•  170
    Editorial: PerceptualGrouping — The State of The Art
    Frontiers in Psychology 8 67. 2017.
    Perceptual neuroscience has identified mechanisms of perceptual grouping which account for the ways in which visual sensitivity to ordered structure and regularities expresses itself, in behavior and in the brain. The need to actively construct order, notably representations of objects in depth, is mandated as soon as visual signals reach the retina, given the occlusion of retinal signals by retinal veins and other retinal elements or blur. Multiple stages of neural processing transform fragment…Read more
  •  158
    The segregation of image parts into foreground and background is an important aspect of the neural computation of 3D scene perception. To achieve such segregation, the brain needs information about border ownership; that is, the belongingness of a contour to a specific surface represented in the image. This article presents psychophysical data derived from 3D percepts of figure and ground that were generated by presenting 2D images composed of spatially disjoint shapes that pointed inward o…Read more
  •  150
    Subthreshold Summation With Illusory Contours
    Vision Research 35 (8). 1994.
    Results from three experiments using spatial forced-choice techniques show that an illusory contour improves the detectability of a spatially superimposed, 1pixel-thin subthreshold line of either contrast polarity. Furthermore, the subthreshold line is found to enhance the visibility of an illusory contour bridging the gap between the two colinear edges of physically defined boundaries. Stimuli which do not induce illusory contours, but reduce uncertainty about the spatial position of the line, …Read more
  •  148
    The perception of brightness differences in Ehrenstein figures and of illusory contours in phase-shifted line gratings was investigated as a function of the contrast polarity of the inducing elements. We presented either continuous lines or line-like arrangements composed of aligned dashes or dots whose spacing was varied. A yes/no procedure was used in which naive observers had to decide whether or not they perceived a brightness difference in a given Ehrenstein figure or an illusory contour in…Read more
  •  148
    The rise of Artificial Intelligence (AI) has produced prophets and prophecies announcing that the age of artificial consciousness is near. Not only does the mere idea that any machine could ever possess the full potential of human consciousness suggest that AI could replace the role of God in the future, it also puts into question the fundamental human right to freedom and dignity. This position paper takes the stand that, in the light of all we currently know about brain evolution and the never…Read more
  •  143
    Grip force as a functional window to somatosensory cognition
    Frontiers in Psychology 13 1026439. 2022.
    Analysis of grip force signals tailored to hand and finger movement evolution and changes in grip force control during task execution provide unprecedented functional insight into somatosensory cognition. Somatosensory cognition is a basis of our ability to manipulate, move, and transform objects of the physical world around us, to recognize them on the basis of touch alone, and to grasp them with the right amount of force for lifting and manipulating them. Recent technology has permitted the wi…Read more
  •  141
    Occam's Razor For Big Data?
    Applied Sciences 3065 (9): 1-28. 2019.
    Detecting quality in large unstructured datasets requires capacities far beyond the limits of human perception and communicability and, as a result, there is an emerging trend towards increasingly complex analytic solutions in data science to cope with this problem. This new trend towards analytic complexity represents a severe challenge for the principle of parsimony (Occam’s razor) in science. This review article combines insight from various domains such as physics, computational science, dat…Read more
  •  141
    Two universal functional principles of Grossberg’s Adaptive Resonance Theory [19] decipher the brain code of all biological learning and adaptive intelligence. Low-level representations of multisensory stimuli in their immediate environmental context are formed on the basis of bottom-up activation and under the control of top-down matching rules that integrate high-level long-term traces of contextual configuration. These universal coding principles lead to the establishment of lasting brain sig…Read more
  •  138
    This article introduces an experimental paradigm to selectively probe the multiple levels of visual processing that influence the formation of object contours, perceptual boundaries, and illusory contours. The experiments test the assumption that, to integrate contour information across space and contrast sign, a spatially short-range filtering process that is sensitive to contrast polarity inputs to a spatially long-range grouping process that pools signals from opposite contrast polarities. Th…Read more
  •  136
    The biological significance of color
    with Keith Langley
    In D. Skusevich & P. Matikas (eds.), Color Perception: Physiology, Processes and Analysis, Nova Science Publishers. pp. 110--115. 2009.
    How the visual systems of different species enable them to detect and discriminate colour patterns and how such visual abilities contribute to their survival is discussed. The influence of evolutionary and environmental pressures on both perceptual capacity and colour trait production is to be considered. Visual systems with different functional anatomy have evolved in response to such pressures.
  •  135
    The quantization error in a fixed-size Self-Organizing Map (SOM) with unsupervised winner-take-all learning has previously been used successfully to detect, in minimal computation time, highly meaningful changes across images in medical time series and in time series of satellite images. Here, the functional properties of the quantization error in SOM are explored further to show that the metric is capable of reliably discriminating between the finest differences in local contrast intensities an…Read more
  •  132
    The thresholds of human observers detecting line targets improve significantly when the targets are presented in a spatial context of collinear inducing stimuli. This phenomenon is referred to as spatial facilitation, and may reflect the output of long-range interactions between cortical feature detectors. Spatial facilitation has thus far been observed with luminance-defined, achromatic stimuli on achromatic backgrounds. This study compares spatial facilitation with line targets and collinear, …Read more
  •  127
    A Plastic Temporal Code for Conscious State Generation
    Neural Plasticity 2009 (482696). 2009.
    Consciousness is known to be limited in processing capacity and often described in terms of a unique processing stream across a single dimension: time. In this paper, we discuss a purely temporal pattern code, functionally decoupled from spatial signals, for conscious state generation in the brain. Arguments in favour of such a code include Dehaene et al.'s long-distance reverberation postulate, Ramachandran's remapping hypothesis, evidence for a temporal coherence index and coincidence detector…Read more
  •  109
    Short- and long-range effects in line contrast integration
    Vision Research 42 2493-2498. 2002.
    Brincat and Westheimer [Journal of Neurophysiology 83 (2000) 1900] have reported facilitating interactions in the discrimination of spatially separated target orientations and co-linear inducing orientations by human observers. With smaller gaps between stimuli (short-range effects), facilitating interactions were found to depend on the contrast polarity of the stimuli. With larger gaps (longrange effects), only co-linearity of the stimuli seemed necessary to produce facilitation. In our study, …Read more
  •  100
    Two universal functional principles of Grossberg’s Adaptive Resonance Theory decipher the brain code of all biological learning and adaptive intelligence. Low-level representations of multisensory stimuli in their immediate environmental context are formed on the basis of bottom-up activation and under the control of top-down matching rules that integrate high-level, long-term traces of contextual configuration. These universal coding principles lead to the establishment of lasting brain signatu…Read more
  •  98
    Asymmetrical contrast effects induced by luminance and color configurations
    with Stéphane Fischer
    Perception and Psychophysics 63 (7): 1262-1270. 2001.
    In psychophysical experiments, the use of a psychophysical procedure of brightness/darkness cancellation shed light on interactions between spatial arrangement and figure–ground contrast in the perceptual filling in of achromatic and colored surfaces.Achromatic and chromatic Kanizsa squares with varying contrast, contrast polarity, and inducer spacingwere used to test how these factors interact in the perceptual filling in of surface brightness or darkness. The results suggest that the neuronal …Read more
  •  78
    The experience dependent dynamics of human consciousness
    Open Journal of Philosophy 8 (2): 116-143. 2018.
    By reviewing most of the neurobiology of consciousness, this article highlights some major reasons why a successful emulation of the dynamics of human consciousness by artificial intelligence is unlikely. The analysis provided leads to conclude that human consciousness is epigenetically determined and experience and context-dependent at the individual level. It is subject to changes in time that are essentially unpredictable. If cracking the code to human consciousness were possible, the result …Read more
  •  69
    Double, double, toil and trouble – fire burn, and theory bubble!
    Behavioral and Brain Sciences 26 (4): 409-410. 2003.
    Lehar's Gestalt Bubble model introduces a computational approach to holistic aspects of three-dimensional scene perception. The model as such has merit because it manages to translate certain Gestalt principles of perceptual organization into formal codes or algorithms. The mistake made in this target article is to present the model within the theoretical framework of the question of consciousness. As a scientific approach to the problem of consciousness, the Gestalt Bubble fails for several rea…Read more
  •  48
    The heuristic value of Pylyshyn's cognitive impenetrability theory is questioned in this commentary, mainly because, as it stands, the key argument cannot be challenged empirically. Pylyshyn requires unambiguous evidence for an effect of cognitive states on early perceptual mechanisms, which is impossible to provide because we can only infer what might happen at these earlier levels of processing on the basis of evidence collected at the post-perceptual stage. Furthermore, the theory that early …Read more
  •  42
    We question the ecological plausibility as a general model of cognition of van der Velde's & de Kamps's combinatorial blackboard architecture, where knowledge-binding in space and time relies on the structural rules of language. Evidence against their view of the brain and an ecologically plausible, alternative model of cognition are brought forward.
  •  41
    A simple working taxonomy with three classes of pictorial completion is proposed as an alternative to Pessoa et al.'s classification: area, surface, and contour completion. The classification is based on psychophysical evidence, not on the different phenomenal attributes of the stimuli, showing that pictorial completion is likely to involve mechanistic interactions in the visual system at different levels of processing. Whether the concept of “filling-in” is an appropriate metaphor for the visua…Read more
  •  34
    External regularities and adaptive signal exchanges in the brain
    Behavioral and Brain Sciences 24 (4): 663-664. 2001.
    Shepard's concept of internalization does not suggest mechanisms which help to understand how the brain adapts to changes, how representations of a steadily changing environment are updated or, in short, how brain learning continues throughout life. Neural mechanisms, as suggested by Barlow, may prove a more powerful alternative. Brain theories such as Adaptive Resonance Theory (ART) propose mechanisms to explain how representational activities may be linked in space and time. Some predictions o…Read more
  •  31
    Perceptual Categories Derived from Reid’s “Common Sense” Philosophy
    with Adam Reeves
    Frontiers in Psychology 8. 2017.
    The 18th-century Scottish ‘common sense’ philosopher Thomas Reid argued that perception can be distinguished on several dimensions from other categories of experience, such as sensation, illusion, hallucination, mental images, and what he called ‘fancy.’ We extend his approach to eleven mental categories, and discuss how these distinctions, often ignored in the empirical literature, bear on current research. We also score each category on five properties (ones abstracted from Reid) to form a 5 ×…Read more
  •  27
    The Kanizsa square does not engender a configural superiority effect
    Bulletin of the Psychonomic Society 31 (3): 183-184. 1993.
    This article presents psychophysical evidence that the Kanizsa Square does not produce an 'object superiority effect' previously reported in similar Gestalt configurations. Implications of the findings for Gestalt theory are addressed.