Capacity of using visual feedback by infants at the age of reaching onset has been controversial. In this investigation we assessed movement kinematics in the task of reaching for a toy in 5-month-olds, comparing movements performed with the preferred arm under full vision versus visual occlusion. That comparison was made in consecutive periods of visual occlusion. Analysis of results revealed that visual occlusion led to decreased straightness of arm displacement toward the toy as compared to full vision. Longer periods (...) of occlusion did not augment that effect. These results offer preliminary evidence for use of visual feedback early in infants’ reaching development. Reconciliation of previous and current findings is made by proposing a hybrid mode of feedback processing for manual control reweighting the roles of vision and proprioception as a function of availability of environmental information. (shrink)
While performing an action, the timing of when the sensory feedback is given can be used to establish the causal link between the action and its consequence. It has been shown that delaying the visual feedback while carrying an object makes people feel the mass of the object to be greater, suggesting that the feedback timing can also impact the perceived quality of an external object. In this study, we investigated the origin of the feedback timing (...) information that influences the mass perception of the external object. Participants made a straight reaching movement while holding a manipulandum. The movement of the manipulandum was presented as a cursor movement on a monitor. In Experiment 1, various delays were imposed between the actual trajectory and the cursor movement. The participants’ perceived mass of the manipulandum significantly increased as the delay increased to 400 ms, but this gain did not reach significance when the delay was 800 ms. This suggests the existence of a temporal tuning mechanism for incorporating the visual feedback into the perception of mass. In Experiment 2, we examined whether the increased mass perception during the visual delay was due to the prediction error of the visual consequence of an action or to the actual delay of the feedback itself. After the participants adapted to the feedback delay, the perceived mass of the object became lighter than before, indicating that updating the temporal prediction model for the visual consequence diminishes the overestimation of the object’s mass. We propose that the misattribution of the visual delay into mass perception is induced by the sensorimotor prediction error, possibly when the amount of delay (error) is within the range that can reasonably include the consequence of an action. (shrink)
Neurophysiological investigations of the visual system by way of single-cell recordings have revealed a hierarchical architecture in which lower level areas, such as the primary visual cortex, contain cells that respond to simple features, while higher level areas contain cells that respond to higher order features apparently composed of combinations of lower level features. This architecture seems to suggest a feed-forward processing strategy in which visual information progresses from lower to higher visual areas. However there is other evidence, both neurophysiological (...) and phenomenal, that suggests a more parallel processing strategy in biological vision, in which top-down feedback plays a significant role. In fact Gestalt theory suggests that visual perception involves a process of emergence, i.e. a dynamic relaxation of multiple constraints throughout the system simultaneously, so that the final percept represents a stable state, or energy minimum of the dynamic system as a whole. A Multi-Level Reciprocal Feedback (MLRF) model is proposed to resolve the apparently contradictory concepts, by proposing a hierarchical visual architecture whose different levels are connected by bi-directional feed-forward and feedback pathways, where the computational transformation performed by the feedback pathway between levels in the hiararchy is a kind of inverse of the transformation performed by the corresponding feed-forward processing stream. This alternative paradigm of perceptual computation accounts in general terms for a number of visual illusory effects, and offers a computational specification for the generative, or constructive aspect of perceptual processing revealed by Gestalt theory. (shrink)
Recent developments in psychology and neuroscience suggest away to link the mental phenomenon of visual awareness with specific neural processes. Here, it is argued that the feed-forward activation of cells in any area of the brain is not sufficient to generate awareness, but that recurrent processing, mediated by horizontal and feedback connections is necessary. In linking awareness with its neural mechanisms it is furthermore important to dissociate phenomenal awareness from visual attention or decision processes.
The present description of the Merge model addresses only auditory, not audiovisual, speech perception. However, recent findings in the audiovisual domain are relevant to the model. We outline a test that we are conducting of the adequacy of Merge, modified to accept visual information about articulation.
Objects in our visual environment are arranged in depth and hence there is a considerable amount of overlap and occlusion in the image they generate on the retina. In order to properly segment the image into fi gure and background, boundary interpolation is required even across large distances. Here we study the cortical mechanisms involved in collinear contour interpolation using fMRI. Human observers were asked to discriminate the curvature of interpolated boundaries in Kanizsa fi gures and in control confi gurations, (...) which contained identical physical information but did not generated subjective shapes. We measured a spatially precise spin-echo BOLD signal and found stronger responses to subjective shapes than non-shapes at the subjective boundary locations, but not at the inducer locations. The responses to subjective contours within primary visual cortex were retinotopically specifi c and analogous to that to real contours, which is intriguing given that subjective and luminance-defi ned contours are physically fundamentally different. We suggest that in the absence of retinal stimulation, the observed activation changes in primary visual cortex are driven by intracortical interactions and feedback, which are revealed in the absence of a physical stimulus. (shrink)
How does the brain bind together visual features that are processed concurrently by different neurons into a unified percept suitable for processes such as object recognition? Here, we describe how simple, commonly accepted principles of neural processing can interact over time to solve the brain's binding problem. We focus on mechanisms of neural inhibition and top-down feedback. Specifically, we describe how inhibition creates competition among neural populations that code different features, effectively suppressing irrelevant information, and thus minimizing illusory conjunctions. (...) Top-down feedback contributes to binding in a similar manner, but by reinforcing relevant features. Together, inhibition and top-down feedback contribute to a competitive environment that ensures only the most appropriate features are bound together. We demonstrate this overall proposal using a biologically realistic neural model of vision that processes features across a hierarchy of interconnected brain areas. Finally, we argue that temporal synchrony plays only a limited role in binding -- it does not simultaneously bind multiple objects, but does aid in creating additional contrast between relevant and irrelevant features. Thus, our overall theory constitutes a solution to the binding problem that relies only on simple neural principles without any binding-specific processes. (shrink)
Humans are remarkably proficient at categorizing visually-similar objects. To better understand the cortical basis of this categorization process, we used magnetoencephalography (MEG) to record neural activity while participants learned--with feedback--to discriminate two highly-similar, novel visual categories. We hypothesized that although prefrontal regions would mediate early category learning, this role would diminish with increasing category familiarity and that regions within the ventral visual pathway would come to play a more prominent role in encoding category-relevant information as learning progressed. Early in (...) learning we observed some degree of categorical discriminability and predictability in both the prefrontal cortex and the ventral visual pathway. Predictability improved significantly above chance in the ventral visual pathway over the course of learning with the left inferiortemporal and fusiform gyri showing the greatest improvement in predictability between 150-250msec (M200) during category learning. In contrast, there was no comparable increase in discriminability in prefrontal cortex with the only significant post-learning effect being a decrease in predictability in inferior frontal gyrus between 250-350msec (M300). Thus, the ventral visual pathway appears to encode learned visual categories over the long term. At the same time these results add to our understanding of the cortical origins of previously-reported signature temporal components associated with perceptual learning. (shrink)
The Social Simon effect (SSE) occurs if two participants share a Simon task by making a Go/No-Go response to one of two stimulus features. If the two participants perform this version of the Simon task together, a Simon effect occurs (i.e., performance is better with spatial stimulus-response correspondence), but no effect is observed if participants perform the task separately. The SSE has been attributed to the automatic co-representation of the co-actor’s actions, which suggests that it relies on online information about (...) the other’s actions. To test this implication, we investigated whether the SSE varies with the presence and amount of online action-related feedback from the other person. Experiment 1 replicated the SSE with auditory stimuli. Experiment 2, in which participants were blindfolded, demonstrated that visual feedback from the other’s actions is not necessary for the SSE to occur. Experiment 3 replicated Experiment 2 with a regular and a soundless keyboard. A comparable SSE was obtained in both conditions, suggesting that even auditory online input from the other’s actions is not necessary. Taken together, our data suggest that the SSE does not rely on online information about the co-actor’s actions but that a priori offline information about the other’s mere presence is sufficient to generate the effect. (shrink)
Previous studies have demonstrated a great uncertainty in evaluating one's own voluntary actions when visual feedback is suspended. We now compare these limitations in younger and older adults during active or passive limb movements. Participants put their dominant hand on a robot arm and performed movements actively or the relaxed limb was moved passively. Either a distorted visual feedback or no visual feedback at all was provided during the movement. Perception of limb movements was attenuated through visual (...)feedback. This effect was more pronounced in older adults. However, no difference between active and passive movements was found. The results provide evidence for the limited awareness of body effects, even in the absence of voluntary actions. (shrink)
Evidence from many different paradigms (e.g. change blindness, inattentional blindness, transsaccadic integration) indicate that observers are often very poor at reporting changes to their visual environment. Such evidence has been used to suggest that the spatio-temporal coherence needed to represent change can only occur in the presence of focused attention. In four experiments we use modified change blindness tasks to demonstrate (a) that sensitivity to change does occur in the absence of awareness, and (b) this sensitivity does not rely on (...) the redeploy- ment of attention. We discuss these results in relation to theories of scene percep- tion, and propose a reinterpretatio n of the role of attention in representing change. (shrink)
Argues for a category of “cognitive feelings”, which are representationally significant, but are not part of the content of the states they accompany. The feeling of pastness in episodic memory, of familiarity (missing in Capgras syndrome), and of motivation (that accompanies desire) are examples. The feeling of presence that accompanies normal visual states is due to such a cognitive feeling; the “two visual systems” are partially responsible for this feeling.
Often implicit in visual display design and development is a gold standard of photorealism. By approximating direct perception, photorealism appeals to users and designers by being both attractive and apparently effortless. The vexing result from numerous performance evaluations, though, is that increasing realism often impairs performance. Smallman and St. John (2005) labeled misplaced faith in realistic information display Naïve Realism and theorized it resulted from a triplet of folk fallacies about perception. Here, we illustrate issues associated with the wider trend (...) towards realism by focusing on a specific current trend for high-fidelity perspective view (3D) geospatial displays. In two experiments, we validated Naïve Realism for different terrain understanding tasks, explored whether certain individuals are particularly prone to Naïve Realism, and determined the ability of task feedback to mitigate Naïve Realism. Performance was measured for laying and judging a concealed route across realistic terrain shown in different display formats. Task feedback was either implicit, in Experiment 1, or explicit in Experiment 2. Prospective and retrospective intuitions about the best display formats for the tasks were recorded and then related to task performance and participant spatial ability. Participants generally intuited they would perform tasks better with more realism than they actually required. For example, counter to intuitions, lowering fidelity of the terrain display revealed the gross scene layout needed to lay a well-concealed route. Individuals of high spatial ability calibrated their intuitions with only implicit task feedback, whereas those of low spatial ability required salient, explicit feedback to calibrate their intuitions about display realism. Results are discussed in the wider context of applying perceptual science to display design, and combating folk fallacies. (shrink)
The authors O'Regan & Noë (O&N) have ignored the case for the visual field as being non-epistemic evidence internal to the brain, having no pictorial similarity to the external input, and being material in ontological status. They are also not aware of the case for the evolutionary advantage of learning as the perceptual refashioning of such non-epistemic sensory evidence via motivated feedback in sensorimotor activity.
Many philosophers have held that it is not possible to experience a spatial object, property, or relation except against the background of an intact awareness of a space that is somehow ‘absolute’. This paper challenges that claim, by analyzing in detail the case of a brain-damaged subject whose visual experiences seem to have violated this condition: spatial objects and properties were present in his visual experience, but space itself was not. I go on to suggest that phenomenological argumentation can give (...) us a kind of evidence about the nature of the mind even if this evidence is not absolutely incorrigible. (shrink)
A common objection to representationalism is that a representationalist view of phenomenal character cannot accommodate the effects that shifts in covert attention have on visual phenomenology: covert attention can make items more visually prominent than they would otherwise be without altering the content of visual experience. Recent empirical work on attention casts doubt on previous attempts to advance this type of objection to representationalism and it also points the way to an alternative development of the objection.
Milner and Goodale’s influential account of the primate cortical visual streams involves a division of consciousness between them, for it is the ventral stream that has the responsibility for visual consciousness. Hence, the dorsal visual stream is a “zombie” stream. In this paper, I argue that certain information carried by the dorsal stream likely plays a central role in the egocentric spatial content of experience, especially the experience of visual spatial constancy. Thus, the dorsal stream contributes to a pervasive feature (...) of consciousness. (shrink)
The two contrasting theoretical approaches to visual perception, the constructivist and the ecological, are briefly presented and illustrated through their analyses of space and size perception. Earlier calls for their reconciliation and unification are reviewed. Neurophysiological, neuropsychological, and psychophysical evidence for the existence of two quite distinct visual systems, the ventral and the dorsal, is presented. These two perceptual systems differ in their functions; the ventral system's central function is that of identification, while the dorsal system is mainly engaged in (...) the visual control of motor behavior. The strong parallels between the ecological approach and the functioning of the dorsal system, and between the constructivist approach and the functioning of the ventral system are noted. It is also shown that the experimental paradigms used by the proponents of these two approaches match the functions of the respective visual systems. A dual-process approach to visual perception emerges from this analysis, with the ecological-dorsal process transpiring mainly without conscious awareness, while the constructivist-ventral process is normally conscious. Some implications of this dual-process approach to visual-perceptual phenomena are presented, with emphasis on space perception. Key Words: constructivist; dual-process approach; ecological; size perception; space perception; two visual systems; visual perception theories. (shrink)
Pictorial representation is one species of visual representation--but not the only one, I argue. There are three additional varieties or species of visual representation--namely 'structural', 'aspect' and 'integrative' representation--which together comprise a category of 'delineative' rather than depictive visual representation. I arrive at this result via consideration of previously neglected orientational factors that serve to distinguish the two categories. I conclude by arguing that pictures (unlike 'delineations') are not physical objects, and that their multiplicity and modal narrowness motivates a view (...) of them as instead being (one kind of) 'delineatively' represented content or subject matter, as represented by those objects that are (commonly but wrongly, in my view) assumed to be pictures. (shrink)
determinacy is the claim that covert shifts in visual attention sometimes affect the determinacy of visual content (capital letters will distinguish the claim from the familiar word, ?determinacy?). Representationalism is the claim that visual phenomenology supervenes on visual representational content. Both claims are popular among contemporary philosophers of mind, and determinacy has been employed in defense of representationalism. I claim that existing arguments in favor of determinacy are inconclusive. As a result, determinacy-based arguments in support of representationalism are not strong (...) ones. (shrink)
I propose a new argument showing that conscious vision sometimes depends constitutively on conscious attention. I criticise traditional arguments for this constitutive connection, on the basis that they fail adequately to dissociate evidence about visual consciousness from evidence about attention. On the same basis, I criticise Ned Block's recent counterargument that conscious vision is independent of one sort of attention (‘cognitive access'). Block appears to achieve the dissociation only because he underestimates the indeterminacy of visual consciousness. I then appeal to (...) empirical work on the interaction between visual indeterminacy and attention, to argue for the constitutive connection. (shrink)
How should we characterize the functional role of conscious visual experience? In particular, how do the conscious contents of visual experience guide, bear upon, or otherwise inform our ongoing motor activities? According to an intuitive and (I shall argue) philosophically influential conception, the links are often quite direct. The contents of conscious visual experience, according to this conception, are typically active in the control and guidance of our fine-tuned, real-time engagements with the surrounding three-dimensional world. But this idea (which I (...) shall call the Assumption of Experience-Based Control) is hostage to empirical fortune. It is a hostage, moreover, whose safety is in serious doubt. Thus Milner and Goodale (1995) argue for a deep and abiding dissociation between the contents of conscious seeing, on the one hand, and the resources used for the on-line guidance of visuo-motor action, on the other. This ‘dual visual systems’ hypothesis, which finds many echoes in various other bodies of cognitive scientific research, poses a prima facie challenge to the Assumption of Experience-Based Control. More importantly, it provides (I shall argue) fuel for an alternative and philosophically suggestive account of the functional role of conscious visual experience. (shrink)
I argue against a Disjunctive approach to visual experience. I then critique three 'common-factor' views: Qualia Theory, Intentionalism and Sense-Date Theory. The latter two are combined to form Intentional Trope Theory; and that view is defended.
John Campbell argues that visual attention to objects is the means by which we can refer to objects, and that this is so because conscious visual attention enables us to retrieve information about a location. It is argued here that while Campbell is right to think that we visually attend to objects, he does not give us sufficient ground for thinking that consciousness is involved, and is wrong to assign an intermediary role to location. Campbell’s view on sortals is also (...) queried, as is his espousal of the so-called Referential View of Experience. (shrink)
Visual thinking -- visual imagination or perception of diagrams and symbol arrays, and mental operations on them -- is omnipresent in mathematics. Is this visual thinking merely a psychological aid, facilitating grasp of what is gathered by other means? Or does it also have epistemological functions, as a means of discovery, understanding, and even proof? By examining the many kinds of visual representation in mathematics and the diverse ways in which they are used, Marcus Giaquinto argues that visual thinking in (...) mathematics is rarely just a superfluous aid; it usually has epistemological value, often as a means of discovery. Drawing from philosophical work on the nature of concepts and from empirical studies of visual perception, mental imagery, and numerical cognition, Giaquinto explores a major source of our grasp of mathematics, using examples from basic geometry, arithmetic, algebra, and real analysis. He shows how we can discern abstract general truths by means of specific images, how synthetic a priori knowledge is possible, and how visual means can help us grasp abstract structures. Visual Thinking in Mathematics reopens the investigation of earlier thinkers from Plato to Kant into the nature and epistemology of an individual's basic mathematical beliefs and abilities, in the new light shed by the maturing cognitive sciences. Clear and concise throughout, it will appeal to scholars and students of philosophy, mathematics, and psychology, as well as anyone with an interest in mathematical thinking. (shrink)
Recent work in "embodied, embedded" cognitive science links mental contents to large-scale distributed effects: dynamic patterns implicating elements of (what are traditionally seen as) sensing, reasoning and acting. Central to this approach is an idea of biological cognition as profoundly "action-oriented" - geared not to the creation of rich, passive inner models of the world, but to the cheap and efficient production of real-world action in real-world context. A case in point is Hurley's (1998) account of the profound role of (...) motor output in fixing the contents of conscious visual awareness - an account that also emphasizes distributed vehicles and long-range dynamical loops. Such stories can seem dramatically opposed to accounts, such as Milner and Goodale (1995), that stress relatively local mechanisms and that posit firm divisions between processes of visual awareness and of visuomotor action. But such accounts, I argue, can be deeply complimentary and together illustrate an important lesson. The lesson is that cognition may be embodied and action-oriented in two distinct - but complimentary - ways. There is a way of being embodied and action-oriented that implies being closely geared to the fine-grained control of low level effectors (hands, arms, legs and so on). And there is a way of being embodied and action-oriented that implies being closely geared to gross motor intentions, current goals, and schematic motor plans. Human cognition, I suggest, is embodied and action-oriented in both these ways. But the neural systems involved, and the size and scope of the key dynamic loops, may be quite different in each case. (shrink)