Attention is a complex concept which refers to our ability to actively process specific information. It allows us to filter out all the signals which are irrelevant for the task at hand: smells, sounds, physical sensations, images - even internal thoughts. If we experienced all this consciously it would lead to a cognitive overload, and it would be impossible to focus on anything specific. Attention, however, 'highlights' important information, making it 'stand out' among all the numerous distractions.
In this post, I will discuss some binary types of attention and discuss some of the main theories of attention. In relation to cognitive psychology, I will talk about some disorders which can reveal how attention works in a normal brain, and will briefly touch upon the role of memory in attention.
In this post, I will discuss some binary types of attention and discuss some of the main theories of attention. In relation to cognitive psychology, I will talk about some disorders which can reveal how attention works in a normal brain, and will briefly touch upon the role of memory in attention.
Types of attention
There are several binary distinctions by which we can classify attention. Some of them are:
1. Covert / overt attention
Overt attention means directing our sense organs (in particular, eye gaze) to the attended stimuli; covert attention, however, is a mental focus on something different from what we perceive with our sense organs. Example of this can be looking at the pages of a book while thinking of some event which had happened earlier in the day; in this case, your focus on this thought/memory is covert. However, if you were focusing on what you are reading about, such attention could be called overt.
2. Endogenous (goal-directed, top-down) / Exogenous (stimulus-driven, bottom-up) attention
Endogenous attention is a conscious, intentional direction of focus; it is under our control. For example, when we concentrate on exam, we apply goal-directed attention by 'forcing' ourselves to attend to a specific task. On a contrary, exogenous attention is unconscious and is driven by an external stimuli such as loud noise or sudden movement. We attend to these stimuli whether we want or not. This ability enables us to react to dangerous situations before even realising what happened.
3. Serial / parallel processing
The way we process information is closely linked to attention, so I will look at this distinction as well. The idea behind serial processing is that encountering an object we process its features - such as colour, shape, direction and so on - in a series, one thing at a time. Parallel processing is the ability of mind to process multiple signals of differing quality simultaneously, and to compare them to the stored images/memories to understand what it is that we are perceiving.
This distinction provoked an on-going debate among the cognitive psychologists: which type of processing information is really at work when we attend to any particular object?
1. Covert / overt attention
Overt attention means directing our sense organs (in particular, eye gaze) to the attended stimuli; covert attention, however, is a mental focus on something different from what we perceive with our sense organs. Example of this can be looking at the pages of a book while thinking of some event which had happened earlier in the day; in this case, your focus on this thought/memory is covert. However, if you were focusing on what you are reading about, such attention could be called overt.
2. Endogenous (goal-directed, top-down) / Exogenous (stimulus-driven, bottom-up) attention
Endogenous attention is a conscious, intentional direction of focus; it is under our control. For example, when we concentrate on exam, we apply goal-directed attention by 'forcing' ourselves to attend to a specific task. On a contrary, exogenous attention is unconscious and is driven by an external stimuli such as loud noise or sudden movement. We attend to these stimuli whether we want or not. This ability enables us to react to dangerous situations before even realising what happened.
3. Serial / parallel processing
The way we process information is closely linked to attention, so I will look at this distinction as well. The idea behind serial processing is that encountering an object we process its features - such as colour, shape, direction and so on - in a series, one thing at a time. Parallel processing is the ability of mind to process multiple signals of differing quality simultaneously, and to compare them to the stored images/memories to understand what it is that we are perceiving.
This distinction provoked an on-going debate among the cognitive psychologists: which type of processing information is really at work when we attend to any particular object?
Feature Integration Theory
In 1980, Anne Treisman suggested that we process information in two stages, employing parallel processing in the first and serial processing in the second stage. The first stage is called pre-attentive stage, and involves unconscious parallel processing of the object's features. During this stage, features such as colour, shape etc. are processed by different parts of the brain involuntary, before we even realise which object it is we see.
Second stage is the focused attention stage which involves serial processing. During this stage, individual features get combined and we become conscious of an object as a whole - one at a time. To combine the features into a recognisable object attention is needed.
There are two types of a visual search task which Treisman used to test the theory: conjunction search and feature search. Feature search (on the left) requires finding an object with only one feature (here: find red shapes), and can be performed pre-attentively; features will 'pop out' and form an illusory pattern. On the contrary, conjunction search (on the right) requires conscious attention; participants need to analyse every object serially to find required object (here: find a red circle).
Second stage is the focused attention stage which involves serial processing. During this stage, individual features get combined and we become conscious of an object as a whole - one at a time. To combine the features into a recognisable object attention is needed.
There are two types of a visual search task which Treisman used to test the theory: conjunction search and feature search. Feature search (on the left) requires finding an object with only one feature (here: find red shapes), and can be performed pre-attentively; features will 'pop out' and form an illusory pattern. On the contrary, conjunction search (on the right) requires conscious attention; participants need to analyse every object serially to find required object (here: find a red circle).
Balint's syndrome
Balint's syndrome may be caused by bilateral posterior parietal lobes, and leads to inability to 'bind' different objects together and perceive a visual field as a whole. It is also referred to as 'simultagnosia': inability to bind simultaneously happening things in one entity.
How can it be that, despite being able to see and process various objects, people with Balint's syndrome fail to see the 'big picture'? And, what can we say about a normal brain, having considered such a disability?
As I said earlier, attention allows us to filter out all the unnecessary information to avoid information overload. Information which is attended to is composed into a salience map: a map which represents a saliency - or, things that stand out - of a corresponding visual field. This is done by bottom-up processing of separate objects/features such as depth, colour etc. The picture below demonstrates a location in our visual field and corresponding saliency map.
But how come we are able to see and understand the 'big picture' if our mind only sees certain things to be salient? Here, top-down mechanisms make their contribution. They compare features that we see with the stored memories and expectations and allow us to see and understanding the meaning of the surroundings without consciously attending to every bit of information contained in it.
Considering this, it seems like the top-down processing mechanism might be impaired in the patients with Balint's syndrome, so that the individual components which they see fail to be compared with the stored knowledge about them and bind into a meaningful picture.
How can it be that, despite being able to see and process various objects, people with Balint's syndrome fail to see the 'big picture'? And, what can we say about a normal brain, having considered such a disability?
As I said earlier, attention allows us to filter out all the unnecessary information to avoid information overload. Information which is attended to is composed into a salience map: a map which represents a saliency - or, things that stand out - of a corresponding visual field. This is done by bottom-up processing of separate objects/features such as depth, colour etc. The picture below demonstrates a location in our visual field and corresponding saliency map.
But how come we are able to see and understand the 'big picture' if our mind only sees certain things to be salient? Here, top-down mechanisms make their contribution. They compare features that we see with the stored memories and expectations and allow us to see and understanding the meaning of the surroundings without consciously attending to every bit of information contained in it.
Considering this, it seems like the top-down processing mechanism might be impaired in the patients with Balint's syndrome, so that the individual components which they see fail to be compared with the stored knowledge about them and bind into a meaningful picture.
Left neglect
Damage of a right hemisphere can lead to an impairment called left neglect. Such patients neglect left part of their visual field as if they don't see it; when asked, they can't reproduce information on the left and recall ever seeing it. For example, here you can see a typical task for patients with left neglect: they are asked to copy the pictures (images on the left), and end up only drawing their right parts (images on the right); they don't realise they have produced an unfinished image.
However, some information from the left visual field still gets in; it's just that the patients can not consciously access it. For example, it has been shown that words presented to the patients' left visual field could prime the words in the right visual field, decreasing the response time (Halligan & Marshall (1994); Kolb & Whishaw (1990)). Read more on Semantic Priming in Psychology of Language section.
However, some information from the left visual field still gets in; it's just that the patients can not consciously access it. For example, it has been shown that words presented to the patients' left visual field could prime the words in the right visual field, decreasing the response time (Halligan & Marshall (1994); Kolb & Whishaw (1990)). Read more on Semantic Priming in Psychology of Language section.
Another evidence stems from the fact that in some cases information from the left visual field gets 'relocated' to the right side of their picture (allochiria). The reason behind the case with a clock is, however, ambiguous: it is unclear whether a patient drew all the 12 numbers due to the knowledge that there are supposed to be 12 numbers on a clock or because they actually processed all the 12 numbers without realising it.
Similar mislocation of stimuli was found to occur in about 25% of normal people under certain conditions (Marcel et al., 2004). In the study, both hands of a participant were stimulated at the same time with tapping; however, the participant was told to only pay attention to one hand. In cases when stimulus became more salient in an UNattended hand (pattern or strength of tapping changed), the sensation migrated to the attended hand and fused with or replaced the attended stimulus. However, Marcel et al. suggested that latencies (phase between the stimulus delivery and reaction) reflecting the simultaneity of the stimuli showed that unconsciously their locations were identified correctly. He also showed that for the sensation migration to occur it was necessary to present stimulus to both hands, not only unattended one.
This finding shows that mislocation to the focus of spatial attention is quite common in healthy people, especially when binding is prevented. The phenomenon appears equivalent to allochiria, thus suggesting a premorbid susceptibility to spatial migration that can be exaggerated by brain damage.
This finding shows that mislocation to the focus of spatial attention is quite common in healthy people, especially when binding is prevented. The phenomenon appears equivalent to allochiria, thus suggesting a premorbid susceptibility to spatial migration that can be exaggerated by brain damage.
Just to finish you off: video of a dog with a left neglect syndrome after it had a stroke.