229,021 research outputs found
A normalization model of visual search predicts single trial human fixations in an object search task
When searching for an object in a scene, how does the brain decide where to
look next? Theories of visual search suggest the existence of a global
attentional map, computed by integrating bottom-up visual information with
top-down, target-specific signals. Where, when and how this integration is
performed remains unclear. Here we describe a simple mechanistic model of
visual search that is consistent with neurophysiological and neuroanatomical
constraints, can localize target objects in complex scenes, and predicts
single-trial human behavior in a search task among complex objects. This model
posits that target-specific modulation is applied at every point of a
retinotopic area selective for complex visual features and implements local
normalization through divisive inhibition. The combination of multiplicative
modulation and divisive normalization creates an attentional map in which
aggregate activity at any location tracks the correlation between input and
target features, with relative and controllable independence from bottom-up
saliency. We first show that this model can localize objects in both composite
images and natural scenes and demonstrate the importance of normalization for
successful search. We next show that this model can predict human fixations on
single trials, including error and target-absent trials. We argue that this
simple model captures non-trivial properties of the attentional system that
guides visual search in humans.Comment: 8 figure
Strictification of etale stacky Lie groups
We define stacky Lie groups to be group objects in the 2-category of
differentiable stacks. We show that every connected and etale stacky Lie group
is equivalent to a crossed module of the form (H,G) where H is the fundamental
group of the given stacky Lie group and G is the connected and simply connected
Lie group integrating the Lie algebra of the stacky group. Our result is
closely related to a strictification result of Baez and Lauda.Comment: 25 page
Semantic categories underlying the meaning of ‘place’
This paper analyses the semantics of natural language expressions that are associated with the intuitive notion of ‘place’. We note that the nature of such terms is highly contested, and suggest that this arises from two main considerations: 1) there are a number of logically
distinct categories of place expression, which are not always clearly distinguished in discourse about ‘place’; 2) the many non-substantive place count nouns (such as ‘place’, ‘region’, ‘area’, etc.) employed in natural
language are highly ambiguous. With respect to consideration 1), we propose that place-related expressions
should be classified into the following distinct logical types: a) ‘place-like’ count nouns (further subdivided into abstract, spatial and substantive varieties), b) proper names of ‘place-like’ objects, c) locative property phrases, and d) definite descriptions of ‘place-like’ objects. We outline possible formal representations for each of these. To address consideration 2), we examine meanings, connotations and ambiguities of the English vocabulary of abstract and generic place count nouns, and identify underlying elements of meaning, which explain both
similarities and differences in the sense and usage of the various terms
Designing Sugaropolis:digital games as a medium for conveying transnational narratives
In this paper, the authors present a case study of ‘Sugaropolis’: a two-year practice-based project that involved interdisciplinary co-design and stakeholder evaluation of two digital game prototypes. Drawing on the diverse expertise of the research team (game design and development, human geography, and transnational narratives), the paper aims to contribute to debates about the use of digital games as a medium for representing the past. With an emphasis on design-as-research, we consider how digital games can be (co-)designed to communicate complex histories and geographies in which people, objects, and resources are connected through space and time
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