Previously published studies have reported that 150 min of short-term monocular deprivation temporarily changes perceptual eye dominance. However, the possible mechanisms underlying monocular deprivation-induced perceptual eye dominance plasticity remain unclear. Using a binocular phase and contrast co-measurement task and a multi-pathway contrast-gain control model, we studied the effect of 150 min of monocular pattern deprivation in normal adult subjects. The perceived phase and contrast varied significantly with the interocular contrast ratio, and after MPD, the patched eye became (...) dominant. Most importantly, we focused on the potential mechanisms of the deprivation effect. The data of an averaged subject was best fitted by a model, which assumed a monocular signal enhancement of the PE after the MPD. The present findings might have important implications for investigations of binocular vision in both normal and amblyopic populations. (shrink)

Psychologically faithful deep neural networks (DNNs) could be constructed by training with psychophysics data. Moreover, conventional DNNs are mostly monocular vision based, whereas the human brain relies mainly on binocular vision. DNNs developed as smaller vision agent networks associated with fundamental and less intelligent visual activities, can be combined to simulate more intelligent visual activities done by the biological brain.

In a recent article on Reid’s theory of single and double vision, James Van Cleve considers an argument against direct realism presented by Hume. Hume argues for the mind-dependent nature of the objects of our perception from the phenomenon of double vision. Reid does not address this particular argument, but Van Cleve considers possible answers Reid might have given to Hume. He finds fault with all these answers. Against Van Cleve, I argue that both appearances in double (...) class='Hi'>vision could be considered visible figures of the object, and show how this solution might preserve Reid’s direct realism. However, this solution is not compatible with the single appearance of an object predicted by Reid’s theory of single and double vision. This consequence will appear evident once we consider the critique of Reid’s theory of single and double vision formulated by William Charles Wells (1757-1817). Wells argues that Reid’s theory is either incomplete or incompatible with other claims made by Reid. It is incomplete since it fails to specify the unique direction in which we the object in single vision; if it not incomplete and is compatible with the law of monocular direction given by Reid, then it is incompatible with Reid’s claim that we do not perceive immediately distance by sight. (shrink)

Previous studies have demonstrated that orientation-specific deprivation in early life can lead to neural deficits of spatial vision in certain space, and can even result in meridional amblyopia. Individuals with astigmatism are the optimal and natural models for exploring this asymmetric development of spatial vision in the human visual system. This study aims to assess the contrast sensitivity function and EEG signals along two principal meridians in participants with regular astigmatism when being optimal optical corrected. Twelve participants with (...) astigmatism and thirteen participants with were recruited in the current study. CSFs and spatial sweep visual evoked potentials were measured with vertical and horizontal sinewave gratings along two principal meridians monocularly. Area under log CSF, spatial frequency threshold corresponding to 80% contrast gratings, and CSF acuity were calculated from CSF test. In addition, sVEP amplitudes and thresholds were calculated with the recursive least square method. Participants with astigmatism exhibited marked vertical-horizontal resolution disparities even after they were corrected with optimal optical corrections. CSF tests showed that AULCSF along weak meridian was lower than that along strong meridian in both groups. Significant meridional disparity of CSF acuity was also found in both groups. In addition, the MA group showed larger meridional disparity compared to the AST group. Spatial sVEP thresholds also supported the existence of marked meridional disparity. Our results suggest that meridian-specific partial deprivation in early life might lead to monocularly asymmetric development of spatial vision in the human visual system. In terms of application, we tested the feasibility and reliability of adopting psychophysical and EEG scalings to investigate the asymmetric development of spatial vision related to astigmatism. These paradigms are potentially applicable to reduce and even eliminate the meridional disparity in the primary visual cortex by adopting perceptual learning or other vision-related interventions. (shrink)

In this article, we present our work to provide a navigation and localization system on a constrained humanoid platform, the NAO robot, without modifying the robot sensors. First, we tried to implement a simple and light version of classic monocular Simultaneous Localization and Mapping algorithms, while adapting to the CPU and camera quality, which turned out to be insufficient on the platform for the moment. From our work on keypoints tracking, we identified that some keypoints can be still accurately (...) tracked at little cost, and used them to build a visual compass. This compass was then used to correct the robot walk because it makes it possible to control the robot orientation accurately. (shrink)

We show that early vision can use monocular cues to rapidly complete partially-occluded objects. Visual search for easily detected fragments becomes difficult when the completed shape is similar to others in the display; conversely, search for fragments that are difficult to detect becomes easy when the completed shape is distinctive. Results indicate that completion occurs via the occlusion-triggered removal of occlusion edges and linking of associated regions. We fail to find evidence for a visible filling-in of contours or (...) surfaces, but do find evidence for a "functional" filling-in that prevents the constituent fragments from being rapidly accessed. As such, it is only the completed structures—and not the fragments themselves—that serve as the basis for rapid recognition. (shrink)

Visualizing and mental imagery are thought to be cognitive states by all sides of the imagery debate. Yet the phenomenology of those states has distinctly visual ingredients. This has potential consequences for the hypothesis that vision is cognitively impenetrable, the ability of visual processes to ground perceptual warrant and justification, and the distinction between cognitive and perceptual phenomenology. I explore those consequences by describing two forms of visual ambiguity that involve visualizing: the ability to visually experience a picture surface (...) as flat after it has caused volumetric nonconceptual contents, and the ability to use a surface initially perceived as flat to visualize three-dimensional scenes. In both cases, the visual processes which extract viewer-centered volumetric shapes have to rely solely on monocular depth cues in the absence of parallax and stereopsis. Those processes can be cognitively penetrated by acts of visualizing, including ones that draw on conceptual information about kinds. However, the penetrability of the visual processes does not weaken their ability to provide perceptual warrant and justification for beliefs. The reason is that picture perceptions—whether they are stimulus -driven or based on acts of visualizing—are different to object perceptions both phenomenologically and in terms of their functional roles as states. Thus, although the penetrability of the visual processes does mean that subjects can have visual experiences with contradictory contents, perceptual belief is adopted at most towards one set of contents, and questions of warrant and justification are raised only for those contents. A rule-proving exception is provided by trompe-l’oeils. (shrink)

This paper presents an autonomous vision-based obstacle avoidance system. The system consists of three independent vision modules for obstacle detection, each of which is computationally simple and uses a di erent criterion for detection purposes. These criteria are based on brightness gradients, RGB Red, Green, Blue color, and HSV Hue, Saturation, Value color, respectively. Selection of which modules are used to command the robot proceeds exclusively from the outputs of the modules themselves. The system is implemented on a (...) small monocular mobile robot and uses very low resolution images. It has been tested for over 200 hours in diverse environments. Keywords: Vision-based navigation, space exploration, modular design, reactive control, unstructured terrain. (shrink)

In the Quattrocento and Cinquecento the rise of linear perspective caused many polemics which opposed the supporters of an artificial geometrisation of sight to those who were praising the qualities of the drawing according to nature, or were invoking some arguments on a physiological basis. These debates can be grouped according to the four alternatives that form their central concerns: restricted vs. broad field of vision; ocular immobility vs. mobility; curvilinear vs. planar picture; monocular vs. binocular vision. (...) By retaining the first terms of these four alternatives, the history of perspective eliminated many heterodox constructions. From the viewpoint of mathematisation the interest of these debates is that they succeeded, rather than preceded, the adoption of a perspective system defined by the intersection of the visual pyramid. Thus the history of linear perspective constitutes a genuine case of a posteriori justification, or, put differently, it gives us a case of upside down mathematisation. (shrink)

Delay in seeking medical services is common in elderly populations, which leads to disease progression and life difficulty. This study aims to assess the prevalence of delay in medical visits and treatment and define associated effects and factors in patients with senile cataract, which may help obtain a better understanding of late-life psychopathology and provide the basis for interventions. Patients aged more than 60 years were prospectively recruited in Zhongshan Ophthalmic Center. All participants were diagnosed with binocular senile cataract and (...) decided to have primary surgery in ZOC. The distributions of the popularity of delaying outpatient visits and treatment, the degrees of visual impairment, the influences on quality of life, and the reasons for delaying treatment among participants were accessed by the descriptive statistics. Factors associated with the perceptions of cataract treatment were accessed using a binary logistic regression model. A total of 400 senile patients aged from 60 to 94 years were enrolled. At diagnosis, 82 participants had a low vision with monocular acuity of both eyes below 0.05. All participants have felt that their normal lives were affected, and 64 participants felt that their lives were affected severely. Only 17 participants have sought for medical services immediately after feeling vision loss, and 294 participants have felt vision loss since a year ago before seeking medical help. A total of 298 participants have delayed the surgery time, and 229 patients delayed it for more than 12 months. There were 147 participants delaying surgery on account of no knowledge about it and 114 participants delaying surgery because of fear. There are a high proportion of elderly patients with senile cataract delaying their outpatient visits and surgery treatment, whose normal lives were severely affected. Increasing medical service propaganda about cataract and other common diseases in elderly populations would probably be helpful for improving perceptions of diseases and decreasing medical delays. Public needs to draw more attention to the healthy and medical status of the elderly ocular patients. (shrink)

Little is known about distance processing in patients with posterior brain damage. Although many investigators have claimed that distance estimates are normal or abnormal in some of these patients, many of these observations were made informally and the examiners often asked for relative, and not absolute, distance estimates. The present investigation served two purposes. First, we wanted to contrast the use of distance information in peripersonal space for perceptual report as opposed to visuomotor control in our visual form agnosic patient, (...) DF. Second, we wanted to see to what extent her abilities to process distance cues were dependent on binocular vision, in light of Milner et al.'s (1991) observations of preserved stereopsis in DF, and Dijkerman et al.'s (1996) and Marotta et al.'s (1997) observations that her visual guidance of grasping may be particularly dependent on binocular vision of the target. We hypothesized that DF's visuomotor responses would show normal sensitivity to target distance, while her perceptual estimates would not. In the first experiment, we required DF and two age- and sex-matched control subjects to reach out and grasp black cubes placed at varying distances, or to estimate the distance of the cubes from the hand starting position without making a reaching movement. In the second experiment, we required DF and two age-matched control subjects to point as rapidly and accurately as possible to small LED targets which differed in spatial location, under binocular and monocular conditions. The results showed that, relative to the control subjects, DF's grasping movements produced normal peak velocity-distance scaling-when she reached for blocks which varied in depth or pointed to LED targets which were presented at different distances in depth. In contrast, in the cube experiment, her verbal estimates of object distance were poorly scaled, although they improved slightly under the binocular conditions. The results are discussed in terms of current theories of processing streams in extrastriate visual cortex and the distinction between categorical and coordinate spatial processing. (shrink)

The relationship between brain activity and conscious visual experience is central to our understanding of the neural mechanisms underlying perception. Binocular rivalry, where monocular stimuli compete for perceptual dominance, has been previously used to dissociate the constant stimulus from the varying percept. We report here fMRI results from humans experiencing binocular rivalry under a dichoptic stimulation paradigm that consisted of two drifting random dot patterns with different motion coherence. Each pattern had also a different color, which both enhanced rivalry (...) and was used for reporting which of the two patterns was visible at each time. As the perception of the subjects alternated between coherent motion and motion noise, we examined the effect that these alternations had on the strength of the MR signal throughout the brain. Our results demonstrate that motion perception is able to modulate the activity of several of the visual areas which are known to be involved in motion processing. More specifically, in addition to area V5 which showed the strongest modulation, a higher activity during the perception of motion than during the perception of noise was also clearly observed in areas V3A and LOC, and less so in area V3. In previous studies, these areas had been selectively activated by motion stimuli but whether their activity reflects motion perception or not remained unclear; here we show that they are involved in motion perception as well. The present findings therefore suggest a lack of a clear distinction between ?processing? versus ?perceptual? areas in the brain, but rather that the areas involved in the processing of a specific visual attribute are also part of the neuronal network that is collectively responsible for its perceptual representation. (shrink)

In this book Gerald Vision argues for a new causal theory, one that engages provocatively with direct realism and makes no use of a now discredited subjectivism.

In Veritas, Gerald Vision defends the correspondence theory of truth -- the theory that truth has a direct relationship to reality -- against recent attacks, and critically examines its most influential alternatives. The correspondence theory, if successful, explains one way in which we are cognitively connected to the world; thus, it is claimed, truth -- while relevant to semantics, epistemology, and other studies -- also has significant metaphysical consequences. Although the correspondence theory is widely held today, Vision points (...) to an emerging orthodoxy in philosophy that claims that truth as such carries no significant weight in philosophical explanations. He devotes much of the book to a criticism of that outlook and to a less vulnerable formulation of the correspondence theory.Vision defends the correspondence theory by both presenting evidence for correspondence and examining the claims made by such alternative theories as deflationism, minimalism, and pluralism. The techniques of the argument are thoroughly analytic, but the problem confronted is broadly humanistic. The question examined -- how we, as thinking beings, are connected to and manage to cope in a world that was not designed for our comfort or convenience -- is more likely to be raised by continentalists, but is approached here with the tools of clarity and precision more highly prized in analytic philosophy. The book seeks to avoid both the obscurantism that infects much continental thought and the overly technical concerns and methodology that limit the interest of much work in analytic philosophy. It thus provides a rigorous but largely nontechnical treatment of the topic that will be of interest not only to readers familiar with philosophy but also to those with a background in literary theory and linguistics. (shrink)

The evidence of blindsight is occasionally used to argue that we can see things, and thus have perceptual belief, without the distinctive visual awareness accompanying normal sight; thereby displacing phenomenality as a component of the concept of vision. I maintain that arguments to this end typically rely on misconceptions about blindsight and almost always ignore associated visual (or visuomotor) pathologies relevant to the lessons of such cases. More specifically, I conclude, first, that the phenomena very likely do not result (...) from dissociations within a single system, but from the interaction of evolutionarily distinct, if interacting, systems; second, that a closer study of spared motor abilities indicates that verbal responses of patients result not from degraded vision but from proprioception; and, finally, above chance verbal responses, being forced guesses, are not tentative beliefs and cannot become beliefs just by training patients to have more confidence in their responses. (shrink)

I INTRODUCTION - THE TOPIC EXPLAINED 1 GENERAL DIFFERENCES From its inception to the present, philosophy may be viewed as a series of struggles between ...

In virtue of its form [‘I am here’] must be true on any occasion on which [it is] asserted, and yet the proposition it expresses on each occasion [is] contingent. Intuitively, [‘I am here now’] is deeply, and in some sense universally, true. One need only understand the meaning of [it] to know that it cannot be uttered falsely. The sentence ‘I am here’ has the peculiar property that whenever I utter it, it is bound to be true. Even if (...) I am lost and do not know where I am, I can bravely say ‘I am here’, and know that I am expressing a truth. (shrink)

In " Re-Emergence" he explores the question of conscious properties arising from brute, unthinking matter, making the case that there is no equally plausible non-emergent alternative.

Parmenides didn't mention reference as such, but if he had he would have undoubtedly agreed with the philosophers who nowadays hold what is called "the axiom of existence": that one can only refer to what exists. The sources of possible support for this view are examined and rejected. Primary support for the axiom is given by two sorts of argument; one concerning quantification, the other summarizing a standard Parmenidean puzzle. Weaknesses in both are exposed. Finally, the relations between the axiom (...) and connected claims about predication and truth are probed, and an attempt is made to determine the limits of the mutual support these claims give one another. (shrink)

Under the title of ‘the axiom of existence’, hereafter, John R. Searle has reduced to compact dictum a view to which many philosophers subscribe: ‘Whatever is referred to must exist’. In this paper I shall offer two major arguments against adopting, at least on certain assumptions. There have been a number of defenses of, among them those arguing that it is fundamental to any systematic philosophy of language or logic. With the exception of discussing some of Searle's remarks in part (...) Ill of this paper I shall not comment on any of these defenses. (shrink)

A very material question has been started concerning abstract or general ideas, whether they be general or particular in the mind's conception of them. A great philosopher [Dr. Berkeley] has disputed the receiv'd opinion in this particular, and has asserted, that all general ideas are nothing but particular ones, annexed to a certain term, which gives them a more extensive signification, and makes them recall upon occasion other individuals, which are similar to them. As I look upon this to be (...) one of the greatest and most valuable discoveries that has been made of late years in the republic of letters, I shall here endeavour to confirm it by some arguments, which I hope will put it beyond all doubt and controversy. (shrink)

Interjections, such as those in the title, together with a few similar devices, when qualifying clauses expressing truth-conditions, or that such conditions have been satisfied, are entitled 'force-amplifiers'. Disputes between deflationary and inflationary truth-theories sometimes are assumed to turn on the supposed pivotal role that these devices are construed as playing in the interpretation of the clauses they qualify. I argue that they are not dispensable add-ons. Moreover, even in their absence the relevant clauses giving truth-conditions permit interpretations that are (...) not deflationary-friendly. I maintain that this is a significant fact about the use to which writers put them. I then defend, a thesis about force-amplifiers that makes them indispensable to the interpretation of the relevant clauses, and that renders certain moves unavailable to popular deflationist treatments. (shrink)