Many researchers interested in connectionist models accept that such models are "neurally inspired " but do not worry too much about whether their models are biologically realistic. While such a position may be perfectly justifiable, the present paper attempts to illustrate how biological information can be used to constrain connectionist models. Two particular areas are discussed. The first section deals with visual information processing in the primate and human visual system. It is argued that speed with which visual information is processed imposes major constraints on the architecture and operation of the visual system. In particular, it seems that a great deal of processing must depend on a single bottum-up pass. The second section deals with biological aspects of learning algorithms. It is argued that although there is good evidence for certain coactivation related synaptic modification schemes, other learning mechanisms, including back-propagation, are not currently supported by experimental data.

Efficient categorizations of complex visual stimuli require effective encodings of their distinctive properties. However, the question remains of how processes of object and scene categorization use the information associated with different perceptual spatial scales. The psychophysics of scale perception suggests that recognition uses coarse blobs before fine scale edges, because the former is perceptually available before the latter. Although possible, this perceptually determined scenario neglects the nature of the task the recognition system must solve. If different spatial scales transmit different information about the input, an identical scene might be flexibly encoded and perceived at the scale that optimizes information for the considered task—i.e., the diagnostic scale. This paper tests the hypothesis that scale diagnosticity can determine scale selection for recognition. Experiment 1 tested whether coarse and fine spatial scales were both available at the onset of scene categorization. The second experiment tested that the selection of one scale could change depending on the diagnostic information present at this scale. The third and fourth experiments investigated whether scalespecific cues were independently processed, or whether they perceptually cooperated in the recognition of the input scene. Results suggest that a mandatory low-level registration of multiple spatial scales promotes flexible scene encodings, perceptions, and categorizations.

A host of experimental data has been accumulating on the properties and mechanisms of object recognition in cortex. We review the main findings, and summarize them using a quantitative, biologically plausible, Standard Model. The model is a tool to interpret and understand the available data, and generate questions and predictions for new experiments.

This article reports a theoretical and experimental attempt to relate and contrast 2 traditionally separate research programs: inattentional blindness and attention capture. Inattentional blindness refers to failures to notice unexpected objects and events when attention is otherwise engaged. Attention capture research has traditionally used implicit indices (e.g., response times) to investigate automatic shifts of attention. Because attention capture usually measures performance whereas inattentional blindness measures awareness, the 2 fields have existed side by side with no shared theoretical framework. Here, the authors propose a theoretical unification, adapting several important effects from the attention capture literature to the context of sustained inattentional blindness. Although some stimulus properties can influence noticing of unexpected objects, the most influential factor affecting noticing is a person’s own attentional goals. The authors conclude that many—but not all—aspects of attention capture apply to inattentional blindness but that these 2 classes of phenomena remain importantly distinct.

This thesis aims to develop a psychologically plausible account of concepts by integrating key insights from philosophy (on the metaphysical basis for concept possession) and psychology (on the mechanisms underlying concept acquisition). I adopt an approach known as informational atomism, developed by Jerry Fodor. Informational atomism is the conjunction of two theses: (i) informational semantics, according to which conceptual content is constituted exhaustively by nomological mind–world relations; and (ii) conceptual atomism, according to which (lexical) concepts have no internal structure. I argue that informational semantics needs to be supplemented by allowing content-constitutive rules of inference (“meaning postulates”). This is because the content of one important class of concepts, the logical terms, is not plausibly informational. And since, it is argued, no principled distinction can be drawn between logical concepts and the rest, the problem that this raises is a general one.

We provide evidence that long-term memory encoding can occur for briefly viewed objects in a rapid serial visual presentation list, contrary to claims that the brief presentation and quick succession of objects prevents encoding by disrupting a memory consolidation process that requires hundreds of milliseconds of uninterrupted processing. Subjects performed a search task in which each item was presented for only 75 ms. Nontargets from the search task generated priming on two subsequent indirect memory tests, a search task and a task requiring identification of visually masked objects. Additional experiments revealed that information encoded into memory for these nontargets included perceptual and conceptual components, and that these results were not due to subjects maintaining items in working memory during list presentation. These results are consistent with recent neurophysiological evidence showing that stimulus processing can occur at later stages in the cognitive system even when a subsequent new stimulus is presented that initiates processing at earlier stages. It has been claimed that a process of long-term memory consolidation must be applied to perceptually encoded visual objects before a representation in memory is formed that is sufficiently stable to survive the processing of a subsequent event (Potter, 1976; Subramaniam, Biederman, & Madigan, 2000). A critical issue regarding memory consolidation is the amount of time that must be devoted to processing an event for it to be consolidated into long-term memory. Support for the conclusion that consolidation is a slow process has come from behavioral studies that used

The authors provide evidence that long-term memory encoding can occur for briefly viewed objects in a rapid serial visual presentation list, contrary to claims that the brief presentation and quick succession of objects prevent encoding by disrupting a memory consolidation process that requires hundreds of milliseconds of uninterrupted processing. Subjects performed a search task in which each item was presented for only 75 ms. Nontargets from the search task generated priming on 2 subsequent indirect memory tests: a search task and a task requiring identification of visually masked objects. Additional experiments revealed that information encoded into memory for these nontargets included perceptual and conceptual components, and that these results were not due to subjects maintaining items in working memory during list presentation. These results are consistent with recent neurophysiological evidence showing that stimulus processing can occur at later stages in the cognitive system even when a subsequent new stimulus is presented that initiates processing at earlier stages.

Numerous psychophysical experiments have shown an important role for attentional modulations in vision. Behaviorally, allocation of attention can improve performance in object detection and recognition tasks. At the neural level, attention increases firing rates of neurons in visual cortex whose preferred stimulus is currently attended to. However, it is not yet known how these two phenomena are linked, i.e., how the visual system could be “tuned ” in a task-dependent fashion to improve task performance. To answer this question, we performed simulations with the HMAX model of object recognition in cortex [45]. We modulated firing rates of model neurons in accordance with experimental results about effects of featurebased attention on single neurons and measured changes in the model’s performance in a variety of object recognition tasks. It turned out that recognition performance could only be improved under very limited circumstances and that attentional influences on the process of object recognition per se tend to display a lack of specificity or raise false alarm rates. These observations lead us to postulate a new role for the

Although existing GUIs have a sense of space, they provide no sense of place. Numerous studies report that users misplace files and have trouble wayfinding in virtual worlds despite the fact that people have remarkable visual and spatial abilities. This issue is considered in the human-computer interface field and has been addressed with alternate display/navigation schemes. Our paper presents a fundamentally graphics based approach to this `lost in hyperspace' problem. Specifically, we propose that spatial display of files is not sufficient to engage our visual skills

The Problem: Top-down attention is assumed to allow for task-specific tuning of the human and monkey visual system. While effects and mechanisms of top-down spatial attention are experimentally wellstudied and provide no particular theoretical difficulties the same is not true for mechanisms of nonspatial attention. So far studies have failed to provide conclusive evidence whether top-down tuning through non-spatial attention actually happens and, in particular, whether it can improve performance in object recognition tasks. Motivation: Two lines of research suggest that nonspatial top-down attention facilitates object recognition. In neurophysiological studies it has been shown that feature-specific attention can modulate the response of neurons (especially in V4 and IT) to visual stimuli and induce delay activity in cells selective for the attended features (stimuli) ([4, 5]). These observations are explained e.g. in terms of the biasedcompetition model. According to the model, these modulations reflect a physiological mechanism to selectively enhance the neural representation of the behaviorally relevant (i.e. attended) stimuli while suppressing representations of distractor stimuli. Psychophysical research on human performance in object recognition suggests that specific information about a stimulus, provided before the stimulus is shown, facilitates perception. In RSVP experiments subjects ’ performance increased with the precision