Miller (1956) summarized evidence that people can remember about seven chunks in short-term memory (STM) tasks. However, that number was meant more as a rough estimate and a rhetorical device than as a real capacity limit. Others have since suggested that there is a more precise capacity limit, but that it is only three to five chunks. The present target article brings together a wide variety of data on capacity limits suggesting that the smaller capacity limit is real. Capacity limits (...) will be useful in analyses of information processing only if the boundary conditions for observing them can be carefully described. Four basic conditions in which chunks can be identified and capacity limits can accordingly be observed are: (1) when information overload limits chunks to individual stimulus items, (2) when other steps are taken specifically to block the recoding of stimulus items into larger chunks, (3) in performance discontinuities caused by the capacity limit, and (4) in various indirect effects of the capacity limit. Under these conditions, rehearsal and long-term memory cannot be used to combine stimulus items into chunks of an unknown size; nor can storage mechanisms that are not capacity-limited, such as sensory memory, allow the capacity-limited storage mechanism to be refilled during recall. A single, central capacity limit averaging about four chunks is implicated along with other, noncapacity-limited sources. The pure STM capacity limit expressed in chunks is distinguished from compound STM limits obtained when the number of separately held chunks is unclear. Reasons why pure capacity estimates fall within a narrow range are discussed and a capacity limit for the focus of attention is proposed. Key Words: attention; enumeration; information chunks; memory capacity; processing capacity; processing channels; serial recall; short-term memory; storage capacity; verbal recall; working memory capacity. (shrink)

It is the central hypothesis of this paper that the mental states commonly referred to as altered states of consciousness are principally due to transient prefrontal cortex deregulation. Supportive evidence from psychological and neuroscientific studies of dreaming, endurance running, meditation, daydreaming, hypnosis, and various drug-induced states is presented and integrated. It is proposed that transient hypofrontality is the unifying feature of all altered states and that the phenomenological uniqueness of each state is the result of the differential viability of various (...) frontal circuits. Using an evolutionary approach, consciousness is conceptualized as hierarchically ordered cognitive function. Higher-order structures perform increasingly integrative functions and thus contribute more sophisticated content. Although this implies a holistic approach to consciousness, such a functional hierarchy localizes the most sophisticated layers of consciousness in the zenithal higher-order structure: the prefrontal cortex. The hallmark of altered states of consciousness is the subtle modification of behavioral and cognitive functions that are typically ascribed to the prefrontal cortex. The theoretical framework presented yields a number of testable hypotheses. (shrink)

Working memory limits are best defined in terms of the complexity of the relations that can be processed in parallel. Complexity is defined as the number of related dimensions or sources of variation. A unary relation has one argument and one source of variation; its argument can be instantiated in only one way at a time. A binary relation has two arguments, two sources of variation, and two instantiations, and so on. Dimensionality is related to the number of chunks, because (...) both attributes on dimensions and chunks are independent units of information of arbitrary size. Studies of working memory limits suggest that there is a soft limit corresponding to the parallel processing of one quaternary relation. More complex concepts are processed by or In segmentation, tasks are broken into components that do not exceed processing capacity and can be processed serially. In conceptual chunking, representations are to reduce their dimensionality and hence their processing load, but at the cost of making some relational information inaccessible. Neural net models of relational representations show that relations with more arguments have a higher computational cost that coincides with experimental findings on higher processing loads in humans. Relational complexity is related to processing load in reasoning and sentence comprehension and can distinguish between the capacities of higher species. The complexity of relations processed by children increases with age. Implications for neural net models and theories of cognition and cognitive development are discussed. (shrink)

The implicit-explicit distinction is applied to knowledge representations. Knowledge is taken to be an attitude towards a proposition which is true. The proposition itself predicates a property to some entity. A number of ways in which knowledge can be implicit or explicit emerge. If a higher aspect is known explicitly then each lower one must also be known explicitly. This partial hierarchy reduces the number of ways in which knowledge can be explicit. In the most important type of implicit knowledge, (...) representations merely reflect the property of objects or events without predicating them of any particular entity The dearest cases of explicit knowledge of a fact are representations of one's own attitude of knowing that fact. These distinctions are discussed in their relationship to similar distinctions such as procedural-declarative, conscious unconscious, verbalizable-nonverbalizable, direct-indirect tests, and automatic voluntary control. This is followed by an outline of how these distinctions can be used to integrate and relate the often divergent uses of the implicit-explicit distinction in different research areas. We illustrate this for visual perception, memory, cognitive development, and artificial grammar learning. (shrink)

Je lui ai associÉ un court extrait d'une revue de questions portant sur le même thème. Implicit memory is revealed when previous experiences facilitate perf on a task that does not require conscious or intentional recollection of those expces. Explicit memory is revealed when perf on a task requires conscious recolelction of previous expces. Il s'agit de defs descriptives qui n'impliquent pas l'existence de deux systs de mÉmo sÉparÉs. Historiquement Descartes est le premier ˆ faire mention de phÉnomènes de mÉmo (...) implicites, Leibniz, Maine de Biran, Bergson en ont Également parlÉ. Korsakoff (1889) avec ses travaux sur les amnÉsiques montre qu'ils sont capables d'utiliser de l'info qu'ils ont acquises dans des Épisodes rÉcents sans pour autant manifester le moindre souvenir de l'Épisode. L'interprÉtation de ces phÉnomènes Était alors que ça renvoyait ˆ des traces en mÉmoire trop tÉnues pour accèder jusqu'au champ de la conscience. Cette interprÉtation va pouvoir être ÉcartÉe par les travaux rÉcents. Thorndike a Également conduit un nbre important de travaux sur MI. Les trauvaux un peu plus rÉcents ont montrÉ qu'un apprentissage antÉrieur pouvait faciliter une perfce sans qu'il y ait ref explicite à l'Épisode d'apprentissage. On a montrÉ aussi l'effet de stimuli subliminaux, qui en tant que tels ne peuvent pas être rappelÉs consciemment, mais qui influencent la conduite ou les jugts ultÉrieurs. Par ex, la prÉsentation de formes sur des temps très courts qui excluent la possibilitÉ d'une perception consciente influence significativement lechoix de formes dans une pÉreuve ultÉrieure de choix forcÉs où les sjts doivent indiquer la forme qu'il prÉfère entre deux. Ils choisissent prÉfÉrentiellement celles qui leur ont ÉtÉ prÉsentÉes de manière subliminale. De même Bargh et al. ont montrÉ que des sjts soumis de manière subliminale ˆ des mots hostiles portent ultÉrieurement des jugts plus nÉgatifs sur une personne target. Il ya Également eu des travaux sur l'apprsge ou le condt without awareness en particulier apprsge implicite de règles de grammaire (ie le sjt peut construire de nouvelles phrases conformes ˆ la syntaxe de celles qui lui ont ÉtÉ prÉsentÉes sans pour autant petre capables d'noncer les règles de grammaire qu'il utilise) Rem: N'est ce pas un pbe de typemÉtacognition??? Enfin, tous les travaux sur le priming sont des elts en faveur de MI: Facilitation in the processing of a stimulus as a function of a recent encounter with the same stimulus. Type de perfce sur lesquels les effets de priming ont ÉtÉ dÉmontrÉs: -T‰ches de dÉcision lexicale: Le sjt doit dire si la cha"ne de caractères qu'on lui prÉsente est un mot ou pas: Le temps de latence est beaucoup plus court si la cha"ne a dÉjˆ ÉtÉ prÉsentÉe une première fois. -Mesures de temps d'identification de mots en rpÉsentation tachitoscopiques -ComplÉmentation de mots: les sjts ont tendance ˆ complÉter pour crÉer les mots qui leur ont ÉtÉ prÉsentÉs antÉrieurement. L'intÉrêt pour le paradigme de priming se retouve chez les gens qui s'intÉressent ˆ: -reconnaissance de mots et organisation lexicale. les effets de priming permettent de faire des hyps sur l'accès lexical et la reprÉsentation. -M. Épisodique: travux sur les amnÉsiques qui ne se souviennent pas qu'on vient de leur prÉsenter des mots mais qui manifestent une mÉmoire implicite lorsqu'on leur fait faire de la complÉmentation de mots. DISSOCIATION ENTRE M.I. ET M EXPLICITE 1-Si de nombreux travaux montrent que la M explicite est influencÉe par le travail d'Élaboration (profondeur de traitement) en jeu pendant la première phase d'Étude des stimuli, il semble que la MI ne le soit pas. 2-Le changt de modalitÉ (par ex auditif -> visuel) entre la phase d'Étude et la phase de test provoque une attÉnuation importante de l'effet de priming si le test est un test de MI mais pas si c'est un test de ME. 3-Les effets de primings persistent assez largement sur plusieurs jours ce qui n'est pas le cas des perfces ˆ une Épreuve de reconnaissance. 4-Les perfces sur des tests de MI ne semblent pas influencÉes par des manipulations d'interfÉrences proactives ou rÉtroactives dont on sait qu'elles influencent les perfces en ME. 5-Absce de corrÉlation entre perfces ˆ des tests de reconnaissance et perfces ˆ une Épreuve de complÉmentation de mots. SIMILARITES ENTRE PRIMING ET REMEMBERING 1- A certaines conditions les durÉes de rÉtention on des effets parallèles sur les effets de priming et les mesures de ME (REm: en partie contradictoire avec 3 ci dessus) 2-La manipulation du contexte de la liste lors de la phase d'Étude affecte ˆ la fois les perfces en reconnaissance et en identification de mots. 3- ME et MI sont influencÉes par des associations nouvellement acquises entre des paires de mots non reliÉes (Rem: contradictoires avec 4 ci dessus ??) 4- Rem: Le contraire de 1 du pt "dissociation" !!!! dans une manip particulière 5-Johnston et al. ont montrÉ que des mots identifÉs plus rapidement Étaient plus svt jugÉs comme 'old' dans une t‰che de reconnaissance que les mots identifiÉs plus lentement. Il n'est pas exclu que les phÉnomènes que l'on interprètent comme relevant de MI soient parfois de la ME involontaire cad des cas o les cues fournis dans le test conduisent ˆ un souvenir involontaire mais totalement conscient. LES INTERPRETATIONS THEORIQUES DE MI 1-Les effets de priming sur des test de MI sont attribuables ˆ l'activation temporaires de reprÉsentations ou structures de K prÉ-existantes . Cette activation est supposÉe avoir lieu de manière automatique, indÉpendamment des processus d'Élaboration nÉcessaires pour Établir de nouvelles traces Épisodiques. 2- les difÉrences entre ME et MI sont dues ˆ la nature et aux relations entre les processus d'encodage et de rÉcupÉration. Une version de cette approche est celle qui s'appuie sur la distinction entre processus dirigÉs par les donnÉes et processus dirigÉs par les concepts. Ces derniers reflètent des activitÉs initiÉes par le sjt comme l'Élaboration, l'organisation et la reconstruction, c'est sur ce type de processus que reposerait la ME alors que la MI reposerait sur des processus data-driven. 3-ME et MI renvoient ˆ des systs sous jacents diffÉrents. Pour Cohen & Squire (1984), la ME est supportÉe par une M DECLARATIVE , syst qui est en jeu dans la formation de nouvelles reprÉsentations. La MI repose sur un syst PROCEDURAL dans lequel la M se manifeste par des modifications on line de procÉdures ou opÉrations de traitement. Le syst de M Épisodique est vu comme la base pour le souvenir explicite d'evts rÉcents tandis que la M sÉmantique est responsable des perfces sur des tests de MI. Chacune de ces approches est conforme ˆ certaines des donnÉes recueillies mais pas ˆ d'autres. (shrink)

This introductory chapter attempts to clarify the philosophical, empirical, and theoretical bases on which a cognitive neuroscience approach to consciousness can be founded. We isolate three major empirical observations that any theory of consciousness should incorporate, namely (1) a considerable amount of processing is possible without consciousness, (2) attention is a prerequisite of consciousness, and (3) consciousness is required for some specific cognitive tasks, including those that require durable information maintenance, novel combinations of operations, or the spontaneous generation of intentional (...) behavior. We then propose a theoretical framework that synthesizes those facts: the hypothesis of a global neuronal workspace. This framework postulates that, at any given time, many modular cerebral networks are active in parallel and process information in an unconscious manner. An information becomes conscious, however, if the neural population that represents it is mobilized by top-down attentional amplification into a brain-scale state of coherent activity that involves many neurons distributed throughout the brain. The long-distance connectivity of these `workspace neurons' can, when they are active for a minimal duration, make the information available to a variety of processes including perceptual categorization, long-term memorization, evaluation, and intentional action. We postulate that this global availability of information through the workspace is what we subjectively experience as a conscious state. A complete theory of consciousness should explain why some cognitive and cerebral representations can be permanently or temporarily inaccessible to consciousness, what is the range of possible conscious contents, how they map onto specific cerebral circuits, and whether a generic neuronal mechanism underlies all of them. We confront the workspace model with those issues and identify novel experimental predictions. Neurophysiological, anatomical, and brain-imaging data strongly argue for a major role of prefrontal cortex, anterior cingulate, and the areas that connect to them, in creating the postulated brain-scale workspace. (shrink)

There are now various approaches to understand where and how in the brain consciousness arises from neural activity, none of which is universally accepted. Difficulties among these approaches are reviewed, and a missing ingredient is proposed here to help adjudicate between them, that of ''perspectivalness.'' In addition to a suitable temporal duration and information content of the relevant bound brain activity, this extra component is posited as being a further important ingredient for the creation of consciousness from neural activity. It (...) guides the development of what is termed the ''Central Representation,'' which is supposed to be present in all mammals and extended in humans to support self-consciousness as well as phenomenal consciousness. Experimental evidence and a theoretical framework for the existence of the central representation are presented, which relates the extra component to specific buffer working memory sites in the inferior parietal lobes, acting as attentional coordinators on the spatial maps making up the central representation. The article closes with a discussion of various open questions. (shrink)

While the study of implicit learning is nothing new, the field as a whole has come to embody — over the last decade or so — ongoing questioning about three of the most fundamental debates in the cognitive sciences: The nature of consciousness, the nature of mental representation (in particular the difficult issue of abstraction), and the role of experience in shaping the cognitive system. Our main goal in this chapter is to offer a framework that attempts to integrate current (...) thinking about these three issues in a way that specifically links consciousness with adaptation and learning. Our assumptions about this relationship are rooted in further assumptions about the nature of processing and of representation in cognitive systems. When considered together, we believe that these assumptions offer a new perspective on the relationships between conscious and unconscious processing and on the function of consciousness in cognitive systems. (shrink)