Consciousness and the Social Brain by Michael S. A. Graziano Page A
Authors: Michael S. A. Graziano
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look disproportionately more at the eyes, as though seeking information from that facial feature. 8 People are excellent at detecting even tiny changes in someone’s gaze direction. 9 We are experts at watching other people’s eyes and extracting information from eyes.
A possible brain mechanism for social attention was discovered in the 1980s by Perrett and colleagues. 3 They were studying the monkey brain, monitoring the activity of neurons in a region of the cortex called the superior temporal sulcus (STS). The animal was shown pictures of eyes. Some neurons became active in response to pictures of eyes that looked to the left, others to pictures of eyes that looked to the right. A special machinery in the monkey brain seemed to be dedicated to the task of tracking someone else’s gaze.
Further experiments using human volunteers in a brain scanner showed that the human brain also contained a specialized machinery for tracking someone else’s gaze. 2 , 4 , 5 , 10
The idea of social attention was elaborated by many scientists. One of the more interesting accounts was proposed in 1995 by Baron-Cohen. 1 In his account, the ability to reconstruct someoneelse’s thoughts begins with the EDD as he called it, the eye direction detector. The EDD provides crucial information to other proposed modules in the brain, including the intentionality detector and the theory of mind mechanism. One of his more influential proposals was the shared attention mechanism. This proposed mechanism detects when you and someone else near you are paying attention to the same thing. It is radar for social alignment.
But do we really align our attention with other people’s? Do we have a natural herd instinct when it comes to attention, pointing our eyes collectively at the same thing as a means of social cohesion or social communication?
Posner introduced a now famous task for studying human attention. 11 In that task, which is diagrammed in Figure 7.3A , you look at the center of a display screen. At an unpredictable time a small spot, the target, appears either to the left or the right. As soon as the target appears, you must press a button as quickly as possible. Sometimes the location of the target is precued. A square is briefly flashed on the screen, and then shortly thereafter the target appears at that same location. In these cases, your reaction time is significantly faster. Your spatial attention has been directed by the cue to the correct location, speeding up your processing of the target spot. In contrast, sometimes the cue is presented on one side and then, shortly thereafter, the target is presented on the opposite side. In those cases, your reaction time is slower. Your spatial attention has been diverted by the cue to the wrong side, thereby slowing your ability to detect the target. This elegant paradigm has become a staple method to study spatial attention.
Friesen and Kingstone 12 used a clever modification of the task, diagrammed in Figure 7.3B . In this task, you look at a drawing of a face in the center of a display screen. The eyes on the face may suddenly look to the left or to the right. A fraction of a second later a target spot appears either to the left or to the right. Your task is to press a button as quickly as possible to indicate the appearance of the target stimulus. In this paradigm, the direction of gaze of the central face acts as an attentional cue. When the face looks to the left and the target then appears on the left, your reaction time is shorter, indicating that your attention followed the face’s gaze shift to the left. When the face looks to the right and then the target appears on the left, your reaction time is longer, indicating that your attention initially followed the face’s gaze shift to the right and then had to shift back to the target on the left.
FIGURE 7.3
Testing visual attention with the Posner task. (A) In the standard version, a person looks at the central cross. Then a
A possible brain mechanism for social attention was discovered in the 1980s by Perrett and colleagues. 3 They were studying the monkey brain, monitoring the activity of neurons in a region of the cortex called the superior temporal sulcus (STS). The animal was shown pictures of eyes. Some neurons became active in response to pictures of eyes that looked to the left, others to pictures of eyes that looked to the right. A special machinery in the monkey brain seemed to be dedicated to the task of tracking someone else’s gaze.
Further experiments using human volunteers in a brain scanner showed that the human brain also contained a specialized machinery for tracking someone else’s gaze. 2 , 4 , 5 , 10
The idea of social attention was elaborated by many scientists. One of the more interesting accounts was proposed in 1995 by Baron-Cohen. 1 In his account, the ability to reconstruct someoneelse’s thoughts begins with the EDD as he called it, the eye direction detector. The EDD provides crucial information to other proposed modules in the brain, including the intentionality detector and the theory of mind mechanism. One of his more influential proposals was the shared attention mechanism. This proposed mechanism detects when you and someone else near you are paying attention to the same thing. It is radar for social alignment.
But do we really align our attention with other people’s? Do we have a natural herd instinct when it comes to attention, pointing our eyes collectively at the same thing as a means of social cohesion or social communication?
Posner introduced a now famous task for studying human attention. 11 In that task, which is diagrammed in Figure 7.3A , you look at the center of a display screen. At an unpredictable time a small spot, the target, appears either to the left or the right. As soon as the target appears, you must press a button as quickly as possible. Sometimes the location of the target is precued. A square is briefly flashed on the screen, and then shortly thereafter the target appears at that same location. In these cases, your reaction time is significantly faster. Your spatial attention has been directed by the cue to the correct location, speeding up your processing of the target spot. In contrast, sometimes the cue is presented on one side and then, shortly thereafter, the target is presented on the opposite side. In those cases, your reaction time is slower. Your spatial attention has been diverted by the cue to the wrong side, thereby slowing your ability to detect the target. This elegant paradigm has become a staple method to study spatial attention.
Friesen and Kingstone 12 used a clever modification of the task, diagrammed in Figure 7.3B . In this task, you look at a drawing of a face in the center of a display screen. The eyes on the face may suddenly look to the left or to the right. A fraction of a second later a target spot appears either to the left or to the right. Your task is to press a button as quickly as possible to indicate the appearance of the target stimulus. In this paradigm, the direction of gaze of the central face acts as an attentional cue. When the face looks to the left and the target then appears on the left, your reaction time is shorter, indicating that your attention followed the face’s gaze shift to the left. When the face looks to the right and then the target appears on the left, your reaction time is longer, indicating that your attention initially followed the face’s gaze shift to the right and then had to shift back to the target on the left.
FIGURE 7.3
Testing visual attention with the Posner task. (A) In the standard version, a person looks at the central cross. Then a
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