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Chapter 4: Key Concepts of Selective and Divided Attention
- 1. © 2010 by W. W. Norton & Co., Inc. Paying Attention Chapter 4 Lecture Outline
- 2. Chapter 4: Paying Attention Lecture Outline Selective Attention Divided Attention Practice
- 3. Selective Attention Selective attention refers to the skill through which one focuses on one input or one task while ignoring other stimuli
- 4. Selective Attention Shadowing (repeating an audio track) Dichotic listening—Different messages to each ear Attended channel—Listen to this one Unattended channel—Ignore this one
- 5. Selective Attention Count passes from players with white shirts Participants ignore those with black shirts People do not notice the gorilla DEMO 1 DEMO 2
- 6. Selective Attention Cocktail party effect Other conversations tuned out Unattended channel can be noticed The participant’s own name Words of high personal significance Boost attended items and dampen unattended items
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- 8. Selective Attention Sometimes effects of attention are so strong that we fail to see stimuli that are directly in front of our eyes
- 9. Selective Attention Look at a fixation target Attend to another part of the screen No warning leads to failure to detect change
- 11. Selective Attention Inattentional blindness: “no perception without attention” Unconscious perception can still occur in the absence of attention
- 12. Selective Attention People asked to judge bars Do not perceive fins but still see illusion Typical illusion
- 13. Selective Attention Change blindness: inability to detect changes in scenes DEMO 1 DEMO 2 DEMO 3 Other DEMos
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- 20. 改變盲的意涵 The absence of visual representation Grand illusion (Noe, 2002) “…seeing constitutes an active process of probing the external environment as though it were a continuously available external memory.” (O’Regan, 1992) Do people not preserve any visual representation in their brain?
- 21. Multiple stages in CD Retrieval and ComparisonEncoding Retention Encoding Time Change or No change? Is there any change?
- 22. Five possible hypotheses Simons (2000)
- 23. Selective Attention Early-selection hypothesis Late-selection hypothesis Attended input Unattended input Attended input Unattended input Consciousness Consciousness
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- 26. Selective Attention Early- and late-selection hypotheses are both true Stimuli that are not attended to have effects on perception, which indicates late selection Electrical brain activity for attended inputs differs within 70 ms from unattended inputs, which indicates early selection
- 27. Selective Attention Selection depends on resources Perceptual load theory (Lavie, 1994) Complex stimuli involve more effort, leading to early selection (high perceptual load) Easy stimuli involve less effort, leading to late selection (low perceptual load) Perceptual load vs cognitive load? 27
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- 31. Selective Attention Selection as a form of priming Lower threshold leads to easier recognition Attended channel has lower threshold Your name is frequent and is primed even when unattended 31
- 32. Selective Attention Posner and Snyder (1975) found two kinds of priming related to attention Stimulus-based priming does not involve effort Expectation-based priming does involve effort
- 34. Selective Attention Low-validity condition Many misled trials Primed condition faster than neutral Misled same as neutral Facilitation only
- 35. Selective Attention High-validity condition Primed condition much faster than neutral Expectation augments repetition priming Misled slower than neutral condition Expectation limited in capacity Wrong expectation interferes with correct detectors
- 36. Selective Attention Stimulus-based priming Fast Few costs Expectation-based priming Slow More costly 36
- 37. Selective Attention Spatial attention the ability to focus on a particular position in space
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- 40. Selective Attention What do you see when you adjust the size of the beam?
- 41. Selective Attention Eye movements Around 180 ms Shifts in attention As early as 150 ms 41
- 42. Selective Attention 42 Parietal and frontal cortex are involved in attention
- 43. Selective Attention Do we attend to positions in space or to objects? Object-based attention Space-based attention: unilateral neglect syndrome Feature-based attention?
- 44. Selective Attention Unilateral neglect syndrome Damage to the right parietal lobe Cannot attend to the left side of space Unable to attend to left half of clock
- 45. Selective Attention However, some experiments suggest that the deficit is also object-based
- 46. Selective Attention 46 Patients see targets in red Item rotates Patients continue seeing targets in red Intact side
- 47. Selective Attention 47 Larger cost when the misled trial is on the uncued triangle
- 48. Selective Attention 48 Narrow attention allows you to bind things together Broad attention allows you to detect features but not bind them
- 49. Selective Attention Summary of selective attention Both facilitating desired input and inhibiting unwanted input Attention directed both to an object and to space Flexibility of early and late attention Attention is not a single process or a particular mechanism
- 50. Divided Attention Julius Cesar was praised for multitasking (dividing his attention) cognitive budget
- 51. Controlled vs. Automatic Processing Automatic processing Requires no conscious control Controlled processing Requires conscious control
- 52. Divided Attention Some cognitive resources are specialized For instance, verbal and spatial tasks can sometimes be performed spatially because each draws upon different resources
- 53. Divided Attention Other cognitive resources are general
- 54. Gauging Your Distraction During Driving http://www.nytimes.com/interactive/2009/0 7/19/technology/20090719-driving- game.html
- 55. Divided Attention 55 Success drops when talking on a cell phone Passenger adjusts to driving conditions
- 56. Divided Attention 56 Most similar Least similar Somewhat similar
- 57. Divided Attention Several task-general cognitive resources have been proposed, such as: Response selector Central executive
- 58. Divided Attention Executive control is strongly connected with working memory Necessary for overcoming habitual responses Moving eyes away from a cue
- 59. Divided Attention Executive control Works to keep the desired goal in mind Serves to inhibit automatic responses
- 60. Divided Attention The prefrontal cortex is particularly important to executive control Goal neglect Bad planning Perseveration Rigid planning No damage
- 61. Practice Practiced skills require less executive control
- 62. Practice Why does practice improve performance? Complex tasks get broken into parts With practice, these parts go from being controlled to being automatic
- 63. Practice Controlled tasks Automatic tasks Flexibility Yes No Attention Yes No Novel Yes No
- 64. Practice Name the color ink Easy Hard
- 65. Practice Automaticity of number makes counting and saying the number harder
- 66. Practice Summary of divided attention and practice Tasks require resources, and you cannot “spend” more resources than you have Some resources are task-specific and others are task-general If two tasks make demands upon the same resources, the result will be interference Practice increases the automaticity of a task, resulting in the need for fewer cognitive resources
- 68. 1. Which of the following is a failure of selective attention? a) You are in the basement washing clothes and you hear the dog bark unexpectedly upstairs. b) You are able to change the radio station while driving. c) While you are working on your problem set in the living room, you are thrown off track when your sister changes your favorite radio station. d) While upstairs talking to your best friend, you pretend not to hear your brother asking you to help clean the kitchen.
- 69. 2. Which statement about visual attention is LEAST accurate? a) Stimuli that are expected are very likely to catch our attention. b) The only way to point attention to a place is to point our eyes in the direction. c) By priming our detectors, we make expected stimuli more likely to be noticed and remembered. d) Attention can be directed toward specific areas of space but not specific objects.
- 70. 3. You are at a cocktail party conversing with a friend. In this situation, you are MOST likely to hear a) whether the person behind you is speaking intelligently or foolishly. b) whether it is a man or a woman standing behind you talking. c) that the couple beside you are talking about a movie you just saw and loved. d) that your name is being called out by the person next to you.
- 71. 4. Which of the following statements applies to stimulus-based priming but not to expectation-based priming? a) It has an immediate effect on attention. b) It has a cost attached. c) It leads to faster recognition of subsequent related stimuli. d) It is bottom-up.
- 72. 5. In the absence of attention: a) there is no perception. b) participants still consciously perceive stimuli if the stimuli are simple enough. c) participants can perceive most aspects of the world but are not influenced by what they perceive. d) stimuli may not be consciously perceived but can still have an influence on the perceiver.
- 73. 6. In a study of spatial attention, participants were given a neutral, correct, or misleading cue about where on the screen a stimulus would appear. What is an explanation for what happened on trials with misleading cues? a) There were costs because spatial attention is a limited-capacity system. b) There were costs because the spotlight of attention had moved to the misled location and had to move back. c) both a and b d) neither a nor b
- 74. 7. According to most current thinking, what process is impaired (in the affected half of space) in patients with unilateral neglect syndrome? a) disengaging attention from its current focus b) moving attention to a new focus c) locking attention on to a new focus d) holding attention on its current focus
Notas del editor
- Suggestion: Add a picture to this slide that has a hidden and unexpected element. Searching online for “face in coffee beans” images will turn up a number of good candidates in which it is difficult to spot a face hidden among a pile of coffee beans.
- Attention studies sometimes employ a task known as shadowing. Different information is presented to each ear via headphones. This is known as dichotic listening. The participant pays attention to the information presented to one ear (the attended channel) while ignoring information presented to the other (the unattended channel).
- Results from these studies suggest that unusual characteristics of the unattended channel go unnoticed. Similar effects happen in visual studies; for example, in a classic study, participants who were asked to count the number of basketball passes failed to notice a person in a gorilla suit enter the scene.
- There are some important exceptions, where certain pieces of information will be noticed even if presented to the unattended channel. The participant’s own name, or any words of high personal significance, will be noticed even in the unattended channel. This pattern is observed in real-life situations and sometimes called the cocktail party effect.
- For instance, if participants are asked to look at a fixation target while attending to another part of the screen, they may fail to notice changes in shape to the fixation target. This phenomenon is known as inattentional blindness.
- A phenomenon similar to inattentional blindness occurs when a distracted person cannot find something in the refrigerator, even if it is directly in front of the eyes. Chabris and Simons (2010) call attention to the reports of traffic accidents in which (for example) a driver says: “I never saw the bicyclist! He came out of nowhere! But then— suddenly—there he was, right in front of me.” Or, as a much more mundane case, you go to the refrigerator to find the mayonnaise (or the ketchup, or the juice) and fail to find it, even though it is directly in front of you.
- From studies of inattentional blindness, one might be tempted to conclude that there is “no perception without attention.” However, other studies demonstrate that unconscious perception still occurs in the absence of attention.
- For example, participants’ judgments of line length are influenced by the presence of “fins” that cause the Müller-Lyer illusion, even if they do not consciously see the fins.
- Other studies of attention focus on a phenomenon known as change blindness, the inability of observers to detect changes in scenes they are looking directly at. See if you can detect the differences between the following pairs of pictures:
- Early studies of attention focused on when the perceiver selects the desired input. According to the early-selection hypothesis, the unattended input receives little to no analysis. According to the late-selection hypothesis, all input receives analysis but only the attended input reaches consciousness or is remembered.
- Both the early- and late-selection hypotheses capture part of the truth. For instance, the study discussed earlier showing that unattended stimuli have effects on perception seems to be a case of late selection. However, the electrical activity of the brain for attended versus unattended inputs differs within 70 ms of stimulus presentation, suggesting early selection.
- If this input is particularly complex, then the processing of this input will demand a lot of effort and a lot of cognitive resources. In this case, little effort will be left over for other stimuli, with the consequence that the other stimuli receive less processing, leading to a data pattern consistent with early selection. In contrast, if the attended input is relatively simple, processing will demand few resources, leaving more available for the unattended inputs. Here the unattended inputs will probably receive more analysis, and so we will see the pattern of late selection.
- The proposal, then, is that people can literally prepare themselves for perceiving by priming the suitable detectors. Let’s hypothesize in addition that this priming is not free. Instead, you need to spend some effort or allocate some resources in order to do the priming, and let’s suppose that these resources are in limited supply.
- An experiment by Posner and Snyder (1975) illustrates that there are two kinds of priming related to attention. One kind of priming is stimulus based, and the other is expectation based. For this type of study, the dependent variable is the response time to make a decision about the stimuli.
- In the low-validity condition, misled trials occurred four times as often as primed trials (80% versus 20%). Therefore, participants had reason not to trust the primes and, correspondingly, had no reason to generate an expectation based on the primes. In the high-validity condition, things were reversed: Now primed trials occurred four times as often as misled trials. Therefore, participants had good reason to trust the primes and good reason to generate an expectation based on the primes.
- Posner and Snyder (1975) found in the low-validity condition that the primed condition was faster than neutral. This demonstrates an effect of repetition priming; the receptors were “warmed up.” But, the misled condition was not any slower than neutral. Warming up the “wrong” detector does not take activation away from the correct one
- Posner and Snyder (1975) found in the high-validity condition that the primed condition was much faster than neutral. This demonstrates an additional effect of expectation in addition to repetition priming. Further, the misled condition was slower than the neutral condition. Expectation is limited in capacity; the “wrong” expectation interferes with activating the correct detectors.
- Studies of spatial attention examine the ability to focus on a particular position in space and to be prepared for stimuli appearing in that position. Suggestion: An image of a sports referee making an out-of-bounds (or in-bounds) call works nicely to demonstrate this concept.
- For example, when detecting a stimulus on the right or left side of the screen, participants benefit if an arrow provides a cue indicating on which side the stimulus is about to appear (Posner et al., 1980). Note that directing spatial attention is different than moving the eyes.
- Spatial attention is sometimes thought of as a “searchlight.” We can move this searchlight in space, as well as adjust the size of the “beam.”
- Shifts in attention are not the same as shifts in eye movements. They occur earlier.
- Evidence from unilateral neglect syndrome, caused by damage to the right parietal lobe, could be argued to support a space-based view. These individuals cannot attend to the left side of space. However, some experiments suggest that the deficit is also object-based.
- Evidence from unilateral neglect syndrome, caused by damage to the right parietal lobe, could be argued to support a space-based view. These individuals cannot attend to the left side of space. However, some experiments suggest that the deficit is also object-based.
- Evidence from unilateral neglect syndrome, caused by damage to the right parietal lobe, could be argued to support a space-based view. These individuals cannot attend to the left side of space. However, some experiments suggest that the deficit is also object-based.
- Unilateral-neglect patients attended to the red circle, initially presented on the right, even after it rotated to the left side of the object. Healthy participants also show a mixture of spatial and object-based attention.
- Participants viewed a computer display like the one shown on the left. They pointed their eyes at the fixation target in the center of the screen, and their task was to detect a target that could appear either in the left rectangle or the right, and either at the rectangle’s top or the rectangle’s bottom. Before the target appeared, a signal cued where it was likely to appear, and the signal was generally accurate. Of special interest, though, are the trials in which the signal was not accurate. In one trial, for example, the cue might indicate that the target would appear at location 1 (left rectangle, top), but then the target would instead appear somewhere else. Consistent with other studies, participants were slower (showed an “RT cost”) if they were misled in this way. However, the cost was smaller (about 35 ms) if the target was in the cued rectangle (in this example, at location 2). The cost was larger (roughly 50 ms) if the target appeared in the uncued rectangle (in this example, location 3). (No numbers were visible in the actual displays.)
- Each spotlight of attention yields different costs and benefits. On the left the participant will be able to quickly catalogue all the features that are in view (because she’s looking at all the inputs simultaneously), but she’ll also fail in her search for the red + horizontal combination: Her catalogue of features tells her that both redness and horizontality are present, but the catalogue doesn’t help her in figuring out if these features are linked or not. The observer in Figure 4.13B, in contrast, has focused her mental spotlight and so is carefully looking at just one stimulus at a time. This process is slower, because she’ll have to examine the stimuli one by one, and therefore this observer will certainly be influenced by set size. But this focusing of attention gives the participant the information she needs: If, at any moment, she’s only analyzing one item, she can be sure that the features she’s detecting are all coming from that item.
- Summary of selective attention: Attention involves both facilitating the processing of desired input and inhibiting the processing of unwanted input. Attention can be directed to both what the object is as well at where it is in space. There is some flexibility in when the effects of attention will take place (early or late). What we think of as attention is not a single process or a particular mechanism.
- Divided attention refers to the skill of performing multiple tasks simultaneously. This is only possible when the sum of the tasks’ demands is within the “cognitive budget.” Julius Caesar was praised for his ability to multitask.
- For instance, speaking on a cell phone (even with a hands-free device) interferes with the ability to drive, even though the two tasks are seemingly very different.
- In one study, some participants were told to drive eight miles down the freeway and exit at a rest stop; during this simple task, they were talking with a passenger in the car. A second group of participants had the same driving task, but they were talking on a cell phone. The results showed a huge difference between the groups.
- Participants were asked to shadow one list while memorizing another. The first condition (hear words + hear words) involves very similar tasks; the second condition (hear words + see words) involves less similar tasks; the third condition (hear words + see pictures), even less similar tasks. The data show that participants are faster when the items are most dissimilar and slowest when items are most similar (see Figure 4.14).
- A response selector that is required for selecting and initiating responses, both physical and mental. A central executive is required to set goals and priorities, choose strategies, and direct the function of many cognitive processes.
- It is also believed to inhibit automatic or habitual responses when a situation requires a novel response. Kane et al. (2001) found that individual differences in working memory did not predict the ability to move the eyes toward a cue (the automatic response), but did predict the ability to move the eyes away from a cue (a novel response).
- With this context, the proposal is that executive control is a mental resource needed whenever you want to avoid interference from previous habit (including habits supplied by memory, and habits triggered by situational cues). This control provides two functions: First, it works to maintain the desired goal in mind, so that this goal (and not habit) will prevail in your choice of strategies and actions. Second, the control serves to inhibit automatic responses, helping ensure that these responses will not occur.
- Goal neglect—relying on habitual responses that are contrary to the goals of a particular task Perseveration—the tendency to produce the same response over and over when the task requires a change in response
- As a task becomes more practiced, it requires fewer cognitive resources. As the ability becomes more automatic, executive control and the response selector are needed less and less. Suggestion: Include a photo of someone practicing a sport on this slide.
- Complex tasks—like playing tennis, playing the piano, or driving a car—can by themselves create problems in divided attention. With practice, components of the task change from being a controlled process to being an automatic one.
- Controlled tasks are novel and require flexibility in one’s approach. These tasks require attention and cannot be carried out if the person is busy with another task. Automatic tasks are well practiced and do not require flexibility. These tasks require little or no attention and can be carried out if the person is also busy with another task.
- The downside of automaticity is seen in tasks that require the participant to override an automatic response. The Stroop task illustrates the high automaticity of reading. Try to name the ink color and do not read the word.
- In this variant of the Stroop task, try to identify how many symbols are present in each row. This also illustrates the automaticity of reading the numbers.
- Correct answer: c Feedback: This is a failure since changing the channel causes you to lose your concentration. If selective attention worked, there would be no loss of concentration when the channel was changed.
- Correct answer: b Feedback: We can switch our attention without moving our eyes.
- Correct answer: d Feedback: Your name is highly primed and hence likely to be easily recognizable even when you are not paying attention to a conversation.
- Correct answer: d Feedback: Stimulus-based priming is based on perceptual aspects of a stimulus and hence is bottom-up.
- Correct answer: d Feedback: Perception is possible without attention. That is you can have a response without knowing why.
- Correct answer: c Feedback: The costs because of limited-capacity and because attention had moved to the misled location.
- Correct answer: a Feedback: What happens is that those with neglect cannot stop focusing on the intact field, which leads them to “neglect” the impaired side of their visual field.