Bottom-Up Attention, Models of

Abstract

DefinitionAttention -a general concept covering all factors that influence selection mechanisms, whether they are scene-driven and bottom-up, or expectation-driven and top-down.Salience -parts of a stimulus (e.g. image, video, audio) that appear to an observer to stand out, relative to their neighboring parts. It is a subjective perceptual quality.Gaze -a coordinated motion of the eyes and the head that is long enough to concentrate on something. It is a key property of attention in natural behavior.Scene free-viewing -A task in which participants are asked to look at an image, without any specific instruction. As a default scene analysis task, the free viewing paradigm offers a wealth of insights regarding the cues that attract attention. Detailed Description History, scope, and organizationDeciphering the computational mechanisms by which the brain deals with the computational complexity of an overwhelmingly high volume of incoming data (at a rate of 10 8 bits/s [46]) and how the brain programs eye movements continue to be important problems in neuroscience. Where humans look in images and videos provides important clues regarding how they perceive static (still images) and dynamic scenes (videos), locate the main focus of the image, recognize actions or events, and identify the main participants.A significant amount of behavioral and computational research on attention has revealed that attention is deployed in two ways: bottom-up (BU) and top-down (TD). The bottom-up component of attention, a.k.a endogenous or stimulus-driven, processes sensory information primarily in a feed-forward manner. Typically, a series of successive transformations are applied to the input visual signal to highlight the most interesting, important, conspicuous, or so-called salient regions [45,36]. In contrast, in top-down attention, a.k.a context-driven, or goal-driven, information related to the ongoing behavior, task, or goal is selected (e.g. staying within the road lanes while driving [52]). The reader is referred to [51,2,27,57,11] for reviews of top-down attention studies. Please see also the chapter on top-down attention in this encyclopedia [66].Conventionally, bottom-up attention models generate a 2D topographic saliency map, where a value at every location determines how salient that location is, relative to its neighbors. The goal in saliency *