Selective Visual Attention: Computational Models and Applications

1.2 Types of Selective Visual Attention

In Section 1.1 we showed that visual attention is an ability of humans and quadrumanes, and exists universally. Over the past several decades, many researchers, especially physiologists, psychologists and computational neuroscientists, have tried to understand the mechanisms of visual attention. Different types of selective visual attention has been explored and described in the literature from different viewpoints and with different emphases, such as pre-attention and attention [25, 26], bottom-up attention and top-down attention, voluntary and passive attention, parallel and serial processing of attention in the brain, overt and covert attention and so on. Although these types are related, overlapped or similar, it is beneficial to discuss them for the purpose of understanding of visual attention studies and the related theory, since in fact, the different types (to be introduced in the rest of this section) reflect different aspects of selective visual attention and are often complementary to each other.

1.2.1 Pre-attention and Attention

From the signal processing point of view, visual attention is divided into two stages: pre-attention and attention stages, as proposed by Neisser and Hoffman [25, 26]. The pre-attention stage provides the necessary information for attention processing. For instance, a single feature such as orientation, colour or motion must be detected before the stimulus can be selected for further processing. In this ...