Chapter 6 Visual Attention.

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1 Chapter 6 Visual Attention

2 注意力對於知覺是必要的嗎？ 注意力可以促進知覺表現嗎？
Figure 6.1 Where is Justin Bieber? (Extra credit: Where is Rihanna? Miley Cyrus?) Figure 6-1 p128

3 選擇性注意力（selective attention）
注意某些刺激而忽略其他的 眼動（eye movement）是一個基本的選擇機制，但眼動並非選擇性注意力的必要條件 William James (1890) Millions of items…. Are present to my senses which never properly enter my experience. Why? Because they have no interest for me. My experience is what I agree to attend to……Everyone knows what attention is. It is the taking possession by the mind, in clear an vivid form, of one out of what seem several simultaneously possible objects or trains of thought…….It implies withdrawal from some things in order ot deal effectively with others.

4 由眼動瞭解選擇性注意力 Saccades Fixation (1st)

5 Figure 6. 2 Scan path of an observer freely viewing a picture
Figure 6.2 Scan path of an observer freely viewing a picture. Fixations are indicated by the yellow dots and saccadic eye movements by the red lines. Notice that this person looked preferentially at areas of the picture such as the statues and lights but ignored areas such as the fence and the sky. Figure 6-2 p129

6 Figure 6.3 When a basketball player looks to the right while paying attention to a teammate off to the left, he is covertly attending to the teammate. Figure 6-3 p129

7 Bottom-up control of selective attention
stimulus salience (defined by color, contrast and orientation) Saliency map

8 Figure 6.4 The red shirt is highly salient because of its color compared to the rest of the scene.
Figure 6-4 p130

9 Figure 6. 5 (a) A visual scene
Figure 6.5 (a) A visual scene. (b) Saliency map of the scene determined by analyzing the color, contrast, and orientations in the scene. Lighter areas indicate greater salience. Figure 6.5 (a) A visual scene. (b) Salience map of the scene determined by analyzing the color, contrast, orientations in the scene. Lighter areas indicate greater salience. (Reprinted from Vision Research, 42, Parkhurst, D., Law, K., & Niebur, E., Modeling the Role of Salience in the Allocation of Overt Visual Attention, (2002).) Figure 6-5 p131

10 Figure 6. 6 Stimuli used by Vo and Henderson (2009)
Figure 6.6 Stimuli used by Vo and Henderson (2009). Observers spent more time looking at the printer (in B) than at the pot (in A), shown inside the yellow rectangles (which were not visible to the observers). Figure 6-6 p131

11 由上而下的（top-down）控制方式 對於場景的基模引導凝視的方式（落在有意義的區域) 作業目標引導凝視落在作業相關的物體上
Dynamic environment experiment, Jovancevic-Misic and Hayhoe (2009) Figure 6.7 Sequence of fixations of a person making a peanut butter sandwich. The first fixation is on the loaf of bread. Figure 6-7 p132

12 注意力對於知覺是有必要的嗎？ 沒有必要 Li (2002)
Ss judge if letters in the middle are the same Ss are 76% correct on whether the scene appeared：缺乏選擇性注意力時仍可能產生某些知覺經驗 Figure 6.21 (a–c) Procedure for Li and coworkers’ (2002) experiment. See text for details. (d) Results of the experiment. Performance is the percent correct when carrying out the central task compared to the percent correct when not carrying out the central task. Performance drops only slightly for the scene task but drops to near chance for the colored-disc task. Figure 6-21 p140

13 Reddy et al. (2007) Central task Peripheral task Dual task
Some types of information are perceived without attention and some are not.

14 有必要 不注意盲(Inattentional blindness Simons and Chabris (1999)
 Cartwright-Finch and Lavie (2007) Figure 6.16 Inattentional blindness experiment. (a) The cross display is presented for five trials. One arm of the cross is slightly longer on each trial. The subject’s task is to indicate which arm (horizontal or vertical) is longer. (b) On the sixth trial, the subjects carry out the same task, but a small square is included in the display. After the sixth trial, subjects are asked if they saw anything different than before. Figure 6-16 p138

15 注意力可以促進知覺處理嗎？ 注意力導向之處的知覺處理較有效率 Precueing (cueing) task (M. Posner)
方塊出於箭號提示側時，反應較快（凝視在中央的十字) Figure 6.8 Procedure for the (a) valid task and (b) invalid task in Posner and coworkers’ (1978) precueing experiment. See text for details. (c) The results of the experiment. The average reaction time was 245 ms for valid trials but was 305 ms for invalid trials. Figure 6-8 p133

16 Figure 6.9 Spatial attention can be compared to a spotlight that scans a scene.
Figure 6-9 p133

17 增加水平bar 亦然 注意力對於知覺的促進效果以「物體」為單元而散播 R Egly AC=AB RTB<RTC
Figure 6.10 In Egly and coworkers’ (1994) experiment, (a) a cue signal appears at one place on the display, then the cue is turned off and (b) a target is flashed at one of four possible locations, A, B, C, or D. Numbers are reaction times in ms for positions A, B, and C, when the cue appeared at position A. Figure 6-10 p134

18 Figure 6. 11 (a) Stimulus in Figure 6
Figure 6.11 (a) Stimulus in Figure 6.10 but with a horizontal bar added (Moore et al., 1998). (b) Possible animal lurking behind a tree (see Chapter 5, page 114). Figure 6-11 p134

19 注意力真的能讓物體看來更「清晰」嗎？ 注意力是促進「知覺」還是作「反應」？測量到的注意力效果反映的是什麼？
例如：「哪一個比較亮？」--注意力是否影響？ 但即使如此，也有可能是來自於受試有成見認為注意的刺激會比較清楚

20 報告「對比較強的光柵朝向哪個方向？」（Carrasco et al., 2004）
結果當對比其實相同時，注意側（160 ms 前閃光點）被報告的的機會增加 Figure 6.12 Procedure for Carrasco and coworkers’ (2004) experiment. See text for explanation. Figure 6-12 p135

21 Attention Can Influence Physiological Responding
O’Craven (1999) –注意臉或房子，造成FFA與PPA不同的活動程度 Figure 6.13 (a) Superimposed face and house stimulus used in O’Craven and coworkers’ (1999) experiment. (b) FFA activation when the subject attended to the face or the house. (c) PPA activation for attention to the face or the house. Figure 6-13 p135

22 Datta and DeYoe (2009) Attention maps show directing attention to a specific area of space activates a specific area of the brain. Figure 6.14 (a) Subjects in Datta and DeYoe’s (2009) experiment directed their attention to different areas of this circular display while keeping their eyes fixed on the center of the display. (b) Activation of the brain that occurred when the subjects attended to the areas indicated by the numbers on the stimulus. The center of each circle is the place on the brain that corresponds to the center of the stimulus. The yellow “hot spot” is the area of the brain that is maximally activated. Figure 6-14 p136

23 Womelsdorf (2006) showed that attention can cause a monkey’s receptive field to shift toward the place where the attention is directed. Figure 6.15 Receptive field maps on the retina determined when a monkey was attending to locations corresponding to (a) the small diamond and (b) the small circle. The yellow areas are areas of the receptive field that generate the largest response. Notice that the receptive field map shifts to the right when the monWomelsdorf (2006) – showed that attention can cause a monkey’s receptive field to shift toward the place where the attention is directed. key shifts its attention from the diamond to the circle. Figure 6-15 p137

24 Failure to detect superimposed images in a film
Gorillas in our midst: Sustained inattentional blindness (Simons & Chabris, 1999)

25

26 改變盲（change blindness ）
顯示視覺環境中只有一小部分是被表徵的 改變偵測作業 Change blindness blindness (Levin, 2000)

27 Figure 6.18 Stimulus for change blindness demonstration. See text.
Figure 6-18 p139

28 Figure 6.20 Stimulus for change blindness demonstration. See text.
Figure 6-20 p140

29 Figure 6.18 Stimulus for change blindness demonstration. See text.
Figure 6-18 p139

30 Figure 6.20 Stimulus for change blindness demonstration. See text.
Figure 6-20 p140

31 Figure 6. 19 Frames from a video that demonstrates change blindness
Figure 6.19 Frames from a video that demonstrates change blindness. The woman on the right is wearing a scarf around her neck in shots (a), (c), and (d), but not in shot (b). Also, the color of the plates changes from red in the first three frames to white in frame (d), and the hand position of the woman on the left changes between shots (c) and (d). Figure 6-19 p139

32 This slide can be used to finish up the topic of change blindness by noting that even though our visual experience is that our view of the world is sharp and in focus, in reality the periphery is not. We function quite well this way. Figure 6.13 (a) Scene with blur added to simulate the decrease in visual acuity that occurs in the periphery of the visual field. The fixation point is on the woman’s face. (b) The same scene without blur. Even though our ability to see details is poor in the periphery, we generally experience the world as being “sharp” rather than blurry. (Blurring courtesy of Stuart Anstis.)

33 The Distracting Effects of Task-Irrelevant Stimuli
與任務無關的刺激 Foster and Lavie (2008) Load theory of attention Perceptual capacity Perceptual load Low-load tasks

34 Figure 6.22 The task in Forster and Lavie’s (2008) experiment was to indicate the identity of a target (X or N) as quickly as possible. (a) The reaction time for the easy condition like the display on the left, in which the target is accompanied by small o’s, is faster than the reaction time for the hard condition, in which the target is accompanied by other letters. (b) Flashing a distracting cartoon character increases the reaction time for the easy task but has a smaller effect on the hard task. The increase for each task is indicated by the blue extensions of the bars. Figure 6-22 p141

35 Figure 6.23 The rationale for the idea that (a) low-load tasks that use few cognitive resources may leave resources available for processing unattended task-irrelevant stimuli, whereas (b) high-load tasks that use all of a person’s cognitive resources don’t leave any resources to process unattended task-irrelevant stimuli. Figure 6-23 p142

36 注意力對於特徵結合（binding）的促進
即便腦的不同分區處理不同的知覺層面，但主觀知覺經驗是統整的 Figure 6.24 Any stimulus, even one as simple as a rolling ball, activates a number of different areas of the cortex. Binding is the process by which these separated signals are combined to create a unified perception. Figure 6-24 p142

37 特徵整合論（feature integration theory）(Treisman & Gelade, 1980)
前注意（preattentive）階段分析視知覺的基本特徵，集中注意（focused attention）階段作特徵之整合以產生物體知覺 注意力像膠水般將what與where管道的訊息結合起來 Figure 6.25 Flow diagram of Treisman’s (1988) feature integration theory. Figure 6-25 p143

38 Binding需要集中注意力的證據 錯覺組合（illusory conjunction）(Treisman & Schmidt, 1982)
MASK 200 ms 受試報告數字及每個幾何圖形 18%機會產生錯覺組合—例如報告「小的紅色圓形」 產生錯覺組合的原因是因為在快速呈現下，受試的注意力被導向數字

39 Figure 6.27 Illustration of the idea that in the preattentive stage, an object’s features are “free floating.” Because they are not attached to a particular object, they can potentially become associated with any object in a display. When this happens, an illusory conjunction is created. Figure 6-27 p144

40 Figure 6.28 Stimuli used to show that top-down processing can reduce illusory conjunctions.
Figure 6-28 p144

41 視覺搜尋（visual search） Balint’s syndrome
RM頂葉受損，無法對個別物體產生集中注意力 即使呈現時間很長（10 s）仍產生高比例（23%）的錯覺組合 視覺搜尋（visual search） 特徵搜尋（feature search）vs. 組合搜尋（conjunction search） 組合搜尋需要注意力參與 RM無法進行組合搜尋? 正常人進行組合搜尋時頂葉會激發

42 Figure 6.29 Find the horizontal line in (a) and then the green horizontal line in (b). Which task took longer? Figure 6-29 p145

43 Binding在神經生理層次如何進行？--同步化假設（synchrony hypothesis）
皮質不同區域的神經元對同一物體屬性產生反應時，這些激發會同步化—以同樣型態（而非同時）產生激發 注意力增加同步化？ Needs more evidence

44 注意力的神經生理學 二個狀況下網膜影像均相同，只有注意力狀況的差別 促進神經元的激發（Colby et al., 1995）

45 這種促進作用在 V1就存在，但愈高階處理區域促進作用愈強

46 Figure 6.26: Top: scan path as a monkey looked for a target (the parrot on the roof). Just below picture: firing of an IT neuron as the monkey was looking. Bottom: graph showing how far the monkey’s gaze was from the parrot. Notice that the neuron begins firing just after the monkey has fixated on the parrot and shortly after this the monkey pulls the lever. Fig. 6-26, p. 137

47 Attention in Autism 自閉症患者對於社會互動的知覺與注意力歷程是不是出了問題？
Watched movie while eye fixations were tracked Autistic vs. Non-autistic people Autistic observers look at socially irrelevant stimuli in these situations. Figure 6.30 Where people look when viewing this image from the film Who’s Afraid of Virginia Woolf? Nonautistic viewers: white crosses; autistic viewers: black crosses Figure 6.31 Scan paths for nonautistic viewers (white path) and autistic viewers (black path) in response to the picture and dialogue while viewing this shot from Who’s Afraid of Virginia Woolf?

48 Neural Processes for Attention in Autism
Pelphrey et al. (2005) Observers pressed a button when they saw the character’s eyes moved. Accuracy Nonautistic = autistic Activation of the STS: Nonautistic ≠ autistic STS activities reflected expectation Autistic people cannot read intentions of others. Figure 6.32 (a) Observers in Pelphrey and coworkers’ (2005) experiment saw either the congruent condition, in which the animated character looked at the checkerboard 1 second after it appeared, or the incongruent condition, in which the character looked somewhere else 1 second after the checkerboard appeared. (b) Response of the STS in nonautistic and autistic observers to the two conditions. C = congruent; IC = incongruent.

49 Attention and Perceptual Completion
Perceptual completion is the perception of an object as extending behind occluding objects 習慣化(Habituation) – 刺激重複呈現，測量嬰兒的注視時間 去習慣化(dishabituation)：當刺激改變，嬰兒的注視時間增加

50 Figure 6. 33 Possible results of a habituation experiment
Figure 6.33 Possible results of a habituation experiment. See text for details. Figure 6-33 p147

51 Figure 6.34 (a) Stimulus used in the habituation phase of the Kellman and Spelke (1983) experiment. A rod moves back and forth behind a rectangular occluder. (b) Stimuli that are presented in the dishabituation phase of the experiment. Figure 6-34 p148

52 Figure 6-35 p148