Visual Systems Hypothesis Research Articles

The development of visual cognition: The emergence of spatial congruency bias

AbstractIn adults, spatial location plays a special role in visual object processing. People are more likely to judge two sequentially presented objects as being identical when they appear in the same location compared to in different locations (a phenomenon referred to as Spatial Congruency Bias [SCB]). However, no comparable Identity Congruency Bias (ICB) is found, suggesting an asymmetric location‐identity relationship in object binding. What gives rise to this asymmetric congruency bias? This paper considered two possible hypotheses. Hypothesis 1 suggests that the asymmetric congruency bias results from an inherently special role of location in the visual system. In contrast, Hypothesis 2 suggests that the asymmetric congruency bias is a product of development, reflecting people's experience with the world. To distinguish the two hypotheses, we tested both adults’ and 5‐year‐old children's SCB and ICB by Identity Judgment Experiments and Spatial Judgment Experiments, respectively. The study found that adults only exhibited a SCB, but no ICB. However, young children exhibited both SCB and ICB, suggesting a symmetric congruency bias and reciprocal influences between location and identity in early development. The results indicate that the asymmetric location‐identity relationship develops as object identity's influence on location gets pruned away, while location's influence on identity is preserved, possibly due to people's gained experiences with regularities of the world.Research Highlights Adults exhibit Spatial Congruency Bias—an asymmetric location‐identity relationship with location biasing their judgment of object identities, but not vice versa. Asymmetric congruency bias may result from an inherently special role of location in visual system (Hypothesis 1) or accumulated experiences with the world (Hypothesis 2). To distinguish the two hypotheses, the study investigated the Spatial Congruency Bias and Identity Congruency Bias in both adults and 5‐year‐old children. Unlike adults who exhibited only Spatial Congruency Bias, 5‐year‐old children exhibited both Spatial Congruency Bias and Identity Congruency Bias.

Investigating masked priming along the "vision-for-perception" and "vision-for-action" dimensions of unconscious processing.

The study of nonconscious priming is rooted in a long research tradition in experimental psychology and plays an important role for a range of topics, including visual recognition, emotion, decision making, and memory. Prime stimuli can be transiently suppressed from awareness by using a variety of psychophysical paradigms. The aim is to understand which stimulus features can be processed nonconsciously and influence behavior toward subsequently presented probe stimuli. Here, we tested the notion that continuous flash suppression (CFS), a relatively new method of interocular suppression, selectively disrupts stimulus identification mediated by the ventral "vision-for-perception" pathway, while preserving action-relevant stimulus features processed by the dorsal "vision-for-action" pathway. Given the far-reaching implications of this notion for the influential two visual systems hypothesis, and visual cognition in general, we investigated its empirical basis in a series of seven masked priming experiments using CFS. We did not find evidence for nonconscious priming of object categorization by action-relevant features. Based on these results, we recommend skepticism about the notion that the processing of action-relevant features under CFS is selectively preserved in the "vision-for-action" pathway. Second, we conclude that CFS experiments are less informative than approaches using visible stimuli, when the aim is to gather data in relation to the two visual systems hypothesis. Third, we propose that future nonconscious priming studies should carefully consider the position of suppression paradigms within a functional hierarchy of unconscious processing, thus constraining hypothesis generation to effects that are plausible given the employed methodology. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

The two visual systems hypothesis and contrastive underdetermination

This paper concerns local yet systematic problems of contrastive underdetermination of model choice in cognitive neuroscience debates about the so-called two visual systems hypothesis. The underdetermination problem is systematically generated by the way certain assumptions about the representationalist nature of computation are translated into experimental practice. The problem is that behavioural data underdetermine the choice between competing representational models. In this paper, I diagnose how these assumptions generate underdetermination problems in the choice between competing functional models of perception–action. Using the tools of philosophy of science, I describe the type of underdetermination and sketch a possible cure.

The Sander parallelogram illusion dissociates action and perception despite control for the litany of past confounds

The two visual systems hypothesis proposes that human vision is supported by an occipito-temporal network for the conscious visual perception of the world and a fronto-parietal network for visually-guided, object-directed actions. Two specific claims about the fronto-parietal network's role in sensorimotor control have generated much data and controversy: (1) the network relies primarily on the absolute metrics of target objects, which it rapidly transforms into effector-specific frames of reference to guide the fingers, hands, and limbs, and (2) the network is largely unaffected by scene-based information extracted by the occipito-temporal network for those same targets. These two claims lead to the counter-intuitive prediction that in-flight anticipatory configuration of the fingers during object-directed grasping will resist the influence of pictorial illusions. The research confirming this prediction has been criticized for confounding the difference between grasping and explicit estimates of object size with differences in attention, sensory feedback, obstacle avoidance, metric sensitivity, and priming. Here, we address and eliminate each of these confounds. We asked participants to reach out and pick up 3D target bars resting on a picture of the Sander Parallelogram illusion and to make explicit estimates of the length of those bars. Participants performed their grasps without visual feedback, and were permitted to grasp the targets after making their size-estimates to afford them an opportunity to reduce illusory error with haptic feedback. The results show unequivocally that the effect of the illusion is stronger on perceptual judgments than on grasping. Our findings from the normally-sighted population provide strong support for the proposal that human vision is comprised of functionally and anatomically dissociable systems.

Still holding after all these years: An action-perception dissociation in patient DF

Patient DF, who has bilateral damage in the ventral visual stream, is perhaps the best known individual with visual form agnosia in the world, and has been the focus of scores of research papers over the past twenty-five years. The remarkable dissociation she exhibits between a profound deficit in perceptual report and a preserved ability to generate relatively normal visuomotor behaviour was early on a cornerstone in Goodale and Milner's (1992) two visual systems hypothesis. In recent years, however, there has been a greater emphasis on the damage that is evident in the posterior regions of her parietal cortex in both hemispheres. Deficits in several aspects of visuomotor control in the visual periphery have been demonstrated, leading some researchers to conclude that the double dissociation between vision-for-perception and vision-for-action in DF and patients with classic optic ataxia can no longer be assumed to be strong evidence for the division of labour between the dorsal and ventral streams of visual processing. In this short review, we argue that this is not the case. Indeed, after evaluating DF's performance and the location of her brain lesions, a clear picture of a double dissociation between DF and patients with optic ataxia is revealed. More than quarter of a century after the initial presentation of DF's unique case, she continues to provide compelling evidence for the idea that the ventral stream is critical for the perception of the shape and orientation of objects but not the visual control of skilled actions directed at those objects.

The Perception‐Action Model: Counting Computational Mechanisms

AbstractMilner and Goodale's Two Visual Systems Hypothesis (TVSH) is regarded as common ground in recent discussions of visual consciousness. A central part of TVSH is a functional model of vision and action (a functional perception‐action model, PAM for short). In this paper, I provide a brief overview of these current discussions and argue that there is ambiguity between a strong and a weak version of PAM. I argue that, given a standard way of individuating computational mechanisms, the available evidence cannot be used to distinguish between these versions. This not only has consequences for philosophical theories of the role of visual consciousness but also for the role of experimental evidence in model testing in cognitive neuroscience.

The Effects of Optical Illusions in Perception and Action in Peripersonal and Extrapersonal Space

While the two visual system hypothesis tells a fairly compelling story about perception and action in peripersonal space (i.e., within arm's reach), its validity for extrapersonal space is very limited and highly controversial. Hence, the present purpose was to assess whether perception and action differences in peripersonal space hold in extrapersonal space and are modulated by the same factors. To this end, the effects of an optic illusion in perception and action in both peripersonal and extrapersonal space were compared in three groups that threw balls toward a target at a distance under different target eccentricity (i.e., with the target fixated and in peripheral field), viewing (i.e., binocular and monocular viewing), and delay conditions (i.e., immediate and delayed action). The illusory bias was smaller in action than in perception in peripersonal space, but this difference was significantly reduced in extrapersonal space, primarily because of a weakening bias in perception. No systematic modulation of target eccentricity, viewing, and delay arose. The findings suggest that the two visual system hypothesis is also valid for extra personal space.

Interactions between dorsal and ventral streams for controlling skilled grasp

The two visual systems hypothesis suggests processing of visual information into two distinct routes in the brain: a dorsal stream for the control of actions and a ventral stream for the identification of objects. Recently, increasing evidence has shown that the dorsal and ventral streams are not strictly independent, but do interact with each other. In this paper, we argue that the interactions between dorsal and ventral streams are important for controlling complex object-oriented hand movements, especially skilled grasp. Anatomical studies have reported the existence of direct connections between dorsal and ventral stream areas. These physiological interconnections appear to be gradually more active as the precision demands of the grasp become higher. It is hypothesised that the dorsal stream needs to retrieve detailed information about object identity, stored in ventral stream areas, when the object properties require complex fine-tuning of the grasp. In turn, the ventral stream might receive up to date grasp-related information from dorsal stream areas to refine the object internal representation. Future research will provide direct evidence for which specific areas of the two streams interact, the timing of their interactions and in which behavioural context they occur.

Conscious Vision in Action.

It is natural to assume that the fine-grained and highly accurate spatial information present in visual experience is often used to guide our bodily actions. Yet this assumption has been challenged by proponents of the Two Visual Systems Hypothesis (TVSH), according to which visuomotor programming is the responsibility of a "zombie" processing stream whose sources of bottom-up spatial information are entirely non-conscious (Clark, 2007, 2009; Goodale & Milner, 1992, 2004a; Milner & Goodale, 1995/2006, 2008). In many formulations of TVSH, the role of conscious vision in action is limited to "recognizing objects, selecting targets for action, and determining what kinds of action, broadly speaking, to perform" (Clark, 2007, p. 570). Our aim in this study is to show that the available evidence not only fails to support this dichotomous view but actually reveals a significant role for conscious vision in motor programming, especially for actions that require deliberate attention.

The Two Visual Systems Hypothesis: New Challenges and Insights from Visual form Agnosic Patient DF.

Patient DF, who developed visual form agnosia following carbon monoxide poisoning, is still able to use vision to adjust the configuration of her grasping hand to the geometry of a goal object. This striking dissociation between perception and action in DF provided a key piece of evidence for the formulation of Goodale and Milner’s Two Visual Systems Hypothesis (TVSH). According to the TVSH, the ventral stream plays a critical role in constructing our visual percepts, whereas the dorsal stream mediates the visual control of action, such as visually guided grasping. In this review, we discuss recent studies of DF that provide new insights into the functional organization of the dorsal and ventral streams. We confirm recent evidence that DF has dorsal as well as ventral brain damage – and that her dorsal-stream lesions and surrounding atrophy have increased in size since her first published brain scan. We argue that the damage to DF’s dorsal stream explains her deficits in directing actions at targets in the periphery. We then focus on DF’s ability to accurately adjust her in-flight hand aperture to changes in the width of goal objects (grip scaling) whose dimensions she cannot explicitly report. An examination of several studies of DF’s grip scaling under natural conditions reveals a modest though significant deficit. Importantly, however, she continues to show a robust dissociation between form vision for perception and form vision-for-action. We also review recent studies that explore the role of online visual feedback and terminal haptic feedback in the programming and control of her grasping. These studies make it clear that DF is no more reliant on visual or haptic feedback than are neurologically intact individuals. In short, we argue that her ability to grasp objects depends on visual feedforward processing carried out by visuomotor networks in her dorsal stream that function in the much the same way as they do in neurologically intact individuals.

A psychofunctionalist argument against nonconceptualism

In this paper I present a psychofunctionalist argument for conceptualism, the thesis that conscious visual experience is a conceptual state rather than a nonconceptual state. The argument draws on the holistic character of functionalist accounts of mind, together with the “Two Visual Systems Hypothesis” notably defended by Melvyn Goodale and David Milner.

Optic Ataxia: From Balint’s Syndrome to the Parietal Reach Region

Optic ataxia is a high-order deficit in reaching to visual goals that occurs with posterior parietal cortex (PPC) lesions. It is a component of Balint's syndrome that also includes attentional and gaze disorders. Aspects of optic ataxia are misreaching in the contralesional visual field, difficulty preshaping the hand for grasping, and an inability to correct reaches online. Recent research in nonhuman primates (NHPs) suggests that many aspects of Balint's syndrome and optic ataxia are a result of damage to specific functional modules for reaching, saccades, grasp, attention, and state estimation. The deficits from large lesions in humans are probably composite effects from damage to combinations of these functional modules. Interactions between these modules, either within posterior parietal cortex or downstream within frontal cortex, may account for more complex behaviors such as hand-eye coordination and reach-to-grasp.

Time course of the effect of the Muller-Lyer illusion on saccades and perceptual judgments

The amplitude of saccadic eye movements is affected by size illusions such as the Müller-Lyer illusion, but this effect varies highly between studies. Here we examine the origin of this variability by testing the influence of three temporal factors on the effect of the Müller-Lyer illusion: presentation time, response delay, and saccade latency. Subjects performed reflexive saccades, deferred saccades, and memory-guided saccades along the shaft of the illusion. We evaluated the time course of the saccadic illusion effects. We compared it to the influence of presentation time on the illusion effect in a perceptual judgment task. According to the "two visual systems hypothesis", visual perception and visual memory rely on a perceptual representation coded along the ventral "perception" pathway, which is affected by visual contextual illusions. Visuomotor actions, such as saccades, depend on the dorsal "action" pathway that is largely immune to illusions. In contrast with this hypothesis, our results show that the illusion affected both saccade amplitude and perceptual judgments with a similar time course. Presentation time of the Müller-Lyer illusion, not response delay or saccade latency, was the major factor in determining the size of the illusion effect. Longer presentation times resulted in smaller effects, suggesting that our visual representation is dynamic and becomes more accurate when we look at an object for a longer time before we act on it.

Object recognition using metric shape

Most previous studies of 3D shape perception have shown a general inability to visually perceive metric shape. In line with this, studies of object recognition have shown that only qualitative differences, not quantitative or metric ones can be used effectively for object recognition. Recently, Bingham and Lind (2008) found that large perspective changes (⩾45°) allow perception of metric shape and Lee and Bingham (2010) found that this, in turn, allowed accurate feedforward reaches-to-grasp objects varying in metric shape. We now investigated whether this information would allow accurate and effective recognition of objects that vary in respect to metric shape. Both judgment accuracies (d′) and reaction times confirmed that, with the availability of visual information in large perspective changes, recognition of objects using quantitative as compared to qualitative properties was equivalent in accuracy and speed of judgments. The ability to recognize objects based on their metric shape is, therefore, a function of the availability or unavailability of requisite visual information. These issues and results are discussed in the context of the Two Visual System hypothesis of Milner and Goodale (1995, 2006).

Distance Estimation Training: A Proposed Model of Transfer

Distance estimation is neither universally good nor universally bad. Rather, the level of accuracy generally depends on the task being performed. When misestimation does occur, training protocols have been implemented to improve one's ability to estimate distance. Unfortunately, results are mixed with regards to the effects of distance estimation training on subsequent task performance. Consequently, reliable statements regarding the conditions within which transfer will occur are limited. As a result, the ability to apply these mixed findings to real world situations is hampered. As a solution, a transfer model was created using the Two Visual Systems Hypothesis as a foundation. Interestingly, one area of the model lacks evidence. Specifically, the effects of perceptual-motor recalibration training on subsequent ventrally-guided distance estimation tasks are unclear.

Egocentric Spatial Representation in Action and Perception*

Neuropsychological findings used to motivate the “two visual systems” hypothesis have been taken to endanger a pair of widely accepted claims about spatial representation in conscious visual experience. The first is the claim that visual experience represents 3‐D space around the perceiver using an egocentric frame of reference. The second is the claim that there is a constitutive link between the spatial contents of visual experience and the perceiver’s bodily actions. In this paper, I review and assess three main sources of evidence for the two visual systems hypothesis. I argue that the best interpretation of the evidence is in fact consistent with both claims. I conclude with some brief remarks on the relation between visual consciousness and rational agency.

Perception, action, and experience: Unraveling the golden braid

Much of our human mental life looks to involve a seamless unfolding of perception, action and experience: a golden braid in which each element twines intimately with the rest. We see the very world we act in and we act in the world we see. But more than this, visual experience presents us with the world in a way apt for the control and fine guidance of action. Or so it seems. Milner and Goodale's [Milner, D., Goodale, M. (1995). The visual brain in action. Oxford: Oxford University Press; Milner, A., Goodale, M. (2006). Epilogue: Twelve years on. In Milner, A., Goodale, M. (Ed.), The visual brain in action (2nd ed., pp. 207–252). Oxford: Oxford University Press] influential work on the dual visual systems hypothesis casts doubt on certain versions of this intuitive vision. It does so by prising apart the twining strands of conscious visual perception and the fine control of visuomotor action. Such a bold proposal is of major interest both to cognitive science and philosophy. In what follows I first clarify the major claims that the bold proposal involves, then examine three sets of worries and objections. The first set concern some important matters of detail. The second set concern a certain kind of conceptual or philosophical worry to the effect that the perception/action model unfairly equates visual experience itself with what are in fact certain elements within visual experience. The third set concern the very idea of conscious experience as a well-defined conceptual or experimental target. I conclude that the boldest versions of the Dual Visual Systems (2VS) story underestimate the variety and richness of visual experience, but that the general picture of visual uptake as a fragmented, multi-stream, multipurpose adaptation is correct, and still revealing after all these years.

Memory mechanisms in grasping

The availability of visual information influences the execution of goal-directed movements. This is very prominent in memory conditions, where a delay is introduced between stimulus presentation and execution of the movement. The corresponding effects could be due to a decay of the visual information or to different processing mechanisms used for movements directed at visible (dorsal stream) and remembered (ventral stream) objects as proposed by the two visual systems hypothesis. In three experiments, the authors investigated grasping under full vision and three different delay conditions with increasing memory demands. Results indicate that the visuomotor information used for grasping decays rapidly. No evidence was found for qualitative changes in movement kinematics and the use of different representations for visually guided and memory guided movements. Findings rather suggest that delayed grasping is similar to grasping directed to larger objects under full vision. Therefore, the authors propose that grasping after a delay is guided by classic memory mechanisms and that this is reflected in an increasing maximum grip aperture in grasping.

ERGs and Psychophysical Thresholds in Students with Reading Discomfort

Symptoms of reading discomfort include unpleasant somatic and perceptual effects, such as eye-strain, headache, and blurred text, despite normal visual acuity. Reading discomfort has been proposed to be the result of increased noise in the visual system. Several studies have suggested that the symptoms can be minimized by having the subject wear colored filters. Thus, there may be abnormal neural processing in the cone pathways. This study measured L- and M-cone isolating (1) ERGs and (2) psychophysical thresholds in normal and reading discomfort subjects to determine if cone processing was abnormal in the reading discomfort population. Twenty-two normal and nineteen reading discomfort college students took part in this study. The normal subjects had Conlon survey scores within 0.5 SD of the mean and the reading discomfort subjects had scores >1.5 SD above the mean. ERGs were determined for a range (5 to 15%) of L- and M-cone contrasts. Slopes were determined for the L- and M-cone ERG amplitudes for each subject. Psychophysical thresholds were determined with a 2AFC technique combined with a 3-up and 1-down staircase procedure that terminated after 18 reversals occurred. The threshold was calculated as the average of the last 8 reversals. The average ERG slopes were not significantly different between the normal and reading discomfort groups (L-Cone, p = 0.086; M-Cone, p = 0.47). The L/M cone ratios for the slopes were not significantly different (p = 0.55). The log of the color contrast thresholds were not significantly different between the normal and reading discomfort groups (L-Cone, p = 0.97; M-Cone, p = 0.92). L- and M- cone ERG contrast gains and psychophysical estimates of color contrast thresholds were not significantly different. These results do not support the noisy visual system hypothesis of reading discomfort.

When does action resist visual illusion? The effect of Müller–Lyer stimuli on reflexive and voluntary saccades

The primate visual cortex exhibits two anatomically distinct pathways (dorsal and ventral). According to the "two visual systems hypothesis" (TVSH) of Milner and Goodale (The visual brain in action. Oxford University Press, Oxford, 1995), this anatomical distinction corresponds to a functional division of labor between vision-for-action (dorsal) and vision-for-perception (ventral). This proposal is supported by evidence that, in healthy volunteers, perceptual responses are affected by visual illusions, whereas motor responses to the same illusion-inducing stimuli are not. However, previously we have shown that the amplitude of saccadic eye movements is modified by the Müller-Lyer illusion in a similar manner as perceptual responses. Here we extend this finding to reflexive and voluntary (memory-guided) saccades. We show that both types of saccade can be strongly affected by the illusion. In our studies, the effect on reflexive saccades was comparable to that usually observed with verbal reports (an effect size of 22 +/- 8%), whereas the effect on voluntary saccades was smaller (11 +/- 11%). In addition, both types of saccade provide evidence for the scaling bias usually observed in perceptual responses. We suggest that previous studies may have employed methods that generally reduced the effect of the illusion. Interpretations of dissociations between reflexive and voluntary saccades in terms of the TVSH appear to be premature.