In This Chapter
Understanding how to grab someone’s attention
Controlling attention when you have it
Digging into attention disorders
Consider the environment around you while reading this book. We doubt that it’s absolutely quiet. Most likely you can hear distractions (perhaps a TV, music, the sound of someone vacuuming). Yet, despite these distractions, you can remain (mostly) focused on what you’re reading. The huge amount of sensory input that everyone is constantly receiving would be overwhelming if humans weren’t able to block out some of it. The psychological mechanism of this filtering and focusing ability is attention.
Attention acts like a spotlight, a focusing device to bring to mind a particular stimulus. It also acts as a filter, blocking out distractions.
In this chapter, we describe the key features of what attracts attention, what doesn’t attract attention (even when it probably should!) and how attention helps you search for things. We also discuss how to control attention, the mechanics of involuntary attention and some clinical disorders of attention.
‘Hey, You!’ Grabbing Attention
Understanding attention is essential in many areas of life. One group that relies on it to make a living are magicians.
In 2008, the prestigious journal Nature Reviews Neuroscience published an article by a number of magicians (including Teller of Penn and Teller fame) explaining how they use knowledge of human cognition to execute their tricks and how this knowledge can help cognitive psychologists understand how the brain works. One sure common skill is misdirection – guiding the audience’s attention away from the real trick. Misdirection involves several aspects of attention that we define and discuss in this section:
- Priming: Where seeing one object or word (the cue) speeds up the processing of a second object or word
- Inattentional blindness: Where people don’t spot or attend to something visually
- Visual searching: Where people have to search the visual environment for a particular object
In the vanishing ball illusion, the magician throws a ball in the air and catches it a few times. On the final throw, the ball seems to disappear in midair. In fact the magician palms the ball, but audience members don’t notice because of inattentional blindness. The magician has misdirected them. To start, she primes the audience by really throwing the ball a number of times (so that people expect the same thing to happen again). Then on the final throw, she cues the audience to look where the ball should be by using the same hand movement and gazing at the imaginary ball – doing so guides the audience’s attention to where she’s looking, because people automatically follow one another’s gaze.
Priming the pump
The simplest explanation for priming is that the presentation of something (an object or word) makes it easier for the brain to activate its stored representation for that something (object or word) later. So, if you hear the word square, you’re quicker to respond to a square when you see it.
Expectation can also be used for priming. American psychologist Michael Posner developed a test called the Posner cueing task, which measures how the attention system responds to different cues.
Participants are presented with a fixation cross (a ‘+’) in the middle of the screen. Then a cue appears, directing their attention to one or the other side of the fixation cross. A target appears, and participants have to respond to the target (for example, by saying what shape it is). The cue can be valid or invalid. On valid trials, the cue predicts the location of the target. On invalid trials, the cue doesn’t predict the location of the target. Neutral trials, in which no cue exists, are also used.
The number of valid and neutral trials is always greater than invalid trials. So, the participants can expect that the cue is going to predict the target location. The results are that the valid cues speed up identification of the target, whereas invalid cues slow it down.
People’s desires can also prime their attention. For example, alcoholics spot alcohol-related objects in a visual scene quicker than non-alcoholics.
Failing to notice the obvious
Inattentional blindness is a phenomenon in which people fail to notice or attend to something in their visual world. In 1998, psychologists Arien Mack and Irvin Rock carried out research showing that people can miss something right before their eyes when their attention is distracted.
Participants were presented with cross shapes and had to identify whether the horizontal bar was longer than the vertical bar. The crosses were on screen for only 200 milliseconds; participants were looking at a fixation cross, not looking directly at the cross shape. People were highly accurate at this task. But when researchers replaced the fixation point with a shape (a triangle, rectangle or cross), 86 per cent of participants didn’t notice the change.
Change blindness is a related and more intriguing phenomenon. People often fail to notice changes to an image that seem really obvious when pointed out to them. Normally, when something moves or changes in front of people, the change grabs their attention because it changes their retinas (creating transients, cell responses to something new).
To produce change blindness, psychologists need to mask these transients. They can do so in several ways:
- Blink: If the image is changed during an eye blink, the change doesn’t attract the person’s attention.
- Flicker: The whole screen blanks out for a brief moment, hiding the location of the change.
- Mud splash: A number of shapes flash on the screen while the change occurs to distract the participant.
- Slow change: If something changes slowly enough, such as the colour of a wall, it doesn’t attract people’s attention.
Change blindness and inattentional blindness often occur in films, with people missing continuity errors or ignoring a camera operator in the shot. Scientific studies of continuity errors show that 90 per cent of people fail to notice them, even if they expect some changes. Change blindness may also be a reason for the type of road accidents in which a driver pulls out into the path of another vehicle because he ‘looked, but failed to see’.
Daniel J. Simons offers these explanations for change blindness:
- Your brain overwrites the first image with the second.
- After your brain stores the first image, you ignore the next one.
- You don’t remember either image for long enough to compare them.
- Your brain stores both images but you don’t consciously compare them.
- You don’t expect changes, so your brain combines the two images mentally.
Another explanation is based on inhibition of return, which is where you don’t look back at somewhere you’ve recently observed. Inhibition of return prevents you from getting stuck looking at one part of an image.
Change blindness typically occurs only for less central aspects of the visual scene and only for things that you don’t expect to change (say, the face of someone you’re talking to). So, part of the attentional system’s role is to prepare you for what’s likely to change. But the result is that it may not provide you with a true representation of the world.
Visual search: Looking for a needle in a haystack
The popular Where’s Wally books (Where’s Waldo in the US) involve trying to find the eponymous hero in a distinctive outfit in a cluttered scene. The task is difficult because the scene contains lots of other people and objects, and many of them share colours and features similar to the target. Cognitive psychologists use a more formal version of this task called the visual search task to understand the role of attention in vision.
In the visual search task, people are shown an image full of different shapes and they have to say whether a particular shape (the target) is present or absent. The researchers record the time taken for people to decide whether the target is present or absent. Before reading on, find the B in Figure 7-1a and the O in Figure 7-1b.
In both displays in Figure 7-1a, the B shares the same features (vertical and curved lines) as the distractors P, so it doesn’t pop out. You have to check each item in turn, searching for the specific conjunction of features, so you take longer to find the target in the top image because of more distractors. In Figure 7-1b, the O is the only shape containing curved lines, so it pops out and the number of distractors has little effect.
By varying the number of other objects (distractors) and the similarity between the target and the distractors, psychologists can discover some interesting facts about visual search and attention:
- If the target is different from all the distractors in terms of a single, simple feature such as colour or shape (as in Figure 7-1b), it tends to pop out and the time taken to find the target stays the same when researchers increase the number of distractors. But to report that the target is absent takes longer and this time period increases with the number of distractors.
- In a conjunction search (searching for a target that shares elements with distracting items), the target doesn’t have a unique single feature but a unique combination of features. Here the time to find a present target increases with each distractor added, and deciding that the target is absent takes about twice as long. Figure 7-2 shows the pattern of results for the two kinds of search (where the search item is present and the search item is absent) and different numbers of distractors.
According to psychologist Anne Treisman’s feature integration theory, attention is the ‘glue’ that binds the features together in visual search. In pre-attentive search, your visual system picks out features (such as colour, shape, size and movement). At this stage, if the target is the only item containing a certain feature, it pops out. But if the target depends on a conjunction of features, it doesn’t pop out and you have to look for it, one item at a time. By attending to an object, you’re able to ‘glue’ the different features together.
Pre-attentive search only allows you to process simple features, but it’s fast – everyone processes all the features at the same time (in a parallel search). To use attention, you need to examine each object one at a time (a serial search), which is slower because you have to attend to each item in turn. On average, people have to examine about half the objects in a display before finding the target. But in order to say that the target is absent, they need to search exhaustively every item, which is why people take about twice as long to respond when the object isn’t present.
‘Now Concentrate!’ Controlling Attention
Implicit in the definition of attention is the idea that you can take control of your conscious experience. Attention shines like a spotlight on a stimulus (or stimuli). It raises awareness of key parts of the thing you’re attending to while dimming others. It selects what reaches your consciousness.
Imagine, for example, that you’re revising for a cognitive psychology exam (reading this book, of course, and writing notes), while the TV’s on, someone’s hollering about dinner and you’re expecting a text message. Attention removes the distraction and focuses on the key task (revising) or tasks (revising and listening out for your mobile phone).
In this section, we cover how you choose (or not) what you attend to. We also describe what happens when you have multiple things to attend to at once and how difficult that is. Plus we explore what factors push your attentional capacity to the limit.
Investigating selective attention
The first thing your brain needs to do when studying is to select the relevant things to attend to: in other words, on what to put the attentional spotlight (or unidirectional microphone for sounds!). Here we look at how the brain selects information to attend to.
Classic studies of auditory attention use a shadowing paradigm (an experimental task in which participants must pay attention to sounds in one ear but ignore the other). Participants wear headphones and their task is to repeat what they hear. Simple, you say. But psychologists make things harder by presenting different messages to each ear (called the dichotic listening task): for example, the message ‘1, 2, 3’ to one ear and ‘4, 5, 6’ to the other ear. When asked to repeat what they hear, participants report hearing ‘1, 2, 3, 4, 5, 6’.
In other dichotic listening tasks, participants have to shadow one ear but ignore the other. They’re then asked to recall information from the attended ear (in which the message was shadowed) and the unattended ear (the one they were supposed to ignore). Participants are nearly perfect at remembering information from the attended ear, but remember very little from the unattended ear. In fact, participants don’t notice whether the language used in the unattended ear swaps from English to German or even if the same word is repeated several dozen times!
Participants do notice, however, if the gender of the speaker in the unattended ear changes. Furthermore, most participants are unaware of an instruction to stop the task in the unattended ear unless it’s preceded by their name. Colin Cherry, a British cognitive psychologist, described this tendency as the cocktail party effect – even if you’re attending to something else, you sometimes hear your name spoken.
Researchers Daniel Simons and Christopher Chabris report a similar effect in the visual domain. They present a video to participants in which two teams (one wearing white and one wearing black) pass balls between themselves. Participants were instructed to count the number of times the team in white passes the ball to each other and to ignore the team in black. During the video, a man in a gorilla suit walks into the middle of the screen, beats his chest and walks off. Less than half the participants noticed the gorilla (try the video out on your friends at http://www.simonslab.com/videos.html).
To explain why people don’t notice things even when they’re in plain sight (or sound!), Donald Broadbent, a British psychologist, proposed a filter theory of attention in the 1950s. His early-selection theory was based on the idea that attention acts as a filter shortly after the senses detect the stimulus. Low-level stimulus properties (such as volume or pitch) are then used to decide what’s to be allowed through the filter. Basically, all unwanted sensory stimulation is sieved out.
Some researchers use the cocktail party effect to criticise the early-selection theory. Specifically, one study criticised the theory by giving mild electric shocks to participants every time a particular word was presented in the unattended ear. This formed a classical conditioning pairing of a word and a shock. When asked to recall the words, participants couldn’t recall the word paired with the shock. But when shown the word, they had a higher skin galvanic response (their hands got a little sweatier), suggesting that they were mildly afraid of the word. This suggests that they had attended to and memorised the word, but not consciously.
Anne Triesman developed the attenuation model in which attention simply reduces the amount of information that can get through the filter. The early filter still blocks out unwanted stimulation, but allows information through that has certain physical properties. Diana Deutsch, British-American perceptual and cognitive psychologist, went further, and suggested that all information is processed and attention simply filters out the unwanted information and the semantic (meaning) level (known as late selection). We present these theories in Figure 7-3.
So which is more accurate: early selection or late selection? Experiments show that during highly demanding tasks, people filter out unwanted information as early as possible. For example, when driving along and having a conversation, the talking stops when you reach a busy junction: the attentional filter prevents distraction for a more demanding task. During easier tasks, however, you can employ late selection.
Getting your divided attention
No doubt you’ve tried multitasking (deliberately focusing on two tasks at the same time), perhaps having a conversation with someone while washing up. How well can you perform the tasks? What about when you’re writing an essay and your roommate asks what you want for dinner? How do you swap from the first task to the second (known as task switching)? Many people finish the sentence they’re writing before answering the question. Both multitasking and task switching are examples of divided attention.
In an experiment on multitasking, participants shadowed one list of words from one ear while ignoring a second list presented verbally or visually. The conditions for list 1 and list 2 were respectively: spoken words/spoken words; spoken words/visual words. Researchers tested recall for both lists and accuracy was higher for the spoken words/visual words condition than when the lists were matched across senses. The message is clear: you can divide attention across multiple tasks as long as they’re dissimilar enough.
One suggestion for when tasks may interfere with each other stems from the working memory model of memory proposed by Alan Baddeley and Graham Hitch in 1976, which contains components for processing visual and verbal material. These two components can process information in isolation. A central executive (the control part of working memory) controls the processing in the two components. Tasks interfere with each other only if they’re using the same component of working memory or when they’re too difficult.
Pushing things to the limit
Although people can multitask a little (see the preceding section), limits apply. If you’re in a room full of noisy people who’re moving around and discussing what they watched on TV the night before, planning an essay in cognitive psychology is nearly impossible. You simply have too much sensory information to filter out.
One of the most useful explanations of a limited capacity system is that of executive control (a series of processes that allow for task switching, focusing; see Chapter 8). Here, working memory and the central executive or episodic buffer (another component of working memory that links short-term and long-term memory) work to plan people’s strategy for completing tasks (see Chapter 8 for more on working memory).
Research shows that executive control allocates attentional resources from one task to another and inhibits automatic responses. Cognitive psychologists have found that executive control is strongly related to tests of inhibition. Executive control also correlates with intelligence, suggesting that more intelligent people can allocate their attention more appropriately than less intelligent people.
Running on Autopilot
Your attention can be under voluntary control – such as when you decide to ignore your ringing phone to carry on watching your favourite TV programme. But your attention can also be automatic – everyone has experienced their attention being drawn to something because of a loud noise or an unusual display. Sometimes, people simply work on ‘autopilot’ – for example, one of us (no names, no blame!) accidentally travelled to college one day instead of to an interview, because that was his normal morning routine and he was too sleepy to prevent the automatic behaviour.
In more serious examples, several aircraft pilots have landed aircraft having apparently ‘forgotten’ to deploy the landing gear, leading the plane to crash land. In many of these cases, the pilots simply went through the landing checklist on ‘autopilot’ without paying attention.
Psychologists have used a number of tools to investigate why this happens. In this section, we cover what factors can interfere with attention and make it worse. We also examine the important effects practice has on attention.
Interfering with attention
Automatic processing can adversely affect your attention. How many times does the letter f appear in the following sentence?
Finished files are the result of years of scientific study combined with the experience of many years.
The most common answer is three but the correct answer is six. Many people seem to miss the ‘f’s when they occur in the word ‘of’.
Words such as ‘of’, ‘the’ and ‘to’ play a functional role in language and appear in most texts. They tend to occur much more often than content words, and so people are more used to them and more practised at reading them, which means that they’re more likely to ignore them. Like anything that’s practised a lot, reading functional words becomes automatic.
The Stroop effect (named after John Stroop, the American psychologist who discovered it) is known as the ‘gold standard’ of automatic processing. The effect is simple: participants are presented with a series of colour words (for example, ‘RED’). The word may be printed in the same colour as what the word means (a congruent condition) – for example, the word ‘RED’ printed in red ink – or in a different colour from its meaning (an incongruent condition) – for example, the word ‘RED’ printed in green ink. Participants have to name the colour the word is printed in.
Participants find the incongruent condition much harder and take longer to name the colours than with the congruent condition: reading is so automatic that psychologists assume that the word’s meaning disrupts people’s ability to name the colour.
The Simon effect is a similar example of automatic processing. Participants are presented with a display in which a symbol is on the left or the right side of the screen. They have to press a left button for one particular cue (for example, an ‘@’) and a right button for a different cue (for example, a ‘#’). If the ‘@’ appears on the left, the trial is considered to be congruent, whereas if it appears on the right, it’s an incongruent trial (and vice versa for the ‘#’). Participants’ reaction time to state that the symbol is present takes longer for the incongruent trials than the congruent ones, confirming that knowledge of spatial positions can interfere with attention.
Practising to make perfect
The nature of attention changes with experience and practice: experts not only focus on different aspects of the task, but also multitask better.
Driving is an obvious example. Novice drivers tend to pay more attention to the car in front of them and its position than expert drivers do. But the latter tend to pay more attention to cars to the side or at junctions (in positions where cars may do unexpected things, such as pull out suddenly).
One suggestion is that practice makes a task more automatic, and so it requires less attentional resources. Executive control is primarily needed to inhibit automatic processing or when automatic processes are unavailable. So, when a behaviour is well practised, it becomes habit and, as a result, you don’t think about the action.
Consider playing the guitar: when you’re learning a new chord, you have to look at your fingers to position them in the right place. But when you’ve practised enough, you simply change to that chord without looking at it.
Another simple aspect of how skill diminishes your awareness of the precise acts involved is through chunking (see Chapter 8 for more on this concept). Chunking is where you group items together to make remembering easier.
When you’re learning the chord of C on the guitar, you have to do four steps: you need to position your forefinger on the b-string, your second finger on the d-string, your ring finger on the a-string, and then strum on all but the e-string. Eric Clapton, however, can chunk all these small aspects into one instruction: ‘play the chord of C’. The cognitive resources to make four responses are simplified into making one response.
Belgium psychologist Bruno Rossion suggests that experts have a wider attentional spotlight, allowing them to see more of a stimuli in one glance than a novice.
When Things Go Wrong: Attention Disorders
Attention is crucial for human survival. Yet neuropsychological conditions exist in which the ability to attend is severely impaired. In this section, we take a look at two attention disorders: spatial neglect and attention deficit hyperactivity disorder.
Ignoring the left: Spatial neglect
Don’t worry, despite the heading this section isn’t going to get all political! Spatial neglect is a relatively common disorder of attention usually caused by damage to the right parietal lobe (a bit of the brain towards the side and back of the head). Patients suffering from spatial neglect appear not to see or attend to half of the visual field (usually the left side – the opposite side to the damage). That is, they can see only what’s on the right side of an object.
Tests of spatial neglect include the following:
- Cancellation tasks: Patients are asked to cross out all the items, but they tend to cross out only those on one side (see Figure 7-4a).
- Line bisection: Patients are asked to mark the middle of the line, but they tend to mark the line to one side, as we show in Figure 7-4b.
- Copying: Patients are asked to copy an image, but they tend to copy only half of the image, as Figure 7-4c depicts.
In all cases, patients can’t detect what’s on the neglected side. Things can be so severe that patients even shave only one side of their face or eat half the food on their plate. Patients with spatial neglect can’t visualise, imagine or even describe the neglected side of a place. In one study, a patient with neglect was asked to imagine and describe a famous square in Milan. The person described the features on the right-hand side of the square. When asked to imagine and describe the square from the opposite side, the person again described the right-hand side (the opposite side from before). Clearly, someone with neglect doesn’t have a problem with perception, but attention.
Although patients with neglect seem unable to attend to one side, they’re unconsciously aware of the neglected side. British neuropsychologists John Marshall and Peter Halligan conducted a study in which patient PS was given two pictures: house A was a normal line drawing (see Figure 7-4c); house B was identical, except that it had flames coming out of the upper window on the neglected side. PS was asked which house she preferred. On 15 out of 17 trials, PS chose the one without the flames but was unable to explain her preference.
Patients with neglect can also identify symmetry in the neglected side. These findings suggest that they do have some unconscious awareness of the neglected side. In other words, some things can enter people’s minds without attention and without conscious awareness.
Having trouble paying attention: ADHD
Attention-deficit hyperactivity disorder (ADHD) is a common childhood psychological disorder. It occurs in 3–5 per cent of Western children and is characterised by an inability to focus or maintain attention for a long time, leading to restlessness and potentially aggression. Children with ADHD often interrupt others and are impatient.
Cognitive tests of children with ADHD usually involve vigilance designs, in which participants have to respond when they see a particular stimulus (for example, a square) among lots of other stimuli (for example, triangles). Each stimulus is presented one after another, with (crucially) the target stimulus presented very infrequently. Children with ADHD perform very badly at this type of task. They can easily name squares and triangles, however, showing that the disorder is one of sustaining attention.
Another experiment asks participants to respond with a button press when they see an X and a different key when they see an O. Children with ADHD perform well at this easy task. An instruction to stop the response when a sound is played at the same time as the X or O occurs on a few trials (the stop-signal paradigm). Children with ADHD are less likely to stop on these trials than other children, showing that children with ADHD have problems inhibiting their responses.
One treatment for ADHD is the stimulant methylphenidate, which makes the brain more responsive. The idea is that the brains of children with ADHD need more stimulation to show the same activation as children without ADHD. Methylphenidate makes children with ADHD perform better at the stop-signal experiment and makes them better able to inhibit.
