Thursday, December 29, 2011

Attention and Executive Attention

Attention refers to selecting certain information from among many and focusing mental resources on those selected. Our sensory systems are continually bombarded by sights, sounds, smells and other signals from outside world. At the same time, we remember events that just occurred seconds ago and events from distant past. Along with these memories there are mental pictures of events only imagined to occur in the present or in future.
From moment to moment only one stream of thought is kept in the focus of consciousness to the exclusion of others. Only one internal or external event dominates consciousness, and others are barely noticed or not noticed at all. This process of selection of information at mental level is called attention. The mental faculty of attention allows us to focus on what is important at the moment and to ignore the rest. If our attention fails we are perplexed by a plethora of information and become unable to function.
Consider some everyday situations in which attention is important. When you carry on a conversation with someone, there are numerous irrelevant background stimuli. The sights and sounds of a nearby television, the distant roar of a flying jet, the songs of birds outside the window, the pressure of clothing on the skin, and the pain of recently injured finger all compete for your attention. In conversations, it is further necessary to divide attention or shift attention from listening, on the one hand, to speaking on the other.
Now, consider carrying on your conversation on a cell phone while driving a car. It is necessary to ignore some distractions, such as the car radio and the sounds of traffic in order to focus on the speech production and comprehension. At the same time the task of driving also demands attention. Perception of road, other cars and pedestrians is essential for driving. Steering and braking also demand attention, particularly when traffic is heavy. Thus, to drive a car and carry on a telephone conversation at the same time requires that attention be divided among multiple tasks, each of which can be highly demanding at a given moment in time. Not surprisingly, inattention is a leading cause of traffic accidents. Therefore prohibition by law, of cell phone talks while driving is essential to reduce the number of traffic accidents.
Selective attention
Theories on attention are divided into two groups. The first group, called filter theories, assumes that attention operates as a filter that blocks the processing of some stimuli and allows the processing of others. In other words attention is selective. The filter theories were designed to explain how selective attention operates.  Selective attention may result from filtering of the unattended channel. Another possibility is that the unattended information is attenuated rather than filtered entirely.  
Divided attention
The second group of theories assumes that the person actively chooses stimuli for further processing by allocating a portion on or more limited pools of attentional capacity. These theories are called capacity theories. The capacity theories address the question how the mind concentrates on a particular stimulus. Here the attention is conceived as a mental effort. The more a task requires of a limited pool of available capacity, the more mental effort the person exerts. For example, try to solve these two arithmetic problems in mind:
(a) 6 x 6 =?
    (b) 32 x 16 =?
Clearly, problem b demands more mental effort.  
Experiment to prove this theory: While a person solves a series of either easy or hard multiplication problems presented over headphones, the person is given a secondary task of detecting the random appearance of a light on a panel in front. The instruction given to the person is to concentrate on the multiplication tasks. He has to press a button each time when the light appears. It was proved that while the person was solving the harder problems he did not press the button, showing that he could not attend to the light appeared in the panel on the front.
Automatic processes
John Ridley Stroop in 1935 devised an ingenious test to study automatic reading. While reading the words in different colours shown in the picture, colour terms occur automatically and effortlessly. The colour terms (e.g. RED, YELLOW, BLUE, GREEN, and RED) are printed in incompatible colours. For example the first word BLACK appears in red colour and so on. The task is to say aloud the colour of the ink while ignoring the meaning of the word itself. While doing it the word recognition, one aspect of fluent reading, occurs automatically. It is exceedingly difficult to ignore the meaning of the word BLACK when it appears in red colour. The correct response “red” competes with the habitual response of the word black. Errors and delays in responding of the word BLACK when it appears in red are the usual result. This is called Stroop effect.
Word recognition illustrates one of many processes that have become automatic because of extensive practice, maturation and skill development. Walking, running, riding a bicycle and typing on a key board are among the many motor skills that people automatize. Many mental skills also become automatic and are carried out effortlessly. Automatic process occurs unintentionally, unconsciously and operates without depleting attentional capacity. Put differently, automatic processes are often called preattentive.  On the other hand controlled processes are intentional, conscious and demanding of attention.
Practice and Automaticity
A process or a set of processes used in a particular skill, such as typing, becomes automatic only after extensive practice. Certain processes may be so basic for human learning and survival that they are genetically programmed to operate through maturation and interaction with environment. Motor skill exemplifies processes that achieve automaticity through genetic programming in addition to practice. Learning to crawl, walk and run is not simply a matter of practice. At birth there is a reflex to move the arms and legs in a crawling movement. This reflex disappears after about three months. Some species are programmed to walk moments after birth to ensure their survival. Humans adopt a more leisurely pace with the infant wholly dependent on the mother and father for survival. The effortlessness and automaticity that we see in the motor skill of an older child running while at play is only partly due to practice.
Basic mental processes may also be genetically programmed or hard wired in the nervous system. These should appear early in development and acquire relatively little learning to become fully operational. Age, culture, intelligence, educational attainment and other factors that strongly influence consciously controlled processes are unimportant for innate automatic processes.
Executive attention
This refers to a supervisory attentional system that inhibits inappropriate responses and activates appropriate ones.  Its function is to control our thoughts and behaviours in adaptive ways. Imagine leaving a parking lot to drive home in the evening. If your usual routine is to drive straight home, then executive attention is needed to intervene and activate the thought of going first to, say, a grocery store . The automatic response of driving home must be inhibited or else it will control behaviour. Executive attention is always needed when (i) planning or making decisions, (ii) correcting errors, (iii) the required response is novel or not well-learned; (iv) conditions are dangerous.
MRI Picture of anterior cingulate gyrus
The Stroop task described above is an excellent example where active executive attention is required to give correct responses. Brain imaging studies conducted during the Stroop task test have established that the anterior part of the cingulated gyrus, a region in the frontal lobe of the brain is the location of executive attentional system, inhibiting the automatic response and selecting the correct response.

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