Influence in viewer attention

2.2 Factors Influencing Viewers Attention

The amount of visual attention captured by an object is a key factor in the determination of its relevance.

A set of factors influencing eye movements and viewer attention has been identified; they are shortly presented below grouped as low-level and high-level factors, depending on the type of semantic information addressed.

Low-level factors include the amount of motion (vision mechanisms are very sensitive to changes in motion), the position (attention is usually focused on the image center for more than 25% of time), the size, the type of shape and its orientation, the color and brightness, and also the contrast of the object to its neighbors.

High-level factors include the knowledge if an object is part of the background (as foreground objects usually get more attention), if the object is a person (as the presence of people, faces, eyes, mouth, hands usually attracts viewing attention), and also the context of viewing (as certain objects may become more relevant in some circumstances).

Besides the factors mentioned above, also object masking may affect the perception of the various image components in presence of each other and of noise. In particular, similarly textured neighboring objects may mask each other, and the existence of a gaze point towards an object may also mask the presence of other objects in an image.

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