View source for Attention and consciousness

== Functional considerations == 
=== Functional role of attention === 

Complex organisms, in particular those with brains, suffer from information overload.  In primates, about one million fibers leave each eye and carry on the order of one megabyte per second of raw information. One way to deal with this deluge of data is to select a small fraction of it and to process this reduced input in real-time, while the non-selected portion of the input is processed at a reduced bandwidth. In this view, attention is a mechanism that selects information of current relevance to the organism while leaving the non-selected, and thus non-attended, data to suffer from benign neglect. 

Attentional selection is known to be based on either ‘’bottom-up/exogenous [[#Bottom-up Attention|Bottom-up Attention]]’’ or ‘’top-down/endogenous’’ factors (James, 1890; Braun and Julesz, 1998; Duncan, 1998).  However, under many conditions, subjects can disregard salient, bottom-up cues when searching for particular objects in a scene by exercising top-down, task-dependent control of their attention (Henderson et al., 2006). Bringing top-down, sustained attention to bear on an object or event in a scene takes time, however. Top-down attention selects input defined by a circumscribed region in space (focal  attention), by a particular feature (feature-based attention), or  by an object (object-based attention). It is the relationship between these volitionally-controlled forms of selective, endogenous attention and consciousness that is the topic of this entry.

=== Functional role of consciousness === 
Consciousness is surmised to have quite different functions from those of attention. These range from summarizing all relevant information pertaining to the current state of the organism and its environment and making this compact summary accessible to the planning stages of the brain, to detecting anomalies and errors, decision making, language, inferring the internal state of other animals, setting long-term goals, making recursive models, and rational thought.

To the extent that one accepts that attention and consciousness have different functions, one has to accept that they cannot be the same process.

Consider the four different ways in which a particular percept or behavior can be classified depending on whether or not it requires top-down attention and whether or not it necessarily gives rise to consciousness.