There are a number of meanings associated with the term such as visual attention, auditory attention, top-down and bottom-up controlled attention, and so on. In general, it refers to the selective and sustained aspects of perception that focus on certain features of the environment to the relative exclusion of other features. It may be conscious in that some stimulus elements are actively selected out of the total input, although mostly we are not explicitly aware of what leads us to perceive only some small part of the stimulus array. Models of attention often include aspects of selectivity, selecting one item in favor of another, with either the selected one being enhanced, or the other one being suppressed. Other models consider the assignment of resources to items. Another application of the term is joint attention: the process of sharing one’s experience of observing an object or event by following gaze or pointing gestures, and which is assumed to be crucial for cognitive, language and social development more generally. It is interesting to compare this outline with what William James said about attention: “Everyone knows what attention is. It is the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought. Focalization, concentration of consciousness are of its essence. It implies withdrawal from some things in order to deal effectively with others, and is a condition which has a real opposite in the confused, dazed, scatterbrained state which in French is called distraction, and Zerstreutheit in German.” (The principles of psychology, Chapter 11, p. 404). Arousal and attention are related, but in a nonlinear manner. While attentional performance improves with a moderate increase of arousal, it drops dramatically when a state of high arousal is achieved. In contrast, sustained attention reduces arousal and induces drowsiness. Furthermore, attention and arousal are based on distinct anatomical systems, mainly cortical for the former and chiefly sub-cortical for the latter. They do, however, share an anatomical substrate, namely, the thalamus. More specifically, as shown in animal research, the relay and reticular neurons in the thalamus undergo a marked alteration in discharge activity with the change from waking (viz., sustained tonic firing) to sleep onset (viz., a bursting mode). In recent years, there has been concern raised about the meaning of attention. One is that attention should not be treated as cause, but rather as an effect, and thus that theories are better regarded as those that address attentional effects as consequences.
See Arousal, Attention deficit hyperactivity disorder (ADHD), Consciousness, Controlled attention, Covert attention, Divided attention, Executive attention, Joint attention, Learning disability, Overt attention, Perception, Perception development, Pulvinar, Selective attention, Sustained attention, Thalamus