Attention is one of the most important aspects of sensory mechanisms, including vision.
The most recent studies show how the degree of attention marks to a great extent the level of vision, we could say that we see what we look at, what we pay attention to, that is why we are going to give a base on the most relevant of the attention for that we can better understand the mechanism of vision.
What is the vision and attention
In the literature we can find multiple definitions of attention, highlighting a common fact, "although we all know what attention is, there is no clear description of it". Posner and Boeis (1971) proposed that attention has three characteristic components: orientation to sensory events, detection of signals for focused processing, and maintenance of a state of wakefulness or alertness.
It seems that there is some agreement that the attention involves selecting certain information to process it carefully and prevent other information from overlapping, continue processing. Another way of understanding attention is to find out what happens when it fails. There are two types of fundamental failures, selection failures in space and selection failures in time.
Selection failures in space occur when we are presented with a lot of information at the same time, like when we are at a party with a lot of people, it is impossible to attend to everything that happens. It usually happens that if we are attending to something concrete, there are aspects of the scene that surrounds our point of attention, which will go unnoticed by us, even if significant changes occur that fall within our campor vision. If we attend to something concrete, our campor perceptive is reduced considerably, it is what is called blindness for change (very used by magicians and illusionists).
We also know that top-down mechanisms they can condition our attentive system. If we are hungry, we are more likely to detect a fruit basket than when we have finished eating. We see, we perceive, according to mixed mechanisms from top to bottom and bottom to top, modulated by attention.
Selective and divided attention
When we focus on a certain task and only on that, it is what we call selective attention, whereas when we have to attend to more than one thing, we talk about divided attention. It is important to know that in divided attention information will be lost because there is always a rivalry between the incoming information of one task and another, predominating the one with the strongest inputs.
Speed in information processing
Just as there are limitations on the amount of information that can be processed simultaneously in space, there are also limitations on the speed with which that information is processed in a time sequence.
With experimental studies it was found that if we are paying attention to something and we want to change to pay attention to something else, a time lapse must occur, a lapse that is known as “attention flicker”, a short-lived window during which afferent information is not registered, similar to the absence of visual information when we blink, hence its name. Attention to the first object precludes detection of the second.
The attention failure
One of the most studied topics is related to the search for the motive of attention failure, spatial or temporal.
A first explanation would be in the fact that there was a limitation at the sensory level, in the receiving organs. We do not get more information because our visual system can not collect more data, it is saturated. Everything indicates that it is true that the visual system has limitations in the amount of information it can process, but this limitation would only partly explain attentional failures.
We know that the visual system processes an object or image each time, sequentially, so in the bottom sheets figure, although the change is very fast, we can only attend to one option, or the background or the figure, but never both simultaneously. In the example of the cup-face, we see either the cup or the face, but not both simultaneously and does not go through a problem of saturation of the sensory organ.
Vision and hearing
If we propose the arrival of simultaneous information using two different sensory organs, vision and hearing, there is also an interference in the capture and processing of information, although less than the interference that is recorded when different information is sent on the same sensory channel.
All this led to think that the attentional failures, the limitations, although there would be a certain degree related to the sensory organ, the main cause was not this, but some problem at a more internal brain level.
Hemispatial negligence
Analyzing cases of hemispatial neglect, it was observed that in most of these patients there had been damage to the right parietal lobe, they did not process information that fell into the area of the campor visual left, although the visual system was correct, there was no alteration in the retina or in the optical path that will explain these omissions.
This situation not only occurred in direct perception, when we look at something, but also when we imagine something, when we remember with mental images, the omission of part of the information from the contralateral zone to the location of the lesion continues to occur.
Search and selection of objects with vision
The search and detection of something, objects, faces, etc., can follow a top-down or inverse process.
Endogenous care
In the first case, we seek, we select voluntarily, we know what we are looking for, it is a process that comes from within, that is why it is called endogenous care. It is a directed search and, although it can be useful in many circumstances, it has one drawback, that of hiding important stimuli from the external environment that we do not pay attention to and go unnoticed, slowing down the selection process.
Exogenous care
Similarly, when we are looking for something, even if it is voluntary, that is, knowing what we are looking for, the presence of an external bland stimulus (a bright light), even though it has no relation to what we are looking for, can distract us, capture our attention diverting it from the main search objective. A necessary condition for the "distraction" is that the external stimulus is powerful enough to divert our attention. This mechanism of attentional change by external stimuli is what is known as exogenous care.
Differences between endogenous and exogenous care
Endogenous attention requires more time in the processing of information, while exogenous stimuli usually capture our attention almost automatically, with less time, since they do not require cognitive processing to "understand" that stimulus, which is what we call " Pop out. " When we look for a glass of water in the kitchen, if there is a powerful flash of light, our eyes will go to the area where that flash occurred, without needing to think anything else, automatically. In experiments with facilitation signals, we know that these help in the detection of objects, provided that the object is shown after a minimum period of 150 msg between both, time necessary for the information to be processed cognitively.
When we direct our attention to a single object, the ability to perceive and remember its characteristics is much higher than when we have our attention divided into two objects or when we are performing two tasks at the same time. In the focused or selective attention on a single object, it has been seen that we can simultaneously attend to different parts of that object.
In a study where a house was projected with a superimposed semi-transparent face, it was observed by means of neuroimages with fMRI, which simultaneously stimulated the occipital areas corresponding to the vision of the house and the temporal zone corresponding to the specific processing of the faces.
Processing of information
Attention requires a process of information selection, we capture some stimuli and discard others, among other things because we are unable to process all the information that comes to us.
A frequent question among researchers is when the selection occurs, at the beginning of the arrival and processing of the information or at later stages. The question focuses on where the bottleneck is located. For Broadbent, 1958, the selection is given in the initial phases. The information that arrives would pass through a brief sensitive storage in which the physical characteristics of the input are analyzed. In the vision, these characteristics would be movement, color, form, location. The bottleneck would be located after this sensitive storage, so that only a small part of the information would go to a higher level, for an additional semantic processing. This idea was confirmed with the experiences of Cherry (1953) with dichotic listening but, although this model allowed to explain much of what was happening, it left some questions unresolved.
Another interpretation that has been made of attention is what is called "Theory of the light bulb" Just as a light bulb illuminates an area and highlights the information that is illuminated, making the information that is outside the illuminated area less noticeable, the attention would work in a similar way, as a light source that allows information to be captured within a circumscribed area. This hypothesis has been recently refuted with multiple experimental works.
As a result of these experiences that resolve only in part the questions about care, authors have emerged who propose understand attention as a dynamic system, in which we are able to select certain information while automatically and actively inhibiting other information. We would understand attention as a competitive system of selection and inhibition.
Theory of the integration of characteristics
Perhaps the most accepted theory of attention at the present time is the one proposed by Treisman and Gelade in 1980, the Theory of the integration of ICT characteristics (see Figure).
The theory of the integration of characteristics defends that when we see an image, maps of independent characters are produced, the one of forms, the one of colors, etc, so that each map contains partial information of the scene. In a later phase they merge and we have a unique map of the whole scene. The attention consists in grouping and, especially, comparing these maps, to be able to see the differences or particular characteristics of each map and thus to have information of the details of that scene. The comparative analysis of maps makes the detection of details faster, something that would be in line with the experimental studies. It also explains the errors that occur when you confuse details when the amount of information is large.
In this way, attention is no longer considered as a simple bottleneck but as a selective distribution of a limited amount of cognitive resources. It would be a "modulator" that increases or decreases the efficiency with which a sensory process is performed.
In studies with functional magnetic resonance we can see how different brain areas participate, from the occipital lobes to the frontal and prefrontal areas of decision making. It is an input competition, as suggested by Duncan (1997). The input that receives the most amount of resources is the one that is processed quickly and efficiently.
The attention would be integrated into the perceptual or cognitive process itself. The competition occurs because it is impossible to process everything at the same time, the attention predisposes to resolve the competition between inputs. The inputs compete in different brain regions. In the initial phases of vision, the competition will be influenced by exogenous factors such as color or shape. These inputs will eventually reach the most anterior areas (frontal and prefrontal lobes), where decisions are made and, this is where the competition will be influenced by endogenous inputs, competition that will return to the primary regions, so that there is a process of competition in multiple regions of the brain, independent but with a final convergence that determines the perception, how we see, the outside world.
