Conscious Vision for Action Versus Unconscious Vision for Action?

David Milner and Melvyn Goodale’s dissociation hypothesis is commonly taken to state that there are two functionally specialized cortical streams of visual processing originating in striate (V1) cortex: a dorsal, action‐related “unconscious” stream and a ventral, perception‐related “conscious” stream. As Milner and Goodale acknowledge, findings from blindsight studies suggest a more sophisticated picture that replaces the distinction between unconscious vision for action and conscious vision for perception with a tripartite division between unconscious vision for action, conscious vision for perception, and unconscious vision for perception. The combination excluded by the tripartite division is the possibility of conscious vision for action. But are there good grounds for concluding that there is no conscious vision for action? There is now overwhelming evidence that illusions and perceived size can have a significant effect on action ( Bruno & Franz, 2009 ; Dassonville & Bala, 2004 ; Franz & Gegenfurtner, 2008 ; McIntosh & Lashley, 2008 ). There is also suggestive evidence that any sophisticated visual behavior requires collaboration between the two visual streams at every stage of the process ( Schenk & McIntosh, 2010 ). I nonetheless want to make a case for the tripartite division between unconscious vision for action, conscious vision for perception, and unconscious vision for perception. My aim here is not to refute the evidence showing that conscious vision can affect action but rather to argue (a) that we cannot gain cognitive access to action‐guiding dorsal stream representations, and (b) that these representations do not correlate with phenomenal consciousness. This vindicates the semi‐conservative view that the dissociation hypothesis is best understood as a tripartite division.     

Are there unconscious perceptual processes?

Blindsight and vision for action seem to be exemplars of unconscious visual processes. However, researchers have recently argued that blindsight is not really a kind of unconscious vision but is rather severely degraded conscious vision. Morten Overgaard and colleagues have recently developed new methods for measuring the visibility of visual stimuli. Studies using these methods show that reported clarity of visual stimuli correlates with accuracy in both normal individuals and blindsight patients. Vision for action has also come under scrutiny. Recent findings seem to show that information processed by the dorsal stream for online action contributes to visual awareness. Some interpret these results as showing that some dorsal stream processes are conscious visual processes (e.g., Gallese, 2007; Jacob & Jeannerod, 2003). The aim of this paper is to provide new support for the more traditional view that blindsight and vision for action are genuinely unconscious perceptual processes. I argue that individuals with blindsight do not have access to the kind of purely qualitative color and size information which normal individuals do. So, even though people with blindsight have a kind of cognitive consciousness, visual information processing in blindsight patients is not associated with a distinctly visual phenomenology. I argue further that while dorsal stream processing seems to contribute to visual awareness, only information processed by the early dorsal stream (V1, V2, and V3) is broadcast to working memory. Information processed by later parts of the dorsal stream (the parietal lobe) never reaches working memory and hence does not correlate with phenomenal awareness. I conclude that both blindsight and vision for action are genuinely unconscious visual processes.     

Implicit biases in visually guided action

For almost half a century dual-stream advocates have vigorously defended the view that there are two functionally specialized cortical streams of visual processing originating in the primary visual cortex: a ventral, perception-related ‘conscious’ stream and a dorsal, action-related ‘unconscious’ stream. They furthermore maintain that the perceptual and memory systems in the ventral stream are relatively shielded from the action system in the dorsal stream. In recent years, this view has come under scrutiny. Evidence points to two overlapping action pathways: a dorso-dorsal pathway that calculates features of the object to be acted on, and a ventro-dorsal pathway that transmits stored information about skilled object use from the ventral stream to the dorso-dorsal pathway. This evidence suggests that stored information may exert significantly more influence on visually guided action than hitherto assumed. I argue that this, in turn, supports the notion of skilled automatic action that is nonetheless agential. My focus here will be on actions influenced by implicit biases (stereotypes/prejudices). Action that is biased in this way, I argue, is in an important sense intentional and agential.

     

The neural-cognitive basis of the Jamesian stream of thought

William James described the stream of thought as having two components: (1) a nucleus of highly conscious, often perceptual material; and (2) a fringe of dimly felt contextual information that controls the entry of information into the nucleus and guides the progression of internally directed thought. Here I examine the neural and cognitive correlates of this phenomenology. A survey of the cognitive neuroscience literature suggests that the nucleus corresponds to a dynamic global buffer formed by interactions between different regions of the brain, while the fringe corresponds to a set of mechanisms in the frontal and medial temporal lobes that control the contents of this global buffer. A consequence of this account is that there might be conscious imagistic representations that are not part of the nucleus. I argue that phenomenology can be linked to psychology and neuroscience and a meaningful way that illuminates both.     

Cognitive phenomenology and conscious thought

How does mental content feature in conscious thought? I first argue that for a thought to be conscious the content of that thought must conscious, and that one has to appeal to cognitive phenomenology to give an adequate account of what it is for the content of a thought to be conscious. Sensory phenomenology cannot do the job. If one claims that the content of a conscious thought is unconscious, one is really claiming that there is no such thing as conscious thought. So one must either accept that there is such a thing as cognitive phenomenology, or deny the existence of conscious thought. Once it is clear that conscious thought requires cognitive phenomenology, there is a pressing question about the exact relationship between a thought’s cognitive phenomenological properties and its content. I conclude with a discussion of the nature of this relationship.     

Reference,perception, and attention

I examine John Campbell’s claim that the determination of the reference of a perceptual demonstrative requires conscious visual object-based selective attention. I argue that although Campbell’s claim to the effect that, first, a complex binding parameter is needed to establish the referent of a perceptual demonstrative, and, second, that this referent is determined independently of, and before, the application of sortals is correct, this binding parameter does not require object-based attention for its construction. If object-based attention were indeed required then the determination of the referent would necessarily involve the application of sortal concepts, since object-based attention initiates top-down cognitive effects on visual processing. I also examine Mohan Matthen’s claim that reference to objects is established only through the visual processing in the dorsal visual stream and argue that although it is true that processing in the dorsal stream can determine reference, a thesis that goes against Campbell’s view that the determination of the referent requires conscious attention, processing along the ventral visual stream can also establish the reference of perceptual demonstratives. It also claim that Matthen’s account of dorsal processing underestimates the kind of information processed along the dorsal stream and this has some implications regarding perceptual demonstratives reference fixing.

Testing the dorsal stream attention hypothesis: Electrophysiological correlates and the effects of ventral stream damage

The roles of dorsal and ventral processing streams in visual orienting and conscious perception were examined in two experiments. The first employed high density EEG with source localization. The second comprised a neuropsychological case study. Visual orienting was assessed with an attention procedure, where peripheral letters cued participants towards a target location. In the perception procedure participants responded to the same letters by performing an explicit conscious discrimination. In Experiment 1, the peripheral letters elicited rapid dorsal stream activation in the attention procedure, and this activation preceded top-down enhancement of target processing in occipital cortex. In the perception procedure early ventral stream activation was seen. In addition, peripheral letters elicited an “early directing attention negativity” (EDAN) over parietal recording sites in the attention procedure, but not in the perception procedure. In Experiment 2, a patient with a bilateral ventral stream lesion but preserved dorsal stream function showed clear disruption to performance in the perception procedure, whilst exhibiting a normal visual orienting effect in the attention procedure. Taken together these findings (1) highlight the distinct roles of the dorsal and ventral streams in attention and perception, and (2) suggest how these streams might interact, via reentrant effects of attention on perceptual processing.     

Unconscious vision and executive control: How unconscious processing and conscious action control interact

Research on unconscious or unaware vision has demonstrated that unconscious processing can be flexibly adapted to the current goals of human agents. The present review focuses on one area of research, masked visual priming. This method uses visual stimuli presented in a temporal sequence to lower the visibility of one of these stimuli. In this way, a stimulus can be masked and even rendered invisible. Despite its invisibility, a masked stimulus if used as a prime can influence a variety of executive functions, such as response activation, semantic processing, or attention shifting. There are also limitations on the processing of masked primes. While masked priming research demonstrates the top-down dependent usage of unconscious vision during task-set execution it also highlights that the set-up of a new task-set depends on conscious vision as its input. This basic distinction captures a major qualitative difference between conscious and unconscious vision.     

Defining the cortical visual systems: "what", "where", and "how"

The visual system historically has been defined as consisting of at least two broad subsystems subserving object and spatial vision. These visual processing streams have been organized both structurally as two distinct pathways in the brain, and functionally for the types of tasks that they mediate. The classic definition by Ungerleider and Mishkin labeled a ventral "what" stream to process object information and a dorsal "where" stream to process spatial information. More recently, Goodale and Milner redefined the two visual systems with a focus on the different ways in which visual information is transformed for different goals. They relabeled the dorsal stream as a "how" system for transforming visual information using an egocentric frame of reference in preparation for direct action. This paper reviews recent research from psychophysics, neurophysiology, neuropsychology and neuroimaging to define the roles of the ventral and dorsal visual processing streams. We discuss a possible solution that allows for both "where" and "how" systems that are functionally and structurally organized within the posterior parietal lobe.     

A multi-stage account of binding in vision: Neuropsychological evidence

I review neuropsychological evidence on the problems patients can have in binding together the attributes of visual stimuli, following brain damage. The evidence indicates that there can be several kinds of binding deficit in patients. Damage to early visual processing within the ventral visual stream can disrupt the binding of contours into shapes, though the binding of form elements into contours can still operate. This suggests that the process of binding elements into contour is distinct from the process of binding contours into shapes. The latter form of binding seems to operate within the ventral visual system. In addition, damage to the parietal lobe can disrupt the binding of shape to surface information about objects, even when the binding of elements into contours, and contours into shapes, seems to be preserved. These findings are consistent with a multi-stage account of binding in vision, which distinguishes between the processes involved in binding shape information (in the ventral visual stream) and the processes involved in binding shape and surface detail (involving interactions between the ventral and dorsal streams). In addition, I present evidence indicating that a further, transient form of binding can take place, based on stimuli having common visual onsets. I discuss the relations between these different forms of binding.     

Dorsal stream activation during retrieval of object size and shape

We investigated dorsal visual stream involvement in the retrieval of a variety of visual attributes of common objects, using functional magnetic resonance imaging. Seven subjects made binary decisions about the shape, color, and size of named objects during scanning. Bilateral parietal activity was significantly greater during retrieval of shape and size information than during retrieval of color information. Consistent with a domain-specific distributed model of semantic organization, the finding that dorsal stream activity is associated with size and shape retrieval, as compared with color retrieval, may indicate that both size and shape information are learned partly through dorsally mediated processes, such as visually guided grasping. These results demonstrate that both visual-processing streams (i.e., the ventral “what” pathway and the dorsal “where” pathway) are involved in the storage and/or retrieval of knowledge of object appearance but that, just as in vision, these two pathways may play different roles in conceptual processing.     

Selection of Decision Strategies After Conscious and Unconscious Thought

It is commonly assumed that the use of simple, non‐compensatory strategies is especially pronounced in memory‐based decisions, where information costs are high. At the same time, there is evidence that in memory‐based decisions, a compensatory processing of attributes is facilitated when the processing occurs unconsciously rather than consciously. We applied a strategy classification approach—developed in research on non‐compensatory heuristics—to test two key tenets of unconscious thought theory: the capacity principle and the weighting principle. Participants memorized attribute information about cars and were subsequently either directed to or diverted from thinking consciously about their preferences between the cars (conscious versus unconscious thought). Then, participants indicated in pair‐wise choices which car they would prefer and were classified (based on their choices) as using either one of two compensatory strategies (equal weight or weighted additive) or a non‐compensatory strategy (lexicographic heuristic). In line with the capacity principle, the number of participants best described by a compensatory strategy (the equal‐weight strategy) tended to be higher after unconscious thought than after conscious thought, whereas the number of participants best described by the lexicographic heuristic tended to be lower. Inconsistent with the weighting principle, participants in the unconscious thought condition were better described by the equal‐weight strategy than by the weighted‐additive strategy. In Experiment 2, in which participants were not instructed to form an impression while learning the attribute information, the use of the equal‐weight strategy was not more prevalent after unconscious thought. Copyright © 2013 John Wiley & Sons, Ltd.     

Perceptual consciousness plays no epistemic role

It is often assumed that perceptual experience provides evidence about the external world. But much perception can occur unconsciously, as in cases of masked priming or blindsight. Does unconscious perception provide evidence as well? Many theorists maintain that it cannot, holding that perceptual experience provides evidence in virtue of its conscious character. Against such views, I challenge here both the necessity and, perhaps more controversially, the sufficiency of consciousness for perception to provide evidence about the external world. In addition to motivating and defending the idea that unconscious perception can and does often provide evidence, I observe that whether or not perceptual phenomenology is relevant to the evidentiary status of perception depends on the nature of consciousness. And I argue that a well‐supported theory of consciousness—higher‐order thought theory—invites a striking conclusion: that perceptual phenomenology is not on its own sufficient to provide for evidence of the external world.     

Visual consciousness revisited: magnocellular and parvocellular contributions to conscious and nonconscious vision

Current theoretical approaches to consciousness and vision associate the dorsal cortical pathway, in which magnocellular (M) input is dominant, with nonconscious visual processing and the ventral cortical pathway, in which parvocellular (P) input is dominant, with conscious visual processing. We explored the known differences between M and P contrast-response functions to investigate the roles of these channels in vision. Simulations of contrast-dependent priming revealed that priming effects obtained with unmasked, visible primes were best modeled by equations characteristic of M channel responses, whereas priming effects obtained with masked, invisible primes were best modeled by equations characteristic of P channel responses. In the context of current theoretical approaches to conscious and nonconscious processing, our results indicate a surprisingly significant role of M channels in conscious vision. In a broader discussion of the role of M channels in vision, we propose a neurophysiologically plausible interpretation of the present results: M channels indirectly contribute to conscious object vision via top-down modulation of reentrant activity in the ventral object-recognition stream.     

Weighing the evidence for a dorsal processing bias under continuous flash suppression

With the introduction of continuous flash suppression (CFS) as a method to render stimuli invisible and study unconscious visual processing, a novel hypothesis has gained popularity. It states that processes typically ascribed to the dorsal visual stream can escape CFS and remain functional, while ventral stream processes are suppressed when stimuli are invisible under CFS. This notion of a CFS-specific “dorsal processing bias” has been argued to be in line with core characteristics of the influential dual-stream hypothesis of visual processing which proposes a dissociation between dorsally mediated vision-for-action and ventrally mediated vision-for-perception. Here, we provide an overview of neuroimaging and behavioral studies that either examine this dorsal processing bias or base their conclusions on it. We show that both evidence for preserved ventral processing as well as lack of dorsal processing can be found in studies using CFS. To reconcile the diverging results, differences in the paradigms and their effects are worthy of future research. We conclude that given the current level of information a dorsal processing bias under CFS cannot be universally assumed.     

无意识思维:理论、质疑与回应

Dijksterhuis等人发现在解决复杂问题时,无意识思维的加工结果优于有意识思维,并据此提出了无意识思维理论。本文介绍了支持无意识思维理论的基本实验证据,质疑无意识思维的相关研究及对质疑的回应研究。未来研究应重点关注改进无意识思维研究范式和寻找更多影响无意识思维效应的中介变量,无意识思维加工结果如何上升到有意识层面,无意识思维的加工方式以及其在真实和高风险任务情境中的应用。     

Nietzsche on the Nature of the Unconscious

Abstract

This paper argues that Nietzsche develops a novel and compelling account of the distinction between conscious and unconscious mental states: he argues that conscious mental states are those with conceptual content, whereas unconscious mental states are those with nonconceptual content. I show that Nietzsche’s puzzling claim that consciousness is ‘superficial’ and ‘falsifying’ can be given a straightforward explanation if we accept this understanding of the conscious/unconscious distinction. I originally defended this view in my ‘Nietzsche’s Theory of Mind: Consciousness and Conceptualization’ (2005, European Journal of Philosophy 13: 1–31); since then, the view has come under criticism on several fronts. Brian Leiter and others suggest that there is not enough textual evidence for the view. In addition, Leiter, Mattia Riccardi and Tsarina Doyle argue that, rather than aligning the conscious/unconscious distinction with the conceptual/nonconceptual distinction, Nietzsche endorses a higher-order thought model of consciousness. Riccardi also objects that Nietzsche must treat some unconscious mental states as conceptual. In this essay, I defend the interpretation in light of these objections. I provide new textual evidence for the interpretation, show that Nietzsche extracted aspects of the view from Schopenhauer’s work on consciousness, consider the possibility that Nietzsche endorses a higher-order thought theory, and respond to Riccardi’s objection.     

Towards a New Feeling Theory of Emotion

According to the old feeling theory of emotion, an emotion is just a feeling: a conscious experience with a characteristic phenomenal character. This theory is widely dismissed in contemporary discussions of emotion as hopelessly naïve. In particular, it is thought to suffer from two fatal drawbacks: its inability to account for the cognitive dimension of emotion (which is thought to go beyond the phenomenal dimension), and its inability to accommodate unconscious emotions (which, of course, lack any phenomenal character). In this paper, I argue that the old feeling theory is in reality only a pair of modifications removed from a highly plausible account of the nature of emotion that retains the essential connection between emotion and feeling. These modifications are, moreover, motivated by recent developments in work on phenomenal consciousness. The first development is the rising recognition of a phenomenal character proper to cognition—so‐called cognitive phenomenology. The second is the gathering momentum behind various ‘connection principles’ that specify some connection that a given state must bear to phenomenally conscious states in order to qualify as mental. These developments make it possible to formulate a new feeling theory of emotion, which would overcome the two fatal drawbacks of the old feeling theory. According to the new feeling theory, an emotion is a mental state that bears the right connection to conscious experiences with the right phenomenal character (involving, among other elements, a cognitive phenomenology).     

Four empirical tests of Unconscious Thought Theory

According to Unconscious Thought Theory, people make better decisions after unconscious than after conscious thought (Dijksterhuis, Bos, Nordgren, & van Baaren, 2006a). Unconscious Thought Theory yields four specific predictions. First, an exact replication of Dijksterhuis et al. (2006a) study should indicate that unconscious decisions are superior to conscious decisions. Second, decisions should improve with duration of conscious thought. Third, unconscious decisions should be superior to conscious decisions, even if unconscious decisions are deliberated while having access to information. Fourth, unconscious decisions should be based on a weighting strategy. We report results of four studies, featuring 480 participants, that yield no evidence in favor of these predictions. Therefore our findings cast doubt on Unconscious Thought Theory and its advice to base decisions on unconscious thought. The results of our studies suggest that it is better to base decisions on conscious thought while having access to information.     

Dorsal and ventral streams: a framework for understanding aspects of the functional anatomy of language

Despite intensive work on language-brain relations, and a fairly impressive accumulation of knowledge over the last several decades, there has been little progress in developing large-scale models of the functional anatomy of language that integrate neuropsychological, neuroimaging, and psycholinguistic data. Drawing on relatively recent developments in the cortical organization of vision, and on data from a variety of sources, we propose a new framework for understanding aspects of the functional anatomy of language which moves towards remedying this situation. The framework posits that early cortical stages of speech perception involve auditory fields in the superior temporal gyrus bilaterally (although asymmetrically). This cortical processing system then diverges into two broad processing streams, a ventral stream, which is involved in mapping sound onto meaning, and a dorsal stream, which is involved in mapping sound onto articulatory-based representations. The ventral stream projects ventro-laterally toward inferior posterior temporal cortex (posterior middle temporal gyrus) which serves as an interface between sound-based representations of speech in the superior temporal gyrus (again bilaterally) and widely distributed conceptual representations. The dorsal stream projects dorso-posteriorly involving a region in the posterior Sylvian fissure at the parietal-temporal boundary (area Spt), and ultimately projecting to frontal regions. This network provides a mechanism for the development and maintenance of "parity" between auditory and motor representations of speech. Although the proposed dorsal stream represents a very tight connection between processes involved in speech perception and speech production, it does not appear to be a critical component of the speech perception process under normal (ecologically natural) listening conditions, that is, when speech input is mapped onto a conceptual representation. We also propose some degree of bi-directionality in both the dorsal and ventral pathways. We discuss some recent empirical tests of this framework that utilize a range of methods. We also show how damage to different components of this framework can account for the major symptom clusters of the fluent aphasias, and discuss some recent evidence concerning how sentence-level processing might be integrated into the framework.