Neglect and Extinction

Block () highlights two experimental studies of neglect patients which, he contends, provide ‘dramatic evidence’ for unconscious seeing. In Block's hands this is the highly non-trivial thesis that seeing of the same fundamental kind as ordinary conscious seeing can occur outside of phenomenal consciousness. Block's case for it provides an excellent opportunity to consider a large body of research on clinical syndromes widely held to evidence unconscious perception. I begin by considering in detail the two studies of neglect to which (...) Block appeals. I show why their interpretation as evidence of unconscious seeing faces a series of local difficulties. I then explain how, even bracketing these issues, a long-standing but overlooked problem concerning our criterion for consciousness problematizes the appeal to both studies. I explain why this problem is especially pressing for Block given his view that phenomenal consciousness overflows access consciousness. I further show that it is epidemic—not only affecting all report-based studies of unconscious seeing in neglect, but also analogous studies of the condition most often alleged to show unconscious seeing, namely blindsight. (shrink)

Studies on the syndrome called ‘unilateral visual or spatial neglect’ have been used by philosophers in discussions concerning perceptual phenomenology. Nanay , based on spatial neglects studies, argued that the property of being suitable for action is part of the perceptual phenomenology of neglect patients. In this paper, I argue that the studies on visual neglect conducted thus far do not support Nanay’s thesis that when patients succeed in detecting the neglected object, it’s action properties are part of their perceptual (...) phenomenology; instead, the support the view that the patients consciously see low-level properties such as color and shape. In the first section, I discuss unilateral neglect and extinction. In the second section, I analyze Nanay’s argument. In the third section, I explain why Nanay’s thesis does not follow from the studies on visual neglect. Nanay argues that when neglect patients are cued with an action-property of an object and succeed in perceiving the object in the contralesional side they are phenomenally aware of an action-property of it but they are not phenomenally aware of its low-level properties. Since the patients detect the object, they must be phenomenally aware of some of its properties. Failing to see the low-level properties, the patients should be phenomenally aware is the action-property. Against this, I argue that research on spatial neglect shows that the patients come to see the low-level properties. I also explain why my discussion also supports the more general claim that the studies on neglect and extinction conducted thus far do not establish that the action-properties are part of the patients’ phenomenology. Finally, in section four, I examine a possible objection against my account. My arguments do not entail that the action properties are not part of perceptual phenomenology; only that the neglect studies do not establish this. (shrink)

One of the most compelling questions still unanswered in neuroscience is how consciousness arises. In this article, we examine visual processing, the parietal lobe, and contralateral neglect syndrome as a window into consciousness and how the brain functions as the mind and we introduce a mechanism for the processing of visual information and its role in consciousness. We propose that consciousness arises from integration of information from throughout the body and brain by the thalamus and that the thalamus reimages visual (...) and other sensory information from throughout the cortex in a default three-dimensional space in the mind. We further suggest that the thalamus generates a dynamic default three-dimensional space by integrating processed information from corticothalamic feedback loops, creating an infrastructure that may form the basis of our consciousness. Further experimental evidence is needed to examine and support this hypothesis, the role of the thalamus, and to further elucidate the mechanism of consciousness. (shrink)

I am looking at an apple. The apple has a lot of properties and some, but not all, of these are part of my phenomenology at this moment: I am aware of these properties. And some, but not all, of these properties that I am aware of are part of my perceptual (or sensory) phenomenology. If I am attending to the apple’s color, this property will be part of my perceptual phenomenology. The property of being a granny smith apple from (...) Chile is unlikely to be part of my perceptual phenomenology. Here are two problems for anyone who is interested in conscious experience in general, and perceptual experience in particular: (a) How can we tell which properties are part of our phenomenology and which ones are not? (b) How can we tell which properties are part of our perceptual phenomenology and which ones are part of our non-perceptual phenomenology? I will focus on (b) in this paper. My aim is twofold: I propose a methodology for answering the question of which properties are part of our perceptual phenomenology and I provide an example for how this methodology could be applied. (shrink)

Visual neglect has been associated with an imbalance in the level of activity in the saccadic system: activity in the contralesional field is suppressed, which makes target selection unlikely. We recorded eye movements of a patient with hemispatial neglect and a group of healthy participants during an oculomotor distractor paradigm. Results showed that the interfering effects of a distractor were very strong when presented in her ipsilesional visual field. However, when the distractor was presented in her contralesional field, there were (...) no interfering effects when the target was presented in her ipsilesional field. These findings could not be explained by the presence of a visual field defect as revealed by the results of two hemianopic patients. Our results are in line with an imbalance in the level of activity in the saccadic system in visual neglect because visual elements presented in the contralesional field did not compete for saccadic selection. (shrink)

Focusing on the individual's internal cognitive architecture, McKay & Dennett (M&D) provide an incomplete analysis because they neglect the crucial role played by the external environment in producing misbeliefs and determining whether those misbeliefs are adaptive. In some environments, positive illusions are not adaptive. Further, misbeliefs often arise because the environment commonly fails to provide crucial information needed to form accurate judgments.

The tendency to neglect base-rates in judgment under uncertainty may be as Barbey & Sloman (B&S) suggest, but it is neither inevitable (as they document; see also Koehler 1996) nor unique. Here we would like to point out another line of evidence connecting ecological rationality to dual processes, the failure of individuals to appropriately judge cumulative probability.

Barbey & Sloman's (B&S's) base-rate respect model is anticipated by Reyna's denominator neglect model. There are parallels at three levels: (a) explanations are grounded in a general cognitive theory (rather than in domain-specific ideas); (b) problem structure is treated as a key source of reasoning errors; and most importantly, (c) nested set relations are seen as the cause of base-rate neglect.

We believe that when assessing the likelihood of uncertain events, statistically unsophisticated people utilize a coarse internal scale that only has a limited number of categories. The success of the nested sets hypothesis may lie in its ability to provide an appropriate set structure of the problem by reducing the computational demands.

Ego-justifying, group-justifying, and system-justifying motivations contribute to base-rate respect. People tend to neglect (and use) base rates when doing so allows them to draw desired conclusions about matters such as their health, the traits of their in-groups, and the fairness of the social system. Such motivations can moderate whether people rely on the rule-based versus associative strategies identified by Barbey & Sloman (B&S).

While improving the theoretical account of base-rate neglect, Barbey & Sloman's (B&S's) target article suffers from affect neglect by failing to consider the fundamental role of emotional processes in decisions. We illustrate how affective influences are fundamental to decision making, and discuss how the dual process model can be a useful framework for understanding hot and cold cognition in reasoning.

Homo sapiens have evolved a dual-process cognitive architecture that is adaptive but prone to systematic errors. Fuzzy-trace theory predicts that nested or overlapping class-inclusion relations create processing interference, resulting in denominator neglect: behaving as if one ignores marginal denominators in a 2 × 2 table. Ignoring marginal denominators leads to fallacies in base-rate problems and conjunctive and disjunctive probability estimates.

As shown by neuroscientific evidence, neglect may occur without elementary sensorimotor impairments. The deficit is to be found at a higher, more abstract level of representation, which prevents the patient not only from seeing, but from conceiving the contralesional space. By analysing a series of neuropsychological results, in this paper we suggest a crucial role of time for the construction of a world: on this basis, we try to explain how it is possible that half the ontology gets lost. The (...) analysis of the ontological implication of neglect will allow us to shed light on manifestations of the pathology apparently disconnected. (shrink)