Purely parallel neural networks can model object recognition in brief displays – the same conditions under which illusory conjunctions (the incorrect combination of features into perceived objects in a stimulus array) have been demonstrated empirically (Treisman 1986; Treisman & Gelade 1980). Correcting errors of illusory conjunction is the “tag-assignment” problem for a purely parallel processor: the problem of assigning a spatial tag to nonspatial features, feature combinations, and objects. This problem must be solved to model human object recognition over a (...) longer time scale. Our model simulates both the parallel processes that may underlie illusory conjunctions and the serial processes that may solve the tag-assignment problem in normal perception. One component of the model extracts pooled features and another provides attentional tags that correct illusory conjunctions. Our approach addresses two questions: (i) How can objects be identified from simultaneously attended features in a parallel, distributed representation? (ii) How can the spatial selectional requirements of such an attentional process be met by a separation of pathways for spatial and nonspatial processing? Our analysis of these questions yields a neurally plausible simulation of tag assignment based on synchronizing feature processing activity in a spatial focus of attention. (shrink)

The general problem of visual search can be shown to be computationally intractable in a formal, complexity-theoretic sense, yet visual search is extensively involved in everyday perception, and biological systems manage to perform it remarkably well. Complexity level analysis may resolve this contradiction. Visual search can be reshaped into tractability through approximations and by optimizing the resources devoted to visual processing. Architectural constraints can be derived using the minimum cost principle to rule out a large class of potential solutions. The (...) evidence speaks strongly against bottom-up approaches to vision. In particular, the constraints suggest an attentional mechanism that exploits knowledge of the specific problem being solved. This analysis of visual search performance in terms of attentional influences on visual information processing and complexity satisfaction allows a large body of neurophysiological and psychological evidence to be tied together. (shrink)

This paper puts forward a general framework for thought about human information processing. It is intended to avoid some of the problems of pipeline or stage models of function. At the same time it avoids the snare of supposing a welter of indefinitely many separate processes. The approach is not particularly original, but rather represents the common elements or presuppositions in a number of modern theories. These presuppositions are not usually explicit, however, and making them so reduces the danger of (...) slipping back into earlier modes of thought.The key point is to distinguish between persisting representations and the processes that translate one representation into another. Various classes or groups of persisting representations can be distinguished by the experimental treatments that interfere with them. In particular, there now seem to be several kinds of short-term or temporary storage, different from each other as well as from longterm memory; the translating processes also have several different modes or kinds. A particularly important aspect of the current position is that a model of this general type no longer requires some external agent to direct and control long sequences of behaviour. (shrink)

A prominent but poorly understood domain of human agency is mental action, i.e., thecapacity for reaching specific desirable mental statesthrough an appropriate monitoring of one's own mentalprocesses. The present paper aims to define mentalacts, and to defend their explanatory role againsttwo objections. One is Gilbert Ryle's contention thatpostulating mental acts leads to an infinite regress.The other is a different although related difficulty,here called the access puzzle: How can the mindalready know how to act in order to reach somepredefined result? A (...) crucial element in the solutionof these puzzles consists in making explicit thecontingency between mental acts and mentaloperations, parallel to the contingency betweenphysical acts and bodily movements. The paper finallydiscusses the kind of reflexivity at stake in mentalacts; it is shown that the capacity to refer tooneself is not a necessary condition of the successfulexecution of mental acts. (shrink)

Philosophical considerations as well as several recent studies from neurophysiology, neuropsychology, and psychophysics converged in showing that the peripersonal space is structured in a body-centred manner and represented through integrated sensory inputs. Multisensory representations may deserve the function of coding peripersonal space for avoiding or interacting with objects. Neuropsychological evidence is reviewed for dynamic interactions between space representations and action execution, as revealed by the behavioural effects that the use of a tool, as a physical extension of the reachable space, (...) produces on visual–tactile extinction. In particular, tool-use transiently modifies action space representation in a functionally effective way. The possibility is discussed that the investigation of multisensory space representations for action provides an empirical way to consider in its specificity pre-reflexive self-consciousness by considering the intertwining of self-relatedness and object-directness of spatial experience shaped by multisensory and sensorimotor integrations. (shrink)

The effect of attention on perceived brightness and contrast was investigated in eight experiments. Attention was manipulated by engaging observers in an attention-demanding concurrent task or by directing attention to a location with a peripheral cue. In all of the dual-task manipulations, attention reduced the variability of responses. However, attention did not affect the brightness of stimuli, nor did it affect the amount of simultaneous brightness contrast. Results with peripheral location cues were similar; however, the effect of attention in these (...) experiments could be attributed to nonperceptual factors. The metaphorical “spotlight” of attention reduces observers' uncertainty about the brightness of a stimulus, but it does not “illuminate” in terms of brightness or contrast. (shrink)

Comics are complex multimodal documents that make for intriguing materials to analyze with computer vision and computational linguistics. This review summarizes the growing developments in computational modeling which have been progressing to analyze visual narratives across their various substructures.

When humans are required to perform two or more tasks concurrently, their performance declines as the tasks get closer together in time. Here, we investigated the mechanisms of this cognitive performance decline using a dual-task paradigm in a simulated driving environment, and using drift-diffusion modeling, examined if the two tasks are processed in a serial or a parallel manner. Participants performed a lane change task, along with an image discrimination task. We systematically varied the time difference between the onset of (...) the two tasks and measured its effect on the amount of dual-task interference. Results showed that the reaction times of the two tasks in the dual-task condition were higher than those in the single-task condition. SOA influenced the RTs of both tasks when they were presented second and the RTs of the image discrimination task when it was presented first. Results of drift-diffusion modeling indicated that dual-task performance affects both the rate of evidence accumulation and the delays outside the evidence accumulation period. These results suggest that a hybrid model containing features of both parallel and serial processing best accounts for the results. Next, manipulating the predictability of the order of the two tasks, we showed that in unpredictable conditions, the order of the response to the two tasks changes, causing attenuation in the effect of SOA. Together, our findings suggest higher-level executive functions are involved in managing the resources and controlling the processing of the tasks during dual-task performance in naturalistic settings. (shrink)

By reviewing most of the neurobiology of consciousness, this article highlights some major reasons why a successful emulation of the dynamics of human consciousness by artificial intelligence is unlikely. The analysis provided leads to conclude that human consciousness is epigenetically determined and experience and context-dependent at the individual level. It is subject to changes in time that are essentially unpredictable. If cracking the code to human consciousness were possible, the result would most likely have to consist of a temporal pattern (...) code simulating long-distance signal reverberation and de-correlation of all spatial signal contents from temporal signals. In the light of the massive evidence for complex interactions between implicit (non-conscious) and explicit (conscious) contents of representation, the code would have to be capable of making implicit (non-conscious) processes explicit. It would have to be capable of a progressively less and less arbitrary selection of temporal activity patterns in a continuously developing neural network structure identical to that of the human brain, from the synaptic level to that of higher cognitive functions. The code’s activation thresholds would depend on specific temporal signal coincidence probabilities, vary considerably with time and across individual experience data, and would therefore require dynamically adaptive computations capable of emulating the properties of individual human experience. No known machine or neural network learning approach has such potential. (shrink)