Attention



Attention is the cognitive process of selectively concentrating on one aspect of the environment while ignoring other things. Attention has also been referred to as the allocation of processing resources.

Examples include listening carefully to what someone is saying while ignoring other conversations in a room (the cocktail party effect) or listening to a cell phone conversation while driving a car. Attention is one of the most intensely studied topics within psychology and cognitive neuroscience.

In 1890, William James, in his textbook Principles of Psychology, remarked: 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.

Attention remains a major area of investigation within education, psychology and neuroscience. Areas of active investigation involve determining the source of the signals that generate attention, the effects of these signals on the tuning properties of sensory neurons, and the relationship between attention and other cognitive processes like working memory and vigilance. A relatively new body of research is investigating the phenomenon of traumatic brain injuries and their effects on attention.

1850s to 1900s
In James' time, the method more commonly used to study attention was introspection. However, as early as 1858, Franciscus Donders used mental chronometry to study attention and it was considered a major field of intellectual inquiry by such diverse authors as Sigmund Freud. One major debate in this period was whether it was possible to attend to two things at once (split attention). Walter Benjamin described this experience as "reception in a state of distraction." This disagreement could only be resolved through experimentation.

1950s to present
In the 1950s, research psychologists renewed their interest in attention when the dominant epistemology shifted from positivism (i.e., behaviorism) to realism during what has come to be known as the "cognitive revolution". The cognitive revolution admitted unobservable cognitive processes like attention as legitimate objects of scientific study.

Modern research on attention began with the analysis of the "cocktail party problem" by Colin Cherry in 1953. At a cocktail party how do people select the conversation that they are listening to and ignore the rest? This problem is at times called "focused attention", as opposed to "divided attention". Cherry performed a number of experiments which became known as dichotic listening and were extended by Donald Broadbent and others. In a typical experiment, subjects would use a set of headphones to listen to two streams of words in different ears and selectively attend to one stream. After the task, the experimenter would question the subjects about the content of the unattended stream. Experiments by Gray and Wedderburn and later Anne Treisman pointed out various problems in Broadbent's early model and eventually led to the Deutsch-Norman model in 1968. In this model, no signal is filtered out, but all are processed to the point of activating their stored representations in memory. The point at which attention becomes "selective" is when one of the memory representations is selected for further processing. At any time, only one can be selected, resulting in the attentional bottleneck.

This debate became known as the early-selection vs late-selection models. In the early selection models (first proposed by Donald Broadbent and Anne Treisman), attention shuts down or attenuates processing in the unattended ear before the mind can analyze its semantic content. In the late selection models (first proposed by J. Anthony Deutsch and Diana Deutsch), the content in both ears is analyzed semantically, but the words in the unattended ear cannot access consciousness. This debate has still not been resolved.

Anne Treisman developed the highly influential feature integration theory. According to this model, attention binds different features of an object (e.g., color and shape) into consciously experienced wholes. Although this model has received much criticism, it is still widely cited and spawned similar theories with modification Jeremy Wolfe's Guided Search Theory.

In the 1960s, Robert Wurtz at the National Institutes of Health began recording electrical signals from the brains of macaques who were trained to perform attentional tasks. These experiments showed for the first time that there was a direct neural correlate of a mental process (namely, enhanced firing in the superior colliculus).

In the 1990s, psychologists began using PET and later fMRI to image the brain in attentive tasks. Because of the highly expensive equipment that was generally only available in hospitals, psychologists sought for cooperation with neurologists. Pioneers of brain imaging studies of selective attention are psychologist Michael I. Posner (then already renowned for his seminal work on visual selective attention) and neurologist Marcus Raichle. Their results soon sparked interest from the entire neuroscience community in these psychological studies, which had until then focused on monkey brains. With the development of these technological innovations neuroscientists became interested in this type of research that combines sophisticated experimental paradigms from cognitive psychology with these new brain imaging techniques. Although the older technique of EEG had long been used to study the brain activity underlying selective attention by cognitive psychophysiologists, the ability of the newer techniques to actually measure precisely localized activity inside the brain generated renewed interest by a wider community of researchers. The results of these experiments have shown a broad agreement with the psychological, psychophysiological and the experiments performed on monkeys.

In Humans
Selective attention is the focusing of one’s conscious awareness on a particular stimulus. The senses take in billions of bits of information every second, but only about 40 are processed by the brain. One example of selective attention is the “Cocktail Party Effect” where a person is able to focus on a certain voice in a noisy room. Selective attention is also a factor in car accidents, drivers focusing on talking on a phone or holding a conversation with a passenger are more likely to be in an accident because they are more focused on the conversation than on the driving.

The inability of children to resolve conflict is generally because they lack executive control of their attention. Executive function is developed in early childhood and becomes useful to adults when resolving conflicts and planning new actions. It is developed differently among individuals and this natural development is one reason why people differ in their behavior as well as their emotional control. The ability to resolve conflicts is minimal as an infant, for example, an infant’s ability to reach for a toy differs at ages 9 months and 1 year. Context sensitive learning of sequences is a form of learning which allows adults to acquire higher level attention than children, and therefore resolve larger conflicts. The capability to learn this way begins at around 18 months and is practiced throughout the life span. Studies suggest that executive attention goes through the most dramatic change at 3 years of age.

Influence of Processing Load
One theory regarding selective attention is the load theory, which states that there are two mechanisms that affect attention: cognitive and perceptual. The perceptual considers the subject’s ability to perceive or ignore stimuli, both task-related and non task-related. Studies show that if there are many stimuli present (especially if they are task-related), it is much easier to ignore the non-task related stimuli, but if there are few stimuli the mind will perceive the irrelevant stimuli as well as the relevant. The cognitive refers to the actual processing of the stimuli, studies regarding this showed that the ability to process stimuli decreased with age, meaning that younger people were able to perceive more stimuli and fully process them, but were likely to process both relevant and irrelevant information, while older people could process fewer stimuli, but usually processed only relevant information.

Some people can process multiple stimuli, e.g. trained morse code operators have been able to copy 100% of a message while carrying on a meaningful conversation. This relies on the reflexive response due to "overlearning" the skill of morse code reception/detection/transcription so that it is an autonomous function requiring no specific attention to perform.

In Other Animals
Ecological research in the past few decades has shown that most animals acquire and respond adaptively to information that affects survival and reproduction. At the same time, neurobiological studies have established that the rate of information processing by the brain is much lower than the rate at which information is encountered in the environment, and that attentional mechanisms enable the brain to focus only on the most essential information at any given time. Current data indicate that limited attention affects diet choice and constrains animals' ability simultaneously to feed and attend to predators.

Selective visual attention
In cognitive psychology there are at least two models which describe how visual attention operates. These models may be considered loosely as metaphors which are used to describe internal processes and to generate hypotheses that are falsifiable. Generally speaking, visual attention is thought to operate as a two-stage process. In the first stage, attention is distributed uniformly over the external visual scene and processing of information is performed in parallel. In the second stage, attention is concentrated to a specific area of the visual scene (i.e. it is focused), and processing is performed in a serial fashion.

The first of these models to appear in the literature is the spotlight model. The term "spotlight" was first used by David LaBerge, and was inspired by the work of William James who described attention as having a focus, a margin, and a fringe. The focus is an area that extracts information from the visual scene with a high-resolution, the geometric center of which being where visual attention is directed. Surrounding the focus is the fringe of attention which extracts information in a much more crude fashion (i.e. low-resolution). This fringe extends out to a specified area and this cut-off is called the margin.

The second model is called the zoom-lens model, and was first introduced in 1983. This model inherits all properties of the spotlight model (i.e. the focus, the fringe, and the margin) but has the added property of changing in size. This size-change mechanism was inspired by the zoom lens you might find on a camera, and any change in size can be described by a trade-off in the efficiency of processing. The zoom-lens of attention can be described in terms of an inverse trade-off between the size of focus and the efficiency of processing: because attentional resources are assumed to be fixed, then it follows that the larger the focus is, the slower processing will be of that region of the visual scene since this fixed resource will be distributed over a larger area. It is thought that the focus of attention can subtend a minimum of 1° of visual angle, however the maximum size has not yet been determined.

Attention Researchers have described two different ways in which our minds select items present in the environment to attend to. The first method gathers data through the senses and the second, through interacting with preexisting information that has been stored in memory.

The first method is called Bottom-Up processing and it is a stimulus driven mechanism which focuses on salient changes in the environment to capture attention. For example, a person is walking down a busy street and an ambulance drives by, immediately catching their attention. Despite the sounds, sights and smells that exist on that busy street, it is the ambulance which automatically captures the person's attention.

The second method is called Top-Down processing which is when one strategically directs their attention to current goals and expectations due to past experience. This is done through memory. An example of this is when you repeatedly place an item in the same spot and this causes you to direct your attention to that spot when it comes time to retrieve that specific item. Using a wallet as the example, one may place it on their dresser each night when they return home from work. The next day, as they head out the door, they are able to redirect their attention to where the wallet is (on the dresser) instead of having to search the entire house for it.

Overt and covert attention
Attention may be differentiated according to its status as "overt" versus "covert". Overt attention is the act of directing sense organs towards a stimulus source. Covert attention is the act of mentally focusing on one of several possible sensory stimuli. Covert attention is thought to be a neural process that enhances the signal from a particular part of the sensory panorama.

There are studies that suggest the mechanisms of overt and covert attention may not be as separate as previously believed. Though humans and primates can look in one direction but attend in another, there may be an underlying neural circuitry that links shifts in covert attention to plans to shift gaze. For example, if individuals attend to the right hand corner field of view, movement of the eyes in that direction may have to be actively suppressed.

The current view is that visual covert attention is a mechanism for quickly scanning the field of view for interesting locations. This shift in covert attention is linked to eye movement circuitry that sets up a slower saccade to that location.

Clinical model of attention
Attention is best described as the sustained focus of cognitive resources on information while filtering or ignoring extraneous information. Attention is a very basic function that often is a precursor to all other neurological/cognitive functions. As is frequently the case, clinical models of attention differ from investigation models. One of the most used models for the evaluation of attention in patients with very different neurologic pathologies is the model of Sohlberg and Mateer. This hierarchic model is based in the recovering of attention processes of brain damage patients after coma. Five different kinds of activities of growing difficulty are described in the model; connecting with the activities that patients could do as their recovering process advanced.
 * Focused attention: The ability to respond discretely to specific visual, auditory or tactile stimuli.
 * Sustained attention (vigilance): The ability to maintain a consistent behavioral response during continuous and repetitive activity.
 * Selective attention: The ability to maintain a behavioral or cognitive set in the face of distracting or competing stimuli. Therefore it incorporates the notion of "freedom from distractibility."
 * Alternating attention: The ability of mental flexibility that allows individuals to shift their focus of attention and move between tasks having different cognitive requirements.
 * Divided attention: This is the highest level of attention and it refers to the ability to respond simultaneously to multiple tasks or multiple task demands.

This model has been shown to be very useful in evaluating attention in very different pathologies, correlates strongly with daily difficulties and is especially helpful in designing stimulation programs such as APT (attention process training), a rehabilitation program for neurologic patients of the same authors.

Executive attention
Inevitably situations arise where it is advantageous to have cognition independent of incoming sensory data or motor responses. There is a general consensus in psychology that there is an executive system based in the frontal cortex that controls our thoughts and actions to produce coherent behavior. This function is often referred to as executive function, executive attention, or cognitive control.

No exact definition has been agreed upon. However, typical descriptions involve maintaining behavioral goals, and using these goals as a basis for choosing what aspects of the environment to attend to and which action to select.

Neural correlates of attention
Most experiments show that one neural correlate of attention is enhanced firing. If a neuron has a certain response to a stimulus when the animal is not attending to the stimulus, then when the animal does attend to the stimulus, the neuron's response will be enhanced even if the physical characteristics of the stimulus remain the same.

In a recent review, Knudsen describes a more general model which identifies four core processes of attention, with working memory at the center:
 * Working memory temporarily stores information for detailed analysis.
 * Competitive selection is the process that determines which information gains access to working memory.
 * Through top-down sensitivity control, higher cognitive processes can regulate signal intensity in information channels that compete for access to working memory, and thus give them an advantage in the process of competitive selection. Through top-down sensitivity control, the momentary content of working memory can influence the selection of new information, and thus mediate voluntary control of attention in a recurrent loop (endogenous attention).
 * Bottom-up saliency filters automatically enhance the response to infrequent stimuli, or stimuli of instinctive or learned biological relevance (exogenous attention ).

Neurally, at different hierarchical levels spatial maps can enhance or inhibit activity in sensory areas, and induce orienting behaviors like eye movement.
 * At the top of the hierarchy, the frontal eye fields (FEF) on the dorsolateral frontal cortex contain a retinocentric spatial map. Microstimulation in the FEF induces monkeys to make a saccade to the relevant location. Stimulation at levels too low to induce a saccade will nonetheless enhance cortical responses to stimuli located in the relevant area.
 * At the next lower level, a variety of spatial maps are found in the parietal cortex. In particular, the lateral intraparietal area (LIP) contains a saliency map and is interconnected both with the FEF and with sensory areas.
 * Certain automatic responses that influence attention, like orienting to a highly salient stimulus, are mediated subcortically by the superior colliculi.
 * At the neural network level, it is thought that processes like lateral inhibition mediate the process of competitive selection.

In many cases attention produces changes in the EEG. Many animals, including humans, produce gamma waves (40–60 Hz) when focusing attention on a particular object or activity.