"Invariants" in Koffka's Theory of Constancies in Vision: Highlighting Their Logical Structure and Lasting Value

Summary By 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

Computational Modeling of Facial Response for Detecting Differential Traits in Autism Spectrum Disorders

This dissertation proposes novel computational modeling and computer vision methods for the analysis and discovery of differential traits in subjects with Autism Spectrum Disorders (ASD) using video and three-dimensional (3D) images of face and facial expressions. ASD is a neurodevelopmental disorder that impairs an individual’s nonverbal communication skills. This work studies ASD from the pathophysiology of facial expressions which may manifest atypical responses in the face. State-of-the-art psychophysical studies mostly employ na¨ıve human raters to visually score atypical facial responses of individuals with ASD, which may be subjective, tedious, and error prone. A few quantitative studies use intrusive sensors on the face of the subjects with ASD, which in turn, may inhibit or bias the natural facial responses of these subjects. This dissertation proposes non-intrusive computer vision methods to alleviate these limitations in the investigation for differential traits from the spontaneous facial responses of individuals with ASD. Two IRB-approved psychophysical studies are performed involving two groups of age-matched subjects: one for subjects diagnosed with ASD and the other for subjects who are typically-developing (TD). The facial responses of the subjects are computed from their facial images using the proposed computational models and then statistically analyzed to infer about the differential traits for the group with ASD. A novel computational model is proposed to represent the large volume of 3D facial data in a small pose-invariant Frenet frame-based feature space. The inherent pose-invariant property of the proposed features alleviates the need for an expensive 3D face registration in the pre-processing step. The proposed modeling framework is not only computationally efficient but also offers competitive performance in 3D face and facial expression recognition tasks when compared with that of the state-ofthe-art methods. This computational model is applied in the first experiment to quantify subtle facial muscle response from the geometry of 3D facial data. Results show a statistically significant asymmetry in specific pair of facial muscle activation (p\u3c0.05) for the group with ASD, which suggests the presence of a psychophysical trait (also known as an ’oddity’) in the facial expressions. For the first time in the ASD literature, the facial action coding system (FACS) is employed to classify the spontaneous facial responses based on facial action units (FAUs). Statistical analyses reveal significantly (p\u3c0.01) higher prevalence of smile expression (FAU 12) for the ASD group when compared with the TD group. The high prevalence of smile has co-occurred with significantly averted gaze (p\u3c0.05) in the group with ASD, which is indicative of an impaired reciprocal communication. The metric associated with incongruent facial and visual responses suggests a behavioral biomarker for ASD. The second experiment shows a higher prevalence of mouth frown (FAU 15) and significantly lower correlations between the activation of several FAU pairs (p\u3c0.05) in the group with ASD when compared with the TD group. The proposed computational modeling in this dissertation offers promising biomarkers, which may aid in early detection of subtle ASD-related traits, and thus enable an effective intervention strategy in the future

ON THE LOGIC, METHOD AND SCIENTIFIC DIVERSITY OF TECHNICAL SYSTEMS: AN INQUIRY INTO THE DIAGNOSTIC MEASUREMENT OF HUMAN SKIN

This dissertation explores some of the scientific, technical and cultural history of human skin measurement and diagnostics. Through a significant collection of primary texts and case studies, I track the changing technologies and methods used to measure skin, as well as the scientific and sociotechnical applications. I then map these histories onto some of the diverse understandings of the human body, physics, biology, natural philosophy and language that underpinned the scientific enterprise of skin measurement. The main argument of my thesis demonstrates how these diverse histories of science historically and theoretically inform the succeeding methods and applications for skin measurement from early Greek medicine, to beginnings of Anthropology as scientific discipline, to the emergence of scientific racism, to the age of digital imaging analysis, remote sensing, algorithms, massive databases and biometric technologies; further, these new digital applications go beyond just health diagnostics and are creating new technical categorizations of human skin divorced from the established ethical mechanisms of modern science. Based on this research, I inquire how communication practices within the scientific enterprise address the ethical and historical implications for a growing set of digital biometric applications with industrial, military, sociopolitical and public functions

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 341)

This bibliography lists 133 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during September 1990. Subject coverage includes: aerospace medicine and psychology, life support systems and controlled environments, safety equipment, exobiology and extraterrestrial life, and flight crew behavior and performance

Colour Communication Within Different Languages

For computational methods aiming to reproduce colour names that are meaningful to speakers of different languages, the mapping between perceptual and linguistic aspects of colour is a problem of central information processing. This thesis advances the field of computational colour communication within different languages in five main directions. First, we show that web-based experimental methodologies offer considerable advantages in obtaining a large number of colour naming responses in British and American English, Greek, Russian, Thai and Turkish. We continue with the application of machine learning methods to discover criteria in linguistic, behavioural and geometric features of colour names that distinguish classes of colours. We show that primary colour terms do not form a coherent class, whilst achromatic and basic classes do. We then propose and evaluate a computational model trained by human responses in the online experiment to automate the assignment of colour names in different languages across the full three-dimensional colour gamut. Fourth, we determine for the first time the location of colour names within a physiologically-based cone excitation space through an unconstrained colour naming experiment using a calibrated monitor under controlled viewing conditions. We show a good correspondence between online and offline datasets; and confirm the validity of both experimental methodologies for estimating colour naming functions in laboratory and real-world monitor settings. Finally, we present a novel information theoretic measure, called dispensability, for colour categories that predicts a gradual scale of basicness across languages from both web- and laboratory- based unconstrained colour naming datasets. As a result, this thesis contributes experimental and computational methodologies towards the development of multilingual colour communication schemes

Enlightened Romanticism: Mary Gartside’s colour theory in the age of Moses Harris, Goethe and George Field

The aim of this paper is to evaluate the work of Mary Gartside, a British female colour theorist, active in London between 1781 and 1808. She published three books between 1805 and 1808. In chronological and intellectual terms Gartside can cautiously be regarded an exemplary link between Moses Harris, who published a short but important theory of colour in the second half of the eighteenth century, and J.W. von Goethe’s highly influential Zur Farbenlehre, published in Germany in 1810. Gartside’s colour theory was published privately under the disguise of a traditional water colouring manual, illustrated with stunning abstract colour blots (see example above). Until well into the twentieth century, she remained the only woman known to have published a theory of colour. In contrast to Goethe and other colour theorists in the late 18th and early 19th century Gartside was less inclined to follow the anti-Newtonian attitudes of the Romantic movement

NICE : A Computational solution to close the gap from colour perception to colour categorization

The segmentation of visible electromagnetic radiation into chromatic categories by the human visual system has been extensively studied from a perceptual point of view, resulting in several colour appearance models. However, there is currently a void when it comes to relate these results to the physiological mechanisms that are known to shape the pre-cortical and cortical visual pathway. This work intends to begin to fill this void by proposing a new physiologically plausible model of colour categorization based on Neural Isoresponsive Colour Ellipsoids (NICE) in the cone-contrast space defined by the main directions of the visual signals entering the visual cortex. The model was adjusted to fit psychophysical measures that concentrate on the categorical boundaries and are consistent with the ellipsoidal isoresponse surfaces of visual cortical neurons. By revealing the shape of such categorical colour regions, our measures allow for a more precise and parsimonious description, connecting well-known early visual processing mechanisms to the less understood phenomenon of colour categorization. To test the feasibility of our method we applied it to exemplary images and a popular ground-truth chart obtaining labelling results that are better than those of current state-of-the-art algorithms

Multisensory learning in adaptive interactive systems

The main purpose of my work is to investigate multisensory perceptual learning and sensory integration in the design and development of adaptive user interfaces for educational purposes. To this aim, starting from renewed understanding from neuroscience and cognitive science on multisensory perceptual learning and sensory integration, I developed a theoretical computational model for designing multimodal learning technologies that take into account these results. Main theoretical foundations of my research are multisensory perceptual learning theories and the research on sensory processing and integration, embodied cognition theories, computational models of non-verbal and emotion communication in full-body movement, and human-computer interaction models. Finally, a computational model was applied in two case studies, based on two EU ICT-H2020 Projects, "weDRAW" and "TELMI", on which I worked during the PhD

Low-level visual processing and its relation to neurological disease

Retinal neurons extract changes in image intensity across space, time, and wavelength. Retinal signal is transmitted to the early visual cortex, where the processing of low-level visual information occurs. The fundamental nature of these early visual pathways means that they are often compromised by neurological disease. This thesis had two aims. First, it aimed to investigate changes in visual processing in response to Parkinson’s disease (PD) by using electrophysiological recordings from animal models. Second, it aimed to use functional magnetic resonance imaging (fMRI) to investigate how low-level visual processes are represented in healthy human visual cortex, focusing on two pathways often compromised in disease; the magnocellular pathway and chromatic S-cone pathway. First, we identified a pathological mechanism of excitotoxicity in the visual system of Drosophila PD models. Next, we found that we could apply machine learning classifiers to multivariate visual response profiles recorded from the eye and brain of Drosophila and rodent PD models to accurately classify these animals into their correct class. Using fMRI and psychophysics, found that measurements of temporal contrast sensitivity differ as a function of visual space, with peripherally tuned voxels in early visual areas showing increased contrast sensitivity at a high temporal frequency. Finally, we used 7T fMRI to investigate systematic differences in achromatic and S-cone population receptive field (pRF) size estimates in the visual cortex of healthy humans. Unfortunately, we could not replicate the fundamental effect of pRF size increasing with eccentricity, indicating complications with our data and stimulus

Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task