1. About Behaviour

Understanding and interpreting behaviours of objects, and in particular those of humans, is central to social interaction and communication. In particular, visual behaviour refers to the actions or reactions of a sensory mechanism in response to a visual stimulus, for example, the navigation mechanism of nocturnal bees in dim light, visual search by eye movement of infants or drivers in response to their surrounding environment. If visual behaviour as a search mechanism is a perceptual function that scans actively a visual environment in order to focus attention and seek an object of interest among distracters, visual analysis of behaviour is a perceptual task that interprets actions and reactions of objects, such as people, interacting or co-existing with other objects in a visual environment. Recognising objects visually by behaviour and activity rather than shape and size is important to the human visual system. Since 1970s, the computer vision community has endeavoured to bring about intelligent perceptual capabilities to artificial visual sensors. This endeavour has been intensified in recent years by the need for understanding massive quantity of video data, with the aim to not only comprehend objects spatially in a snapshot but also their spatiotemporal relations over time in a sequence of images. In this chapter, we introduce the computational study of visual analysis of behaviour, in particular of human behaviour, and outline the opportunities and challenges for visual analysis of behaviour.