Traditional explanations of multistable visual phenomena (e.g. ambiguous figures, perceptual rivalry) suggest that the basis for spontaneous reversals in perception lies in antagonistic connectivity within the visual system. In this review, we suggest an alternative, albeit speculative, explanation for visual multistability – that spontaneous alternations reflect responses to active, programmed events initiated by brain areas that integrate sensory and non-sensory information to coordinate a diversity of behaviors. Much evidence suggests that perceptual reversals are themselves more closely related to the expression (...) of a behavior than to passive sensory responses: (1) they are initiated spontaneously, often voluntarily, and are influenced by subjective variables such as attention and mood; (2) the alternation process is greatly facilitated with practice and compromised by lesions in non-visual cortical areas; (3) the alternation process has temporal dynamics similar to those of spontaneously initiated behaviors; (4) functional imaging reveals that brain areas associated with a variety of cognitive behaviors are specifically activated when vision becomes unstable. In this scheme, reorganizations of activity throughout the visual cortex, concurrent with perceptual reversals, are initiated by higher, largely non-sensory brain centers. Such direct intervention in the processing of the sensory input by brain structures associated with planning and motor programming might serve an important role in perceptual organization, particularly in aspects related to selective attention. (shrink)

Correspondence should be addressed to David A. Leopold david.leopold@tuebingen.mpg.deDuring the viewing of certain patterns, widely known as ambiguous or puzzle figures, perception lapses into a sequence of spontaneous alternations, switching every few seconds between two or more visual interpretations of the stimulus. Although their nature and origin remain topics of debate, these stochastic switches are generally thought to be the automatic and inevitable consequence of viewing a pattern without a unique solution. We report here that in humans such perceptual alternations (...) can be slowed, and even brought to a standstill, if the visual stimulus is periodically removed from view. We also show, with a visual illusion, that this stabilizing effect hinges on perceptual disappearance rather than on actual removal of the stimulus. These findings indicate that uninterrupted subjective perception of an ambiguous pattern is required for the initiation of the brain-state changes underlying multistable vision.Visual perception involves coordination between sensory sampling of the world and active interpretation of the sensory data. Human perception of objects and scenes is normally stable and robust, but it falters when one is presented with patterns that are inherently ambiguous or contradictory. Under such conditions, vision lapses into a chain of continually alternating percepts, whereby a viable visual interpretation dominates for a few seconds and is then replaced by a rival interpretation. This multistable vision, or 'multistability', is thought to result from destabilization of fundamental visual mechanisms, and has offered valuable insights into how sensory patterns are actively organized and interpreted in the brain1, 2. Despite a great deal of recent research and interest in multistable perception, however, its neurophysiological underpinnings remain poorly understood. Physiological studies have suggested that disambiguation of ambiguous patterns. (shrink)

Both individually and as a collection, these essays will promote understanding and provoke further debate amongst students and established scholars alike.

Facial appearance changes with age and health affecting skin color as well as facial and head hair. Yet somehow the brain is able to see past shared structure and dynamic deformations to focus on subtle details that distinguish one face from another. This article argues that the brain takes an efficient approach to this problem using prior knowledge about the structure of faces in its analysis. It employs intrinsic norms to focus on subtle variations in the shared face configuration that (...) differentiate one face from another. The study reviews evidence that the brain uses multiple norms to extract face identity that these norms are shaped by visual experience, and that norm-based coding is well-suited to meeting the challenges of image-based face perception mentioned above. By encoding faces with reference to stored perceptual norms the visual system can focus on what is unique to each individual, allowing for the discrimination of thousands of faces despite their similarity. (shrink)

The Young Karl Marx is an innovative and important new study of Marx’s early writings. These writings provide the fascinating spectacle of a powerful and imaginative intellect wrestling with complex and significant issues, but they also present formidable interpretative obstacles to modern readers. David Leopold shows how an understanding of their intellectual and cultural context can illuminate the political dimension of these works. An erudite yet accessible discussion of Marx’s influences and targets frames the author’s critical engagement with Marx’s account (...) of the emergence, character, and (future) replacement of the modern state. This combination of historical and analytical approaches results in a sympathetic, but not uncritical, exploration of such fundamental themes as alienation, citizenship, community, antisemitism, and utopianism. The Young Karl Marx is a scholarly and original work which provides a radical and persuasive reinterpretation of Marx’s complex and often misunderstood views of German philosophy, modern politics, and human flourishing. (shrink)

“utopophobia” is a diverse and long-established phenomenon. Recent discussion of the notion of “realism” in political philosophy has illuminated one form that the fear of utopia can take—namely, suspicion and disapproval of normative standards that are unlikely ever to be achieved—but has not exhausted all that is of interest here.1 The present paper is concerned with a different variety of utopophobia: namely, the historically influential but not well-understood hostility of Karl Marx and Friedrich Engels toward the provision of plans and (...) blueprints of the ideal society of the future.2There seems little doubt about the existence of this Marxian utopophobia. (Note that I use the.. (shrink)

Background: Continuous viewing of ambiguous patterns is characterized by wavering perception that alternates between two or more equally valid visual solutions. However, when such patterns are viewed intermittently, either by repetitive presentation or by periodic closing of the eyes, perception can become locked or "frozen" in one configuration for several minutes at a time. One aspect of this stabilization is the possible existence of a perceptual memory that persists during periods in which the ambiguous stimulus is absent. Here, we use (...) a novel paradgim of temporally interleaved ambiguous stimuli to explore the nature of this memory, with particular regard to its potential impact on perceptual organization. Results: We found that the persistence of a perceptual configuration was robust to interposed visual patterns and, further, that at least three ambiguous patterns, when interleaved in time, could undergo parallel, stable time courses. Then, using an interleaved presentation paradigm, we established that the occasional reversal in one pattern could be coupled with that of its interleaved counterpart, and that this coupling was a function of the structural similarity between the patterns. Conclusions: We postulate that the stabilization observed with repetitive presentation of ambiguous patterns can be at least partially accounted for by processes that retain a recent perceptual interpretation, and we speculate that such memory may be important in natural vision. We further propose tha the interleaved paradigm introduced here may be of great value to gauge aspects of stimulus similarity that appeal to particular mechanisms of perceptual organization. (shrink)

Understanding how activity in the brain leads to a subjective percept is of great interest to philosophers and neuroscientists alike. In the last years, neurophysiological experiments have approached this problem directly by measuring neural signals in animals as they experience well-defined visual percepts. Stimuli in these studies are often inherently ambiguous, and thus rely upon the subjective report, generally from trained monkeys, to provide a measure of perception. By correlating activity levels in the brain to this report, one can speculate (...) on the role of individual neurons and groups of neurons in the formation and maintenance of a particular percept. However, in order to draw valid conclusions from such experiments, it is critical that the responses accurately and reliably reflect what is perceived. For this reason, a number of behavioural paradigms have been developed to control and evaluate the truthfulness of responses from behaving animals. Here we describe several approaches to optimizing the reliability of a monkey's perceptual report, and argue that their combination provides an invaluable approach in the study of subjective visual perception. (shrink)

This chapter discusses the account of ideology found in the writings of Karl Marx, and its fate in the subsequent Marxist tradition. Marx understood ideology as consisting of certain social ideas which periodically dominate in class-divided societies. More precisely, ideology was characterized as having a particular epistemological standing, social origin, and class function. In the subsequent Marxist tradition that ‘critical’ account was often displaced by non-critical, predominately ‘descriptive’, accounts of ideology. This historical pattern is exemplified by the writings of Antonio (...) Gramsci and Louis Althusser. This displacement of critical by descriptive accounts is portrayed as regrettable, not least because it involves a loss of the explanatory purchase and emancipatory potential found in Marx’s original account. (shrink)

INTRODUCTION It is a commonplace to observe that the left-Hegelian Max Stirner is little-known.gure in the history of political and philosophical thought. However, that obscurity should not be exaggerated. The author of Der Einzige und sein Eigentum is not only familiar to certain rather specialised and largely academic circles-those with an interest in Hegelianism, for example, or in the early intellectual development of Karl Marx -he is also, and more widely, known as a member of, and in.uence upon, the anarchist (...) tradition. Stirner's best-known work is often excerpted in anthologies of anarchist writings, and his name is regularly included as part of the modern pantheon in historically orientated surveys of anarchist thought. (shrink)

Gareth Stedman Jones has written a scholarly and interesting biography of Karl Marx, framed by the plausible idea that the ‘authentic’ Marx needs to be recovered from layers of 20th-century misinterpretation. The book focuses more on the political context than the intellectual content of Marx's ideas, and its treatment of the latter has some limitations. Not least, the author underestimates the complexity, interest, and relevance, of certain elements of Marx's thought.

Gareth Stedman Jones has written a scholarly and interesting biography of Karl Marx, framed by the plausible idea that the ‘authentic’ Marx needs to be recovered from layers of 20th-century misinterpretation. The book focuses more on the political context than the intellectual content of Marx's ideas, and its treatment of the latter has some limitations. Not least, the author underestimates the complexity, interest, and relevance, of certain elements of Marx's thought.

This article examines Friedrich Engels's little noticed communitarian sympathies, especially as expressed in his 1844 article 'kommunistischen Ansiedlungen'. These sympathies are in conflict with the considered and more critical view of communitarian socialism that he subsequently came to share with Karl Marx. I have four ambitions in the article: first, to provide some characterisation of this 'communitarian moment' in Engels's early intellectual evolution; second, to raise a number of worries about the argument of this particular article; third, to illuminate some (...) of the interesting variety in nineteenth-century communitarianism; and fourth, to insist on the complexity of questions about 'feasibility'. I maintain that Engels underestimates the variety of contemporary communitarianism, and that his appeal to the existence of intentional communities in America and Britain as proof of the feasibility of communism is unsuccessful. (shrink)