The Objective Threshold/Strategic Model proposes that strong, qualitative inferences of unconscious perception can be made if the relationship between perceptual sensitivity and stimulus visibility is nonlinear and nonmonotonic. The model proposes a nadir in priming effects at the objective identification threshold . These predictions were tested with masked semantic priming and repetition priming of a lexical decision task. The visibility of the prime stimuli was systematically varied above and below the objective identification threshold. The obtained relationship between prime visibility (...) and priming facilitation was nonlinear, but the results failed to confirm a nadir in priming effects at the objective identification threshold. We conclude that the objective identification threshold does not necessarily indicate the point where presumably unconscious priming effects might be inhibited by conscious cognitive processes. (shrink)

Perceptual learning involves an improvement in perceptual judgment with practice, which is often specific to stimulus or task factors. Perceptual learning has been shown on a range of visual tasks but very little research has explored chromatic perceptual learning. Here, we use two low level perceptual threshold tasks and a supra-threshold target detection task to assess chromatic perceptual learning and category effects. Experiment 1 investigates whether chromatic thresholds reduce as a result of training (...) and at what level of analysis learning effects occur. Experiment 2 explores the effect of category training on chromatic thresholds, whether training of this nature is category specific and whether it can induce categorical responding. Experiment 3 investigates the effect of category training on a higher level, lateralized target detection task, previously found to be sensitive to category effects. The findings indicate that performance on a perceptual threshold task improves following training but improvements do not transfer across retinal location or hue. Therefore, chromatic perceptual learning is category specific and can occur at relatively early stages of visual analysis. Additionally, category training does not induce category effects on a low level perceptual threshold task, as indicated by comparable discrimination thresholds at the newly learned hue boundary and adjacent test points. However, category training does induce category effects on a supra-threshold target detection task. Whilst chromatic perceptual learning is possible, learnt category effects appear to be a product of left hemisphere processing, and may require the input of higher level linguistic coding processes in order to manifest. (shrink)

Categorical perception (CP) is said to occur when a continuum of equally spaced physical changes is perceived as unequally spaced as a function of category membership (Harnad, S. (Ed.) (1987). Psychophysical and cognitive aspects of categorical perception: A critical overview. Cambridge: Cambridge University Press). A common suggestion is that CP for color arises because perception is qualitatively distorted when we learn to categorize a dimension. Contrary to this view, we here report that English speakers show no evidence of lowered discrimination (...) thresholds at the boundaries between blue and green categories even though CP is found at these boundaries in a supra-threshold task. Furthermore, there is no evidence of different discrimination thresholds between individuals from two language groups (English and Korean) who use different color terminology in the blue-green region and have different supra-threshold boundaries. Our participants' just noticeable difference (JND) thresholds suggest that they retain a smooth continuum of perceptual space that is not warped by stretching at category boundaries or by within-category compression. At least for the domain of color, categorical perception appears to be a categorical, but not a perceptual phenomenon. (shrink)

I assess the conditions that philosophers of mind usually use to identify mental representations. I argue in favor of a minimal definition of mental representation, which is similar to definitions endorsed by some philosophers of embodied cognition. I claim that, even if we endorse this minimal definition of mental representation, important aspects of perception cannot be explained in representational terms. Therefore I suggest endorsing a non-representational approach to perception made of a combination of the enactive approach and ecological psychology and (...) claim that perception is a direct relation to opportunities for action offered by perceptual niches. (shrink)

I argue that there are no irrational visual experiences, if we mean just the experiences that one is having now, but there are irrational visual experiences, if we mean also the experiences that one has had in the past. In other words, I will be arguing that perceptual irrationality is a retrospective phenomenon. So as to further support the first conjunct of my thesis, and to contextualize it among contemporary discussions, I also critique Susanna Siegel’s proposal that one could (...) be having an irrational experience, in the sense of a hijacked experience that has inherited a sub-threshold epistemic charge from a corrupt outlook. The present discussion is conducted from a Husserlian point of view, according to which perception is rational, rather than arational. I am, however, in this paper, not undertaking to defend the Husserlian view or the rationality of perception, or even to argue that the view I refer to as Husserlian is, in all aspects, the view that Edmund Husserl actually held. I aim merely to provide certain clarifications concerning the more specific topic of irrational visual experiences. (shrink)

The dominant view of the ventral and dorsal visual systems is that they subserve perception and action. De Wit, Van der Kamp, and Masters suggested that a more fundamental distinction might exist between the nature of information exploited by the systems. The present study distinguished between these accounts by asking participants to perform delayed matching , pointing and perceptual judgment responses to masked Müller–Lyer stimuli of varying length. Matching and pointing responses of participants who could not perceptually judge stimulus (...) length at brief durations remained sensitive to veridical stimulus length , but not the illusion , which was effective at long durations. Distinct thresholds for egocentric and allocentric information pick up were thus evident irrespective of whether perception or action responses were required. It was concluded that the dorsal and ventral systems may be delineated fundamentally by fast egocentric- and slower allocentric information pick up, respectively. (shrink)

Negative compatibility effects in the masked-prime paradigm are usually obtained when primes are masked effectively. With ineffective masks—and primes above the perceptual threshold—positive compatibility effects occur. We investigated whether this pattern reflects a causal relationship between conscious awareness and low-level motor control, or whether it reflects the fact that both are affected in the same way by changes in physical stimulus attributes. In a 5-session perceptual learning task, participants learned to consciously identify masked primes. However, they showed unaltered (...) NCEs that were not different from those produced by participants in a control group without equivalent perceptual learning. A control experiment demonstrated that no NCEs occur when prime identification is made possible by ineffective masking. The results suggest that perceptual awareness and low-level motor control are affected by the same factors, but are fundamentally independent of each other. (shrink)

This article reports four subliminal perception experiments using the relationship between confidence and accuracy to assess awareness. Subjects discriminated among stimuli and indicated their confidence in each discrimination response. Subjects were classified as being aware of the stimuli if their confidence judgments predicted accuracy and as being unaware if they did not. In the first experiment, confidence predicted accuracy even at stimulus durations so brief that subjects claimed to be performing at chance. This finding indicates that subjects's claims that they (...) are ''just guessing'' should not be accepted as sufficient evidence that they are completely unaware of the stimuli. Experiments 2-4 tested directly for subliminal perception by comparing the minimum exposure duration needed for better than chance discrimination performance against the minimum needed for confidence to predict accuracy. The latter durations were slightly but significantly longer, suggesting that under certain circumstances people can make perceptual discriminations even though the information that was used to make those discriminations is not consciously available. (shrink)

We have previously found that attention to internal somatic sensations during a heart beat perception task increases the misperception of external touch on a somatic signal detection task , during which healthy participants erroneously report feeling near-threshold vibrations presented to their fingertip in the absence of a stimulus. However, it has been suggested that mindful interoceptive attention should result in more accurate somatic perception, due to its non-evaluative and controlled nature. To investigate this possibility, 62 participants completed the SSDT before (...) and after a period of brief body-scan mindfulness meditation training, or a control intervention . The meditation intervention reduced tactile misperception and increased sensitivity during the SSDT. This finding suggests that the perceptual effects of interoceptive attention depend on its particular nature, and raises the possibility that body-scan meditation could reduce the misperception of physical symptoms in individuals with medically unexplained symptoms. (shrink)

Conscious access to fear-relevant information is mediated by threshold The present report proposed a model of access consciousness to fear-relevant information according to which there is a threshold for emotional perception beyond that the subject makes hits with no false alarm. The model was examined by having the participants performed a confidence-ratings masking task with fearful faces. Measures of the thresholds for conscious access were taken by looking at the receiver operating characteristics curves generated from a three-state low- and (...) high-threshold model by Krantz. Indeed, the analysis of the masking data revealed that the ROCs had threshold-like-nature rather continuous challenging in this fashion the classical signal-detection view on perceptual processing. Moreover, the threshold ROC curve exhibited the specific y-intercepts relevant to conscious access performance. The study suggests that the threshold can be an intrinsic property of conscious access, mediating emotional contents between perceptual states and consciousness. (shrink)

Experimentation is at the heart of scientific inquiry. In the behavioral and neural sciences, where only a limited number of observations can often be made, it is ideal to design an experiment that leads to the rapid accumulation of information about the phenomenon under study. Adaptive experimentation has the potential to accelerate scientific progress by maximizing inferential gain in such research settings. To date, most adaptive experiments have relied on myopic, one-step-ahead strategies in which the stimulus on each trial is (...) selected to maximize inference on the next trial only. A lingering question in the field has been how much additional benefit would be gained by optimizing beyond the next trial. A range of technical challenges has prevented this important question from being addressed adequately. This study applies dynamic programming, a technique applicable for such full-horizon, “global” optimization, to model-based perceptual threshold estimation, a domain that has been a major beneficiary of adaptive methods. The results provide insight into conditions that will benefit from optimizing beyond the next trial. Implications for the use of adaptive methods in cognitive science are discussed. (shrink)

In a recent article, [Sergent, C. & Dehaene, S. . Is consciousness a gradual phenomenon? Evidence for an all-or-none bifurcation during the attentional blink, Psychological Science, 15, 720–729] claim to give experimental support to the thesis that there is a clear transition between conscious and unconscious perception. This idea is opposed to theoretical arguments that we should think of conscious perception as a continuum of clarity, with e.g., fringe conscious states [Mangan, B. . Sensation’s ghost—the non-sensory “fringe” of consciousness, Psyche, (...) 7, 18]. In the experimental study described in this article, we find support for this opposite notion that we should have a parsimonious account of conscious perception. Our reported finding relates to the hypothesis that there is more than one perceptual threshold [Merikle, P.M., Smilek, D. & Eastwood, J.D. . Perception without awareness: perspectives from cognitive psychology, Cognition, 79, 115–134], but goes further to argue that there are different “levels” of conscious perception. (shrink)

Thomas Hardy’s great and central poem, “The Darkling Thrush,”1 signals that it is to be read as a response to his precursors. “Darkling” evokes Keats’s “Ode to a Nightingale” and Arnold’s “Dover Beach.” Byron had used “cloudy canopy” to describe Parnassus in Childe Harold’s Pilgrimage. A particularly ambitious signal is “coppice,” a variant of “copse,” a crucial word in Wordsworth’s “Tintern Abbey.”2 “Gate” fixes the coppice at the perceptual threshold, whereas Wordsworth located the copse at the center of the (...) landscape.Wordsworth situates the observer opposite, but in connection with, the natural setting. Beyond what is present to the senses lies a remote reality:On the near side, “here, under this dark .. (shrink)

Detection thresholds for a small light spot were measured at various distances from the colinear inucer edges of white inducing elements on a dark background. The data show that thresholds are elevated when the target is located close to one or more inducing element(s). Threshold elevations diminish with increasing distance of the target from colinear edges and decreasing surface size of the inducing elements. gradients show the same tendencies. Tbe present observations add empirical support to the idea that (...) illusory figures are determined by local mechanisms that operate at early stages of perceptual information processing and decision. (shrink)

Dogmatists and phenomenal conservatives think that if it perceptually seems to you that p, then you thereby have some prima facie justification for believing that p. Increasingly, writers about these views have argued that perceptual seemings are composed of two other states: a sensation followed by a seeming. In this article we critically examine this movement. First we argue that there are no compelling reasons to think of perceptual seemings as so composed. Second we argue that even if (...) they were so composed, this underlying disunity in metaphysical or psychological structure would fall below the threshold of epistemic significance. (shrink)

Perceptual conscious experiences result from non-conscious processes that precede them. We document a new characteristic of the cognitive system: the speed with which visual meaningful stimuli are prioritized to consciousness over competing noise in visual masking paradigms. In ten experiments (N = 399) we find that an individual's non-conscious visual prioritization speed (NVPS) is ubiquitous across a wide variety of stimuli, and generalizes across visual masks, suppression tasks, and time. We also find that variation in NVPS is unique, in (...) that it cannot be explained by variation in general speed, perceptual decision thresholds, short-term visual memory, or three networks of attention (alerting, orienting and executive). Finally, we find that NVPS is correlated with subjective measures of sensitivity, as they are measured by the Highly Sensitive Person scale. We conclude by discussing the implications of variance in NVPS for understanding individual variance in behavior and the neural substrates of consciousness. (shrink)

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, edge-like inducers defined by luminance contrast to spatial facilitation with targets and inducers (...) defined by color contrast. The results of a first experiment show that achromatic inducers facilitate the detection of achromatic targets on gray and colored backgrounds, but tend to suppress the detection of chromatic targets. Chromatic inducers facilitate the detection of chromatic targets on gray and colored backgrounds, but tend to suppress the detection of achromatic targets. Chromatic spatial facilitation appears to be strongest when inducers and background are isoluminant. The results of a second experiment show that spatial facilitation with chromatic targets and inducers requires a longer exposure duration of the inducers than spatial facilitation with achromatic targets and inducers, which is already fully effective at an inducer exposure of 30 ms only. The findings point towards two separate mechanisms for spatial facilitation with collinear form stimuli: one that operates in the domain of luminance, and one that operates in the domain of color contrast. These results are consistent with neural models of boundary and surface formation which suggest that achromatic and chromatic visual cues are represented on different cortical surface representations that are capable of selectively attracting attention. Multiple copies of these achromatic and chromatic surface representations exist corresponding to different ranges of perceived depth from an observer, and each can attract attention to itself. Color and contrast differences between inducing and test stimuli, and transient responses to inducing stimuli, can cause attention to shift across these surface representations in ways that sometimes enhance and sometimes interfere with target detection. (shrink)

Light increment thresholds were measured on either side of one of the illusory contours of a white-on-black Kanizsa square and on the illusory contour itself. The data show that thresholds are elevated when measured on either side of the illusory border. These elevations diminish with increasing distance of the target spot from the white elements which induce the illusory figure. The most striking result, however, is that threshold elevations are considerably lower or even absent when the target is (...) located on the illusory contour itself. At an equivalent position in a control figure where no illusory contour is visible, such a threshold decrease does not occur. The present observations add empirical support to neural theories of illusory form perception. (shrink)

Inattentional blindness is described as the failure to perceive a supra-threshold stimulus when attention is directed away from that stimulus. Based on performance on an explicit recognition memory test and concurrent functional imaging data Rees, Russell, Frith, and Driver [Rees, G., Russell, C., Frith, C. D., & Driver, J. . Inattentional blindness versus inattentional amnesia for fixated but ignored words. Science, 286, 2504–2507] reported inattentional blindness for word stimuli that were fixated but ignored. The present study examined both explicit and (...) implicit memory for fixated but ignored words using a selective-attention task in which overlapping picture/word stimuli were presented at fixation. No explicit awareness of the unattended words was apparent on a recognition memory test. Analysis of an implicit memory task, however, indicated that unattended words were perceived at a perceptual level. Thus, the selective-attention task did not result in perfect filtering as suggested by Rees et al. While there was no evidence of conscious perception, subjects were not blind to the implicit perceptual properties of fixated but ignored words. (shrink)

Wagering contingent on a previous decision, or post-decision wagering, has recently been proposed to measure conscious awareness. Whilst intuitively appealing, it remains unclear whether economic context interacts with subjective confidence and how such interactions might impact on the measurement of awareness. Here we propose a signal detection model which predicts that advantageous wagers placed on the identity of preceding stimuli are affected by loss aversion, despite stimulus visibility remaining constant. This pattern of predicted results was evident in a psychophysical task (...) where we independently manipulated perceptual and economic factors. Changes in wagering behaviour induced by changes in wager size were largely driven by changes in criterion, consistent with the model. However, for near-threshold stimuli, a reduction in wagering efficiency was also evident, consistent with an apparent but potentially illusory decrease in awareness of the stimulus. These findings challenge an assertion that post-decision wagering provides a direct index of subjective awareness. (shrink)

We assessed how synchronous speech listening and lipreading affects speech recognition in acoustic noise. In simple audiovisual perceptual tasks, inverse effectiveness is often observed, which holds that the weaker the unimodal stimuli, or the poorer their signal-to-noise ratio, the stronger the audiovisual benefit. So far, however, inverse effectiveness has not been demonstrated for complex audiovisual speech stimuli. Here we assess whether this multisensory integration effect can also be observed for the recognizability of spoken words. To that end, we presented (...) audiovisual sentences to 18 native-Dutch normal-hearing participants, who had to identify the spoken words from a finite list. Speech-recognition performance was determined for auditory-only, visual-only (lipreading) and auditory-visual conditions. To modulate acoustic task difficulty, we systematically varied the auditory signal-to-noise ratio. In line with a commonly-observed multisensory enhancement on speech recognition, audiovisual words were more easily recognized than auditory-only words (recognition thresholds of -15 dB and -12 dB, respectively). We here show that the difficulty of recognizing a particular word, either acoustically or visually, determines the occurrence of inverse effectiveness in audiovisual word integration. Thus, words that are better heard or recognized through lipreading, benefit less from bimodal presentation. Audiovisual performance at the lowest acoustic signal-to-noise ratios (45%) fell below the visual recognition rates (60%), reflecting an actual deterioration of lipreading in the presence of excessive acoustic noise. This suggests that the brain may adopt a strategy in which attention has to be divided between listening and lipreading. (shrink)

Diffusion models are widely-used and successful accounts of the time course of two-choice decision making. Most diffusion models assume constant boundaries, which are the threshold levels of evidence that must be sampled from a stimulus to reach a decision. We summarize theoretical results from statistics that relate distributions of decisions and response times to diffusion models with time-varying boundaries. We then develop a computational method for finding time-varying boundaries from empirical data, and apply our new method to two problems. The (...) first problem involves finding the time-varying boundaries that make diffusion models equivalent to the alternative sequential sampling class of accumulator models. The second problem involves finding the time-varying boundaries, at the individual level, that best fit empirical data for perceptual stimuli that provide equal evidence for both decision alternatives. We discuss the theoretical and modeling implications of using time-varying boundaries in diffusion models, as well as the limitations and potential of our approach to their inference. (shrink)

In order to identify the neural correlates of consciousness it is necessary to distinguish these from the neural correlates associated with unconscious information processing. We describe the various techniques, such as masking, which can be used to generate conditions in which the same stimulus is presented either just above or just below a threshold for visibility. Directed attention can also be used to manipulate the extent to which a stimulus gains access to awareness, as can various methods for creating bi‐stable (...) perception. A major problem for these studies is the possible confound of the need for participants to report their awareness and there is currently much interest in developing paradigms in which reporting awareness is not required. We also discuss studies exploring the neural correlates of imagination, illusions and hallucinations in which a perceptual experience occurs in the absence of a physical stimulus. Finally we consider techniques that go beyond correlation and attempt to identify the necessary and sufficient neural processes leading to conscious experience. (shrink)

Monitoring the environment for visual events while performing a concurrent task requires adjustment of visual processing priorities. By use of Bundesen's (1990) Theory of Visual Attention (TVA), we investigated how monitoring for an object-based brief event affected distinct components of visual attention in a concurrent task. The perceptual salience of the event was varied. Monitoring reduced the processing speed in the concurrent task, and the reduction was stronger when the event was less salient. The monitoring task neither affected the (...) temporal threshold of conscious perception nor the storage capacity of visual short-term memory nor the efficiency of top-down controlled attentional selection. (shrink)

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 detectors, and Grossberg's Adaptive Resonance Theory. A time-bin resonance model (...) is developed, where temporal signatures of conscious states are generated on the basis of signal reverberation across large distances in highly plastic neural circuits. The temporal signatures are delivered by neural activity patterns which, beyond a certain statistical threshold, activate, maintain, and terminate a conscious brain state like a bar code would activate, maintain, or inactivate the electronic locks of a safe. Such temporal resonance would reflect a higher level of neural processing, independent from sensorial or perceptual brain mechanisms. (shrink)

The neuroanatomical substrates controlling and regulating sleeping and waking, and thus consciousness, are located in the brain stem. Most crucial for bringing the brain into a state conducive for consciousness and information processing is the mesencephalic part of the brain stem. This part controls the state of waking, which is generally associated with a high degree of consciousness. Wakefulness is accompanied by a low-amplitude, high-frequency electroencephalogram, due to the fact that thalamocortical neurons fire in a state of tonic depolarization. Information (...) can easily pass the low-level threshold of these neurons, leading to a high transfer ratio. The complexity of the electroencephalogram during conscious waking is high, as expressed in a high correlation dimension. Accordingly, the level of information processing is high. Spindles, and alpha waves in humans, mark the transition from wakefulness to sleep. These phenomena are related to drowsiness, associated with a reduction in consciousness. Drowsiness occurs when cells undergo moderate hyperpolarizations. Increased inhibitions result in a reduction of afferent information, with a lowered transfer ratio. Information processing subsides, which is also expressed in a diminished correlation dimension. Consciousness is further decreased at the onset of slow wave sleep. This sleep is controlled by the medullar reticular formation and is characterized by a high-voltage, low-frequency electroencephalogram. Slow wave sleep becomes manifest when neurons undergo a further hyperpolarization. Inhibitory activities are so strong that the transfer ratio further drops, as does the correlation dimension. Thus, sensory information is largely blocked and information processing is on a low level. Finally, rapid eye movement sleep is regulated by the pontine reticular formation and is associated with a ''wake-like'' electroencephalographic pattern. Just as during wakefulness, this is the expression of a depolarization of thalamocortical neurons. The transfer ratio of rapid eye movement sleep has not yet been determined, but seems to vary. Evidence exists that this type of sleep, associated with dreaming, with some kind of perception and consciousness, is involved in processing of ''internal'' information. In line with this, rapid eye movement sleep has higher correlation dimensions than slow-wave sleep and sometimes even higher than wakefulness. It is assumed that the ''near-the-threshold'' depolarized state of neurons in the thalamus and cerebral cortex is a necessary condition for perceptual processes and consciousness, such as occurs during waking and in an altered form during rapid eye movement sleep. (shrink)

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 detectors, and Grossberg’s Adaptive Resonance Theory. A time-bin resonance model (...) is developed, where temporal signatures of conscious states are generated on the basis of signal reverberation across large distances in highly plastic neural circuits. The temporal signatures are delivered by neural activity patterns which, beyond a certain statistical threshold, activate, maintain, and terminate a conscious brain state like a bar code would activate, maintain, or inactivate the electronic locks of a safe. Such temporal resonance would reflect a higher level of neural processing, one that is independent from sensorial or perceptual brain mechanisms. (shrink)

If it is true, as one of its founders, George Miller, tells us, that cognitive science was born in 1956, then by human aging standards it is coming upon a mid-life crisis. Crises, as Kuhn has taught us, often precipitate radical change, in science as well as in individuals. It should therefore not be surprising to find that cognitive scientists have begun to look to the future and predict, or hope, that it will include both the beautiful and the good. (...) Thus it is that the neuroscientist, Semir Zeki, has recently declared: “We are at the threshold of a great enterprise” which he calls neuroesthetics. His optimism about that enterprise has been echoed by a number of other researchers; and for the most part, their hopefulness is based on discoveries about how pictures are perceived. So, for example, V. S. Ramachandran and William Hirstein have said that by understanding the neuropsychological principles of picture perception, we may come to understand the very “essence of art”. Indeed, by identifying perceptual principles in the right way, according to David Gilden, we may discover common ground for normative disciplines of all stripes; a theory of “what is sexy, what is virtue, or what is a good buy”. (shrink)

We addressed the questions whether stimuli presented below the threshold of verbal awareness are nevertheless perceived and whether there are perceptual differences between the two cerebral hemispheres. Pictures of line drawn objects and animals were subliminally presented to each visual half-field for subsequent identification in a form as fragmented as possible. The performance of 40 healthy subjects was compared to that of 63 controls. Whereas identification performance after blank presentation in the experimental group did not differ from that of (...) controls, identification in a significantly more fragmented form was achieved after the presentation of the complete picture. This effect, however, occurred only after subliminal stimulation in the left visual field, i.e., of the right hemisphere. Our results show that pictures presented below the threshold of verbal awareness can be perceived, and that only the right hemisphere can perceive them and make use of the perception. It remains an open question whether this kind of hemispheric specialization represents a right hemisphere dominance for subliminal perception or reflects an inability of the left hemisphere to access and behaviorally use unaware percepts via fragmented picture identification, for which a right hemisphere advantage is known. (shrink)

Human vision supports prediction for moving stimuli. Here we take an individual differences approach to investigate whether there could be a common processing rate for motion-based visual prediction across diverse motion phenomena. Motion Induced Spatial Conflict refers to an incongruity arising from two edges of a combined stimulus, moving rigidly, but with different apparent speeds. This discrepancy induces an illusory jitter that has been attributed to conflict within a motion prediction mechanism. Its apparent frequency has been shown to correlate with (...) the frequency of alpha oscillations in the brain. We asked what other psychophysical measures might correlate positively with MISC frequency. We measured the correlation between MISC jitter frequency and another three measures that might be linked to motion-based spatial prediction. We demonstrate that the illusory jitter frequency in MISC correlates significantly with the accrual rate of the Motion Induced Position Shift effect - the well-established observation that a carrier movement in a static envelope of a Gabor target leads to an apparent position shift of the envelope in the direction of motion. We did not observe significant correlations with the other two measures – the Adaptation Induced Spatial Shift accrual rate and the Smooth Motion Threshold. These results suggest a shared perceptual rate between MISC and MIPS, implying a common periodic mechanism for motion-based visual prediction. (shrink)

If it is true, as one of its founders, George Miller, tells us, that cognitive science was born in 1956, then by human aging standards it is coming upon a mid-life crisis. Crises, as Kuhn has taught us, often precipitate radical change, in science as well as in individuals. It should therefore not be surprising to find that cognitive scientists have begun to look to the future and predict, or hope, that it will include both the beautiful and the good. (...) Thus it is that the neuroscientist, Semir Zeki, has recently declared: “We are at the threshold of a great enterprise” which he calls neuroesthetics. His optimism about that enterprise has been echoed by a number of other researchers; and for the most part, their hopefulness is based on discoveries about how pictures are perceived. So, for example, V. S. Ramachandran and William Hirstein have said that by understanding the neuropsychological principles of picture perception, we may come to understand the very “essence of art”. Indeed, by identifying perceptual principles in the right way, according to David Gilden, we may discover common ground for normative disciplines of all stripes; a theory of “what is sexy, what is virtue, or what is a good buy”. (shrink)

Piéron's Law describes the relationship between stimulus intensity and reaction time. Previously (Stafford & Gurney, 2004), we have shown that Piéron's Law is a necessary consequence of rise-to-threshold decision making and thus will arise from optimal simple decision-making algorithms (e.g., Bogacz, Brown, Moehlis, Holmes, & Cohen, 2006). Here, we manipulate the color saturation of a Stroop stimulus. Our results show that Piéron's Law holds for color intensity and color-naming reaction time, extending the domain of this law, in line with our (...) suggestion of the generality of the processes that can give rise to Piéron's Law. In addition, we find that Stroop condition does not interact with the effect of color saturation; Stroop interference and facilitation remain constant at all levels of color saturation. An analysis demonstrates that this result cannot be accounted for by single-stage decision-making algorithms which combine all the evidence pertaining to a decision into a common metric. This shows that human decision making is not information-optimal and suggests that the generalization of current models of simple perceptual decision making to more complex decisions is not straightforward. (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 lieu of an abstract, here is a brief excerpt of the content:John Robert Leo CRITICISM OF CONSCIOUSNESS IN SHELLEY'S A DEFENCE OF POETRY IN his "Ode to Liberty" Shelley locates by encircling and enfolding metaphors a mythic Hellenic moment, one in which verse was yet "speechless" and philosophy still burdened with "lidless eyes." Greece— always for Shelley either the displaced Garden of prethematic unity or the mythic dream of integrated civic and aesthetic life—is about to inaugurate Athens and the (...) "wrinkled image" of historical consciousness.1 Poetry, thinking, and the tilling of an earth "to human use" are implicitly related and foreseen as destiny: from their enchanted caves Prophetic echoes flung dim melody. On the unapprehensive wild The vine, the corn, the olive mild, Grew savage yet, to human use unreconciled; And, like unfolded flowers beneath the sea, Like the man's dark thought in the infant's brain, Like aught that is which wraps what is to be, Art's deathless dreams lay veiled by many a vein Of Parian stone; and, yet a speechless child, Verse murmured, and Philosophy did strain Her lidless eyes for thee... (11. 49-60). Shelley could be describing the reading or speaking of a text, for poetic experience is an originating moment which unfolds our reflections and anticipations. Poetry elides speechlessness and the empty gaze. Its goings are all returnings, its experience is always inventive before meanings codify and resolve: "Every original language near to its source," we find in the Defence (p. 279), "is in itself the chaos of a cyclic poem; the copiousness of lexicography and the distinctions of grammar are the works of a later age and are merely the catalogue and the form of the creations of poetry." What was dark to experience is now illumined, 46 John Robert Leo47 as different regions in experience are uncovered or redistributed by language across our shifting horizons. Thus this bringing-foward-intoclarity, this moving of the previously inexpressed into articulation, is the pattern not only behind Shelley's view ofGreece producing a "sun-fire garlanded" Athens (1. 68), but also the more pervasive design describing other regarded experience. James Edie puts it this way: "We... can learn to make distinctions in our experience by attending to differences of meaning which are normally below the level of our own cultural threshold. By attending to a given region of experience, we can lower the differential thresholds already sedimented in our language almost indefinitely and make what was implicit in our experience more and more explicit."2 Edie's comments may be taken as responses to questions emerging from modernist readings of Shelley and other visionary poets—Blake, Hart Crane, or Charles Olson are instances—who sense the poetic project as a criticism of consciousness, within the lived body, as it struggles to make a world. How do language and the imagination consort in the critical regeneration of our lives? In what sorts of ways is renascence the uncovering and unfolding of an indefinite wholeness by the unlayering of fixed habits and attitudes? How does Shelley's Defence of Poetry, both a text on aesthetics and a reading of the world, suggest their alignment? What methods from critical discourse make Shelley's poetics present to our experience and thought? The adjustment of these issues is the task of the remainder of my article. First I examine Shelley's organization of consciousness into "reason" and "imagination" and trace the meanings of these functions in their immediate social context. A brief dispute with the reductive idealism of Platonic tradition allows for my third procedure, which is a phenomenological description of the imaginative field according to Husserl. Finally, I try to explicate Shelley's understanding of imaginative "decentering" within our experience. I Poetry and prose are saturated with references to phenomena. Texts refer to interior and exterior events (memory, rain), which are objects ofandfor consciousness. Shelley grasps this co-givenness of consciousness and world, their correlativity, as a condition revealed and strengthened by metaphor, which itself arrests us as "that of which we are speaking through words."3 But if it is the nature of language to be both perceptual and yet transcendental, both present and absent, it still exists as the imagination's voice in... (shrink)

Recently, the thesis that experience is fundamentally a matter of representing the world as being a certain way has been questioned by austere relationalists. I defend this thesis by developing a view of perceptual content that avoids their objections. I will argue that on a relational understanding of perceptual content, the fundamental insights of austere relationalism do not compete with perceptual experience being representational. As it will show that most objections to the thesis that experience has content (...) apply only to accounts of perceptual content on which perceptual relations to the world play no explanatory role. With austere relationalists, I will argue that perceptual experience is fundamentally relational. But against austere relationalists, I will argue that it is fundamentally both relational and representational. (shrink)

The Threshold of the Visible World advances a revolutionary new political aesthetic--Kaja Silverman explores the possibilities for looking beyond the restrictive mandates of the self, and the normative aspects of the cultural image-repertoire. She provides a detailed account of the social and psychic forces which constrain us to look and identify in normative ways, and the violence which that normativity implies. Accounting for these phenomena on both a conscious and an unconcious level, Silverman analyzes the psychic and textual conditions under (...) which our "field of vision" can be expanded. The title of this book is taken from Lacan's essay on the mirror stage. In that text, Lacan writes that "the mirror-image would seem to be the threshold of the visible world." He thereby suggests that the visible world has no existence as such until the infant subject has access to an image of self. Lacan intimates that the mirror provides the frame through which one relates to others within the domain of vision, stressing the priority of narcissism and the ego over all other libidinal transactions. The Threshold of the Visible World provides a psychic, social and political specification of Lacan's claim, and most particularly of its implications for the subject's relations to the social other. This is accomplished through examination of the ego, as well as two other categories at the center of Lacan's account of the mirror stage: ideality and identification. This book is an ethical-political project which leads to the re-elaboration of a number of crucial theoretical categories--Silverman offers an account of the bodily ego, of identification, of idealization, of the gaze, of the look, and of the "photographic." The Threshold of the Visible World leads as well to the formulation of a fresh model for conceptualizing sexual, racial and class "difference," and the terms under which it might be dismantled. This book thus seeks to apprehend the field of vision through the frame of a different kind of bodily ego, and discover the pleasures to be derived from corporeal transport. (shrink)

Both common sense and dominant traditions in art criticism and philosophical aesthetics have it that aesthetic features or properties are perceived. However, there is a cast of reasons to be sceptical of the thesis. This paper defends the thesis—that aesthetic properties are sometimes represented in perceptual experience—against one of those sceptical opponents. That opponent maintains that perception represents only low-level properties, and since all theorists agree that aesthetic properties are not low-level properties, perception does not represent aesthetic properties. I (...) offer a novel argument—what I call the argument from seeing-as—against that sceptic which moves from consideration of ambiguous figures to consideration of visual art. It concludes that aesthetic properties are sometimes perceived and delivers a general lesson for philosophy of perception. Contrary to extant theories of rich perceptual content, aesthetic properties are far better candidates for high-level perceptual contents than standardly theorized rich contents like natural kinds. (shrink)

Perceptual experiences are not immediately responsive to reasons. You see a stick submerged in a glass of water as bent no matter how much you know about light refraction. Due to this isolation from reasons, perception is traditionally considered outside the scope of epistemic evaluability as justified or unjustified. Is perception really as independent from reasons as visual illusions make it out to be? I argue no, drawing on psychological evidence from perceptual learning. The flexibility of perceptual (...) learning is a way of responding to new epistemic reasons. The resulting perceptual experiences are epistemically evaluable as justified or unjustified. (shrink)

I argue that perceptual consciousness is constituted by a mental activity. The mental activity in question is the activity of employing perceptual capacities, such as discriminatory, selective capacities. This is a radical view, but I hope to make it plausible. In arguing for this mental activist view, I reject orthodox views on which perceptual consciousness is analyzed in terms of peculiar entities, such as, phenomenal properties, external mind-independent properties, propositions, sense-data, qualia, or intentional objects.