto, 1.5T MRI Scanner. The sample liver MRI images (256 X 256 pixels, 12 bps) were acquired consisting of sets of cyst,

Inverse Difference Moment

Table 1. SGLCM properties for second-order statistical measurements. The features

Cluster Tendency

fitness function [8].

**1.1 Image acquisition**

liver tumor and healthy liver, for training and testing.

Angular Second Moment

successfully examined in prior work are summarized in Table 1 below.

Grid Computing describes computation in which jobs are run on a distributed computational unit spanning two or more administrative domains. It has sparked tremendous excitement among scientists worldwide and has renewed the interest of the scientific community toward distributed computing, an area which was almost forgotten during the 90's.

The Globus toolkit [4] was created in the late 1990s as part of a joint research project between Argonne National Laboratory and the Information Sciences Institute at the University of Southern California. Its aim was to provide a solution to the computational needs of large virtual organizations [4] that span multiple institutional and administrative domains. Globus is a middleware toolkit that provides fundamental distributed computing services such as authentication, job starting and resource discovery.

Globus provides a collection of services [5] including: GSI, Grid Security Infrastructure which provides authentication based on a Certificate Authority trust model; GRAM, Grid Resource Allocation Manager which handles job starting or submission; GridFTP, providing extensions to the FTP standard to provide GSI authentication and high performance transfer; MDS, Monitoring and Discovery Service enabling remote resource discovery.

By itself Globus does not provide all of the tools and services required to implement a full featured distributed computing environment. Additional tools are available to fill some of the gaps. The National Center for Supercomputing Applications (NCSA) provides a patch to add GSI authentication to OpenSSH. This allows Globus environments to have terminal based single-signon. Globus does not provide any scheduling functionality, but rather relies on the client operating system scheduler or batch schedulers such as OpenPBS [6] to handle local scheduling activities.

Global scheduling between Globus processes can be provided by meta-schedulers, such as Condor-G [6]. Condor-G submits jobs to the GRAM service running on Globus nodes and GRAM handles the task of submitting the job to the local scheduling system.


**Preface to "Ubiquitous Technologies for Emotion Recognition"**

Emotions play a very important role in how we think and behave. As such, the emotions we feel every day can compel us to act and influence the decisions and plans we make about our lives. Being able to measure, analyze, and better comprehend how or why our emotions may change is thus of much relevance to understand human behavior and its consequences. Despite the great efforts made in the past in the study of human emotions, it is only now, with the advent of wearable, mobile, and ubiquitous technologies, that we can aim to sense and recognize emotions, continuously and in real time. This book brings together the latest experiences, findings, and developments regarding ubiquitous sensing, modeling, and the recognition of human emotions.

> **Oresti Banos, Luis A. Castro, Claudia Villalonga** *Editors*

### *Editorial* **Ubiquitous Technologies for Emotion Recognition**

**Oresti Banos 1,\* ,†,‡ , Luis A. Castro 2,‡ and Claudia Villalonga 1,‡**

**Abstract:** Emotions play a very important role in how we think and behave. As such, the emotions we feel every day can compel us to act and influence the decisions and plans we make about our lives. Being able to measure, analyze, and better comprehend how or why our emotions may change is thus of much relevance to understand human behavior and its consequences. Despite the great efforts made in the past in the study of human emotions, it is only now with the advent of wearable, mobile, and ubiquitous technologies that we can aim at sensing and recognizing emotions, continuously and in the wild. This Special Issue aims at bringing together the latest experiences, findings, and developments regarding ubiquitous sensing, modeling, and recognition of human emotions.

**Keywords:** affective computing; emotion recognition; artificial intelligence; machine learning; image processing; video processing

There is an increased interest in studying facial expressions and how they relate to emotions. Lately, some research has been carried out to enhance in-vehicle interactions for drivers. This increased interest has been mainly focused at increasing road safety such as driver drowsiness, distracted driving, or detecting drivers' stress. In [1], they proposed a novel contactless method for detecting stress in drivers. This method is based on the extraction of features from thermal infrared imaging, which were obtained in a controlled environment with 10 subjects. In their work, they compared their results with a stress index obtained from electrocardiography (ECG). They used a binary classifier to discriminate among drivers with stress vs. those with no stress, resulting in classification performance with an AUC of 0.80, a sensitivity of 77%, and a specificity of 78%. The results are promising towards identifying driver states that can derive in situations that can be of interest for road safety. In addition to this work, the authors of [2] implemented a system to monitor the driver's facial expressions to assess health risks such as severe pain episodes while driving. The proposed approach is based on line-segment feature analysis-convolutional recurrent neural network (LFA-CRNN), which had the highest accuracy at approximately 98.92%. The results of this work aim at alerting the driver to risk-related matters while driving.

Furthermore, using facial expressions, Ref. [3] present a novel system for automatically detecting pain in babies using image analysis. They implemented a classifier based on Support Vector Machines (SVM) using the following texture descriptors for pain detection: Local Binary Patterns, Local Ternary Patterns, and Radon Barcodes. Using the Infant COPE database, the authors obtained accuracy around 95%. The approaches of [2,3] both use facial expressions to detect pain, although they use different databases and features. Still, these works provide valuable results that can be applied in systems for increasing and monitoring safety and health.

Image-based emotion recognition is mostly based on the analysis of whole-face images. However, some approaches put the focus on core facial areas (eyes, nose, mouth, etc.), which normally encode most of the affective information. In [4], the authors multi-block

**Citation:** Banos, O.; Castro, L.A.; Villalonga, C. Ubiquitous Technologies for Emotion Recognition. *Appl. Sci.* **2021**, *1*, 0. https://doi.org/

Received: 21 July 2021 Accepted: 27 July 2021 Published: 29 July 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

deep learning techniques which are trained on core facial areas. They show its application in an app for interview self-management. The same principle is used in [5]. Here, the authors propose the use of convolutional neural networks for the automatic recognition of micro-expressions in real-time. Although the accuracy results are far from optimal, they appear quite promising, especially concerning the time taken to recognize the emotion (a few milliseconds).

Regular RGB cameras are most frequently used in facial expression-based emotion recognition. However, there is a growing bulk of research devoted to using thermal infrared cameras to this very end. In [6], the authors review the application of thermal infrared imaging to determine affective responses ascribed to physiological modulations. Their review outlines the main advantages and challenges of thermal imaging-based affective computing, with a particular focus on its use for human–robot interaction applications.

The automatic recognition of emotions has been largely based, according to the literature, on image or video data. Nonetheless, other types of data are used to identify people's affective states. For example, Ref. [7] analyzes the audio data generated during phone calls in a call center. The authors use speech emotion recognition to determine the call urgency, giving greater priority to calls featuring emotions such as fear, anger and sadness, and less priority to calls featuring neutral speech and happiness. The results show a significant reduction in waiting time for calls estimated as more urgent, especially those calls presenting emotions of fear and anger.

Electroencephalogram (EEG) signals are another alternate data used for emotion recognition. EEG-based emotion recognition is particularly considered due to its effectiveness compared to body expressions and other physiological signals. In [8], the authors study the use of various statistical techniques, namely logistic regression, Gaussian kernels and Laplacian priors to automatically recognize a set of emotions. They also investigate the critical frequency bands in emotion recognition, concluding a superiority of gamma and beta bands while classifying emotions. The great volume of data generated by EEG approaches makes it particularly interesting to consider using deep learning techniques. In [9], the authors precisely use such techniques with the aim to help determining the attitude of consumers towards a product. The authors prototype their solution with a well-known emotion recognition dataset and they show accuracy results comparable to those obtained via traditional machine learning approaches.

**Author Contributions:** All authors contributed equally to the screening, review, and assessment of the submitted papers. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** Thanks to all the authors who submitted their research for this Special Issue. The invaluable contribution of the international reviewers is gratefully acknowledged.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

*Article*


**1. Introduction**

Van der Helm [1] commented in a surprisingly polemical way on a recent paper of ours [2]. In this work, we answer his comments by proceeding in an objective manner on the basis of what was truly written and demonstrated in that paper on the basis of mere phenomenal evidence. In addition to the previous conditions, several others will be shown to make even more clear to the reader our previous purposes and conclusions, as well as the following counter-comments.

Our reply will be organized into sections based on van der Helm's comments. However, primarily for the sake of clarity, a short summary of Pinna and Conti [2] is required. This is useful to correctly inform readers about our previous purposes and conclusions necessary for a better understanding of our responses.

### **2. Pinna and Conti (2019) in Short**

In this work, we demonstrated unique and relevant visual properties imparted by contrast polarity in perceptual organization and, more particularly, in eliciting amodal completion, where T-junction, good continuation, and closure are considered as the main factors involved.

Some of the most relevant explanations of amodal completion based on Helmholtz's likelihood principle [3] and Gregory's "unconscious inference" [4] were discussed. In short, the amodal object is similar to a perceptual hypothesis postulated to explain the unlikely gaps within the pattern of stimuli and the one that most likely produces the sensory stimulation (cf. the so-called avoidance-of-coincidences principle [5,6]). More recently these approaches have been reconsidered in terms of probabilistic Bayesian inference, applied successfully in many classical amodal conditions.

Another approach discussed within the paper is the simplicity–Prägnanz principle of Gestalt psychologists, according to which the visual system is aimed at finding the simplest and most stable organization consistent with the sensory inputs.

These approaches focus on the shape completed behind the occluder by assuming amodal completion as the cause of the formation of the shape partially occluded. Therefore, the main interest is to account for how the occluded object is completed, what is the amodal shape, and how contours of partially visible fragments are relatable behind an occluder.

Di fferently, we adopted a complementary perspective, assuming amodal completion not as the cause but as the resulting e ffect. Therefore, the questions are now the following: What is the role of shape formation and perceptual organization in inducing amodal completion? What are the perceptual conditions that elicit the segregation of occluded and occluding objects and, finally, amodal completion? What is the role of the local contours, junctions, and termination attributes in eliciting the phenomenon of amodal completion?

Within this perspective, amodal completion was considered as a visual phenomenon not as a process, i.e., the final outcome of perceptual processes and grouping principles. Therefore, the contrast polarity has been used as the main grouping and ungrouping factor aimed to explore and test amodal completion as a visual phenomenon elicited by good continuation, T-junctions, closure, and regularity.

Together with traditional configurations, novel stimuli, which have been reduced more and more to extreme limiting conditions, were introduced.

Phenomenally, we showed that contrast polarity is e ffective in inducing amodal completion in conditions where, on the basis of the known principles and of the previous theoretical approaches, it is not expected and vice versa. In this way, amodal completion was annulled or disrupted in the stimuli where it was supposed to be e ffective. More particularly, contrast polarity has been able to elicit/disrupt amodal completion when pitted against or in favor of the following conditions reduced to limiting cases: (i) Classical patterns (Figures 7 and 8); (ii) Petter's e ffect and Petter's rule (Figures 9–11); (iii) tessellation with T-junctions replaced by Y-junctions (Figures 12–16); (iv) group of isolated figures arranged in a cross (Figures 17–19); and (v) a single shape (Figures 20–22).

Our results demonstrated the compelling domination of the contrast polarity against good continuation, T-junctions, closure, 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. They were called I-junctions, since eliciting amodal continuation of contours behind a contour with the same orientation.

Under our conditions, contrast polarity was shown to operate locally, eliciting results that could be independent from global scale and also paradoxical. We suggested that these results weaken and challenge theoretical approaches based on notions like oneness, unitariness, symmetry, regularity, simplicity, likelihood, constraints, and past knowledge. Moreover, Helmholtz's likelihood principle, simplicity/Prägnanz, and Bayes' inference are clearly questioned since they are supposed to operate especially at a global and holistic level of vision.

We proposed an alternative explanation of the specific outcomes based on the phenomenal dynamics made explicit by contrast polarity. First of all, the contrast polarity was perceived like a barrier analogous to, but stronger than, the one created by T-junctions. In other terms, the phenomenal salience, elicited by the highest luminance contrast going from black to white on a gray background, triggers a process of object segregation and unilateral belongingness of the boundaries.

The dominance of contrast polarity over good continuation, closure, regularity, and T-junctions is related to its phenomenal salience and highlighting e ffect. The same argument can account for the emergence of amodal continuation on I-junction, groups of isolated figures, and single shapes. Moreover, the imparted salience can disrupt, both locally and globally, arrangements of figures or can alternately rearrange the elements according to their similarity/dissimilarity. The highlighting strength of contrast polarity determines even the grouping e ffectiveness against the global and holistic rules and factors.

In favor of the basic and essential role of the phenomenal salience, we invoked deceiving strategies used in nature by most living organisms. Flowers, birds, and fishes use colors and contrast polarity to attract, reject, show, and hide. We suggest that the phenomenal salience strongly improves the biological fitness of living organisms and, therefore, the capability of an individual of a certain genotype to reproduce and, thus, to propagate an individual's genes within the genes of the next generation.

The phenomenal salience is a basic requirement also in human beings, in the way we dress, invent fashion and design, in the way we use the maquillage, and in the existence of the maquillage itself.

The strength of phenomenal salience imparted by contrast polarity enables the full independence from local or global organizations and top-down or bottom-up dynamics. It eludes all these categories since it can play in favor or against each of them, as demonstrated in our stimuli. It represents a true challenge for the theories discussed here, which cannot easily incorporate it (e.g., as a prior) without losing explanatory power somewhere else. Inside these arguments, it is important to underline that phenomenal salience is a perceptual attribute not restricted to contrast polarity, but it can also be triggered by color, shape, motion, and every other visual property. Among them, contrast polarity is one of the most powerful.

Given the significance of this attribute, further experimental studies based on phenomenological, psychophysical, and neurophysiological techniques are required to measure the strength of the phenomenal salience imparted by contrast polarity against other attributes involved in amodal completion. Further studies can shed light on the role of contrast polarity as a general tool useful in testing the range of scientific e ffectiveness of visual theories, approaches, and models.

This summary is taken on purpose almost verbatim from the final Discussion section of Pinna and Conti.

To make clear these hypotheses and, above all, to demonstrate the partial and incorrect interpretations and judgments of van del Helm, it is necessary to show the way we operate with reversed contrast. This is a novel way that cannot be reduced to the examples reported by van der Helm. This is the topic of the next section.

### **3. Phenomenology of Contrast Polarity**

Van der Helm wrote: "The role of contrast polarity in human visual perception is a long-standing research topic (see, e.g., [7–10]). As a consequence, the phenomena presented by Pinna and Conti are not really as novel or surprising as they suggested them to be, but they are indeed illustrative of the effects of, in particular, contrast polarity reversals. For example, Figure 1 shows, in the style of Pinna and Conti, a stimulus in which such a reversal triggers a substantial change in the way in which it is perceptually organized."

As mentioned in the previous section, contrast polarity has been used in our paper as a grouping/ungrouping factor aimed to explore and test amodal completion as a visual phenomenon elicited by good continuation, T-junctions, closure, and regularity. It is no coincidence that the title of our work is: "The Limiting Case of Amodal Completion: The Phenomenal Salience and the Role of Contrast Polarity." A first di fference in relation to the works [3–7], mentioned by van der Helms, is in the purposes but, more importantly, in the pattern of stimuli. In fact, while it is true that the quoted papers studied the role of contrast polarity, none of them used this factor the way we did, as can be easily demonstrated through their reading and especially by comparing their conditions with ours.

This entails that, di fferently from van der Helm's words—"The role of contrast polarity in human visual perception is a long-standing research topic (see, e.g., [7–10]). As a consequence, the phenomena presented by Pinna and Conti are not really as novel or surprising as they suggested them to be ... .")—the conclusion, "As a consequence," cannot be a correct logical implication. The fact that other scientists studied "the role of contrast polarity in human visual perception" does not imply that our conditions are not new. In fact, although the first proposition is true, the second is not necessarily true and false, as we are going to demonstrate. As a consequence, the resulting implication is false according to the associated logic truth table.

This is not enough for a proper defense. We will now demonstrate the novelty of our conditions by showing some of them with further supporting examples. We will proceed going from known and trivial cases, as the one shown by van der Helm, to more and more interesting cases and demonstrations.

We start again from van der Helm's words already quoted: " ... For example, Figure 1 shows, in the style of Pinna and Conti, a stimulus in which such a reversal triggers a substantial change in the way in which it is perceptually organized."

The example reported is only partially in our style. To be more precise, it is just the starting condition that in our paper became much more complex figure after figure. Van der Helm played here with perceptual grouping by pitting similarity against good continuation. This is a classical procedure used by Gestalt psychologists. A similar basic condition is illustrated in the following stimulus (cf. Figure 1).

**Figure 1.** Crosses or stars? Alternated figure-ground segregation.

Here, we do not perceive individual segments, unconnected and oriented in di fferent directions, but we see two main alternated and complementary shapes: Crosses and eight-pointed stars. By perceiving the crosses, the stars are invisible and vice versa. This is related to the unilateral belongingness of the boundaries. The two main results of Figure 1 are reversible and they can be easily switched by changing the focus of attention or just by moving the gaze in di fferent locations of the stimulus pattern.

By introducing the grouping principle of similarity on the basis of the reversed luminance contrast, the salience of the crosses is now enhanced to the detriment of the stars (Figure 2, left). The opposite outcome is perceived in Figure 2, right.

The story becomes more interesting in Figure 3, where, reversing the contrast of only one of the two objects is su fficient to highlight and, thus, elicit the emergence of all the other similar objects. The accentuation of one object (e.g., one cross) spreads to all the others (all the remaining crosses). This figure suggests that reversed contrast could act as an accentuation principle [11–16] and not just as similarity.

The strong connection between figure-ground segregation and grouping is clearly shown in Figure 4, where the closure and proximity principles induce a clear object segmentation: Stars on the left and crosses on the right.

**Figure 2.** Crosses and stars due to the similarity principle of contrast polarity.

**Figure 3.** Crosses and stars spreading and filling in.

**Figure 4.** Crosses and stars elicited by the closure and proximity principles.

In Figure 5, contrast polarity enables the emergence of the complementary regions or, at least, it weakens the results of Figure 4.

**Figure 5.** Similarity by contrast polarity pitted against closure and proximity principles.

Figure 6 shows a further and more interesting example, already reported within the paper.

**Figure 6.** Similarity by contrast polarity pitted against closure and proximity principles.

Further conditions are illustrated in Figure 7. Here, by overlapping six stars, the grouping of the components, recombined by contrast polarity, becomes even more complex and unexpected.

Under these conditions, the regularity and homogeneity of the resulting object is impaired.

The strength of contrast polarity in terms of salience against other principles can be further perceived and appreciated in Figures 8 and 9.

Note that we are now introducing the term "salience," as a phenomenal attribute imparting a strong highlighting effect. Under these conditions, contrast polarity is used as a special case of the similarity principle, i.e., one of the many possible kinds of similarity, but in the next figures, due to the salience effect, it can be considered as a special case of the accentuation principle.

It is worth emphasizing that among the similarities, the reversed contrast is, in our opinion, one of the strongest and likely the strongest factor, and, as it happens in Figure 9, this is due to its highlighting effect that immediately jumps to the eye. Here, starting from two nested eight-pointed stars, namely, from two simple, singular, symmetrical, and Prägnant figures, we can highlight and then pop out new configurations.

**Figure 7.** New complex results by overlapping six eight-pointed stars.

**Figure 8.** New regular and simpler results elicited by contrast polarity.

**Figure 9.** Different results on the basis of contrast polarity.

Figure 10 shows Figure 9a that becomes a sort of intertwined flower-like spiral without clean and univocal external boundaries.

**Figure 10.** An intertwined flower-like spiral.

Regularity and likelihood of the previous figures become irregular and unlikely in Figure 11 and, more efficiently, in Figure 12.

**Figure 11.** Iregular shapes from contrast polarity.

**Figure 12.** Regular and irregular shapes from reversed contrast.

From these examples, contrast polarity is not used as a similarity principle but more and more to accentuate and highlight new elements previously invisible and camouflaged. This idea, already discussed in our paper, will be developed in the next figures starting from the following variations of Necker cube (cf. Figure 13).

**Figure 13.** Different views of the Necker cube (first row) and weakened, disrupted, camouflaged, and invisible cube (second row).

What is worthwhile to be considered in this figure is the set of cubes of the first row, where highlighting one view or the other, by means of reversed contrast, the same cube seems to be differently oriented in 3D space. The reversed contrast is now more related to accentuation principle than to similarity.

Given the salience effect, we finally explore limiting conditions, more directly related to simplicity and likelihood approaches. These conditions represent a further level of application of the reversed contrast, no more within multiple contours highlighting, disrupting, or camouflaging one or another possible configuration, but within a unique closed shape, more simple as possible, and where the

possibility to perceive further inset subcomponent is very unlikely. These cases allow to test more appropriately simplicity and likelihood. Some of these conditions are illustrated in Figure 14.

**Figure 14.** The black boundaries of a regular eight-pointed star discontinued by reversing the contrast polarity.

Now, the black boundaries of a regular eight-pointed star have been discontinued by reversing the contrast polarity in different portions of each figure. In terms of grouping, the closure principle is mainly responsible for the perception of the eight-pointed star. Phenomenally, the uniqueness and wholeness of each star illustrated appear weakened or broken down. Each shape of the first row partially splits into two black and white adjacent components that are seen as belonging to two different objects.

The most extensive black components reveal more easily the whole shape that, given the ungrouped white sides, do not appear as eight-pointed stars, but as the related shapes illustrated in Figure 14b, with inner gaps interrupting the boundary continuation. The removal of the white components improves the grouping of the black segments on the basis of the closure and good continuation principles. The missing sides do not affect the whole shape but appear as gaps favoring the good continuation of the modal sides and the amodal wholeness [12]. Given the black and white alternation of the sides, only the last condition of the first row appears as analogous to the star of the last condition of Figure 14b.

Further examples are illustrated in Figure 15. Again, the reverse contrast breaks the oneness and the unitariness of the eight-pointed star and influences significantly its shape. New organizations emerge as follows: A concave polygonal shape rather than a star (Figure 15a); two rotated and perpendicular intersecting square shapes with illusory curved sides (Figure 15b); irregular shapes different from stars in Figure 15c–g. Figure 15h is the control.

Figure 15a,b display something that is worth noticing, namely the emergence of the concavity and of the convexity within the same geometrical star. As a matter of fact, the two figures are perceived as stars. However, the first appears as a sort of 'eight-concave star' or 'eight-indented star.'

The breaking of the uniqueness and unitariness is very effective even though good continuation, closure, and Prägnanz together favor the grouping. The dissimilarity imparted by the reversed contrast split the figure. The question is: Why are these irregular and parceled solutions preferred to a simpler result like 'a star with black and white edges?' With this solution, both the whole shape and the local changes would have been preserved and saved. Even if this ideal solution is possible, it does not prevail.

These outcomes clearly challenge the theoretical assumptions of oneness, unitariness, symmetry, regularity, simplicity, minimization of description length, likelihood, and previous knowledge.

These limiting conditions can be even more pushed over by drastically reducing the role of the discontinuities due to the reversed polarity and, therefore, by improving the good continuation and the similarity of remaining parts of the figure. This is the case of the polygons illustrated in Figure 16, where the perception of a polygon is the only possibility with the maximum likelihood.

**Figure 15.** Further examples of the role played by contrast polarity in breaking the unitariness of a star.

**Figure 16.** Octagons apparently different due to the accentuation imparted by contrast polarity.

In Figure 16 top-center, a regular octagon is perceived with the vertices oriented along the main directions of space (vertical and horizontal). By introducing achromatic discontinuities on two vertices placed along the vertical or on the horizontal axes of the polygon (second and third figure in the first row), the same kind of oriented regular octagon is seen. However, by introducing similar discontinuities in two opposite sides placed along an oblique axes (second and third figure in the second row), the polygons are now perceived as equal and, at the same time, different: Their shapes appear more similar to the first octagon of the second row, i.e., with the sides, rather than the vertices, oriented along the main directions of space. Moreover, the second and third octagons of the second row appear as oriented on opposite oblique directions with respect to the vertical axes.

Similar results can be produced with just a single white discontinuity (see Figure 17).

**Figure 17.** The octagons appear different due to a single white accentuation imparted by the contrast polarity.

Unlike the stars of Figures 14 and 15, the wholeness of the polygons is not broken down or disrupted. This effect mainly occurs due to the significant size reduction of the white components that let the good continuation and, hence, the unitariness and the wholeness of the boundaries at work. Phenomenally, the white discontinuities, placed on the vertices (angles) and sides, highlight and accentuate within the same shape different components (angles and sides) and object attributes.

The white dashes within the polygons behave phenomenally like accents inducing the pop out of one or another geometrical basic component of the polygon, i.e., angle or side. The white dashes do not represent the source of the disruption of the object, as shown in the previous figures, but behave like accents of a specific attribute of the figure that is ipso facto highlighted. This accent determines a change of the whole object, not only of its orientation or tilt, but of one of the two attributes. In other terms, the accent changes the nature and the geometry of the object. The accentuated pointedness and sidedness create two different polygons (same but different), one more pointed and the other flatter.

The accentuation induced by contrast polarity can also disrupt the regularity of the octagons as illustrated in Figure 18.

**Figure 18.** The octagons appear irregular and oriented in opposite directions.

### *Counter Comments: Reversed Contrast and Amodal Completion*

Differently from van der Helm's judgment, the stimuli presented in this section demonstrate the novelty of the way contrast polarity was used.

It is surprising that van der Helm based his critiques only on the example produced by himself and not on our stimuli. This is unfair, and in our view, scientifically inappropriate, to quote the same words used by van der Helm. It would have been scientifically more correct to comment in detail on each of our figures.

Further interesting conditions for the discussion are shown in Figures 19–21. In Figure 19, the reversed contrast is pitted in favor or against T-junctions, good continuation, closure, simplicity, and likelihood. A detailed description of this set of stimuli can be found in our paper.

**Figure 19.** Conditions demonstrating the dominance of the contrast polarity over good continuation, T-junctions, regularity, simplicity, and likelihood.

Unfortunately, van der Helm did not discuss these stimuli that represent the core of our work. Moreover, he did not notice the novelty of the I-junctions, more clearly shown in Figure 20 (Figure 21 is a control), where the continuation of contours is behind a contour with the same orientation. In other terms, two contours, although showing the same orientation, are perceived as two different contours where one appears to complete amodally behind the other. The effect of the I-junctions occurs against T-junctions, regularity, good continuation, closure, simplicity, likelihood. For a detailed description of this novel outcome see Pinna & Conti [2].

**Figure 20.** The contrast polarity reverses the amodal completion: The square is now perceived as partially occluded by the asymmetrical objects (for a control see Figure 21).

**Figure 21.** A control for Figure 20. The figures, partially occluded by the square, complete amodally as asymmetrical shapes.

### **4. On Local vs. Global Assumption: Likelihood and Simplicity**

Van der Helm judged and labelled three sentences of our paper as incorrect assumptions. The sentences are the following:

A simple response to this judgement is that the three sentences are not assumptions but just evidence based on our results and on the phenomenology of the stimuli. On the contrary, we think that van der Helm's judgement is based on an incorrect assumption. In fact, he did not comment on the three sentences on the phenomenology of our effects, i.e., by showing and demonstrating that our results are not consistent with our conclusion. Instead, he assumed as incorrect our sentence on the base of the following results obtained by van Lier:

*It is true that simplicity and likelihood approaches may aim to arrive at global stimulus interpretations, but a general objection against the above stance is that they (can) do so by including local factors as well. For instance, van Lier [16] presented a theoretically sound and empirically adequate simplicity model for the integration of global and local aspects in amodal completion.*

We think that this is unfair and scientifically inappropriate, in his own words. In fact, he continues:

*A methodological objection is that Pinna and Conti introduced contrast polarity changes in stimuli but pitted these against alleged simplicity and likelihood predictions for the unchanged stimuli. As I specify next, this is unfair, and in my view, scientifically inappropriate.*

Starting from our purpose—according to which contrast polarity has been used as the main grouping and ungrouping factor aimed to explore and test amodal completion as a visual phenomenon

elicited by good continuation, T-junctions, closure, and regularity—this is not unfair and it is not scientifically inappropriate since our predictions are not based on unchanged stimuli but, on the contrary, on changed stimuli. For example, in the case of Figure 21 of our paper, we stated: "The breaking of the uniqueness and unitariness is very e ffective even though good continuation, closure, and, even, Prägnanz together favor the grouping. The dissimilarity imparted by the reversed contrast splits the figure. The question is: why are these irregular and parceled solutions preferred to a simpler result like 'a star with black and white edges?' With this solution, both the whole shape and the local changes would have been preserved and saved. Even if this ideal solution is possible, it does not prevail."

A further van der Helm's critique states as follows:

*Pinna and Conti wrote "[If] we do not consider the contrast polarity as a constraint or as a prior, Bayes' inference cannot easily explain these conditions" [2] (p. 12 of 32)—indeed, but why would we? Hence, they knowingly ignored the above flexibility and applied likelihood as if it is fundamentally blind to contrast polarity. Thereby, they missed the mark in their assessment of likelihood approaches.*

We did not ignore the flexibility of the Bayesian approach; in fact we wrote: "Bayes' inference cannot easily explain these conditions." We just reported the most immediate prediction that could be made and leave open the point. Nevertheless, van der Helm based his judgement on vague conjecture and this cannot be accepted. On the contrary, it would have been acceptable whether he had explained our stimuli according to Bayesian inference.

We do deny that this kind of explanation might be possible, we are not against Bayesian inference, but we just casted doubts about its e ffectiveness in the light of our stimuli.

In commenting on simplicity, van der Helm refers to Figure 2, introduced by himself, and draws conclusions on our work by stating: "Pinna and Conti knowingly ignored this and applied simplicity as if it is fundamentally blind to contrast polarity. Thereby, they missed the mark in their assessment of simplicity approaches". We cannot accept this gratuitous judgment and critique based on general hypothesis, far away from our work. We really do not understand this attitude. We would have preferred a direct comment to each of our figures. This is much more useful to improve theories, useful for science.

Anyway, we have never said that simplicity is blind to contrast polarity. We do not believe so. Our phenomenological background is based on the notion of simplicity. Our point was just focused on the conditions we studied. As a matter of fact, our results put to the test these important theories and approaches in line with Popper's falsificationism. This is scientifically appropriate.

### **5. On the Equivalence between Simplicity and Likelihood**

Van der Helm quoted the unique sentence in our paper where he thinks we claim the equivalence between simplicity and likelihood: "[...] the visual object that minimizes the description length is the same one that maximizes the likelihood. In other terms, the most likely hypothesis about the perceptual organization is also the outcome with the shortest description of the stimulus pattern." [2] (p. 3 of 32). He also wrote: "This is an extraordinary claim".

As a first reply to this comment, we can confidently say that it was far from our purpose to demonstrate or discuss the supposed equivalence. Our purposes were very di fferent as described in detail in the first section of the present work. Second, the supposed equivalence is just related and based on our conditions only without any further generalization. In our opinion, based on our results, simplicity and likelihood do not deliver di fferent predictions. For van der Helm, it would have been easier to indicate possible di fferences to give a more e ffective contribution.

We cannot accept that van der Helm can attribute to us generalizations never mentioned. Again, the supposed equivalence is implicit and restricted to only our conditions. We did nothing to prove or disprove this equivalence being far from our purposes. Third, in any case, as acknowledged even by van der Helm, this equivalence is not an extraordinary claim. Other scientists (see below) are in favor of some sort of equivalence.

According to Helmholtz's likelihood principle, the sensory input is organized into the most probable distal object or event consistent with the sensory data (the proximal stimulus). This principle chooses the most likely true interpretation and assumes that the visual system is highly veridical in terms of the external world. From an evolutionary point of view, if the visual system were not veridical, it would probably not have survived during the evolution.

On the other hand, the simplicity principle does not experience these problems, because it does not aim specifically at veridicality. The simplicity and the likelihood principle are two competing theories [5,17–19] of perceptual organization and visual coding, which are difficult to settle because neither of the key elements were clearly defined. The general difference between the two is related to the fact that the visual system, in the case of the simplicity, obeys a more general principle of economy, while in the case of the likelihood, it obeys a general principle of probability.

Nevertheless, these two terms might be only apparently different or may be considered as two sides or two different ways of considering the same visual process. Mach [20] suggested that vision acts in conformity with the principle of economy, and, at the same time, in conformity with the principle of probability. Chater [21] demonstrated mathematically that these key elements can be unified and considered equivalent within the theory of Kolmogorov complexity [22–27].

Feldman [28–31] presented a simplicity approach, called minimal model theory, and, in agreement with Chater [21], suggested that the visual interpretation, whose description is of minimum length, is the one that most likely is also the most veridical. Usually, the tendency of choosing a visual object that minimizes the description length is the same as the tendency of choosing a hypothesis that maximizes the likelihood. In brief, the most likely hypothesis about perceptual organization is, at the same time, the objects supporting the shortest description of the stimulus.

Far from this controversy, the point is here that we firmly reject van der Helm's attribution of a supposed general equivalence between the two principles.