Estructura del Modelo de Reconstrucción de la Experiencia

we read a paragraph with a surprise ending, we make a larger number of regression

movements as we reread the puzzling passage (Underwood & Batt, 1996). In summary, the research shows that a wide variety of cognitive factors have an important influence on the pattern and speed of our saccadic eye movements (McDonald & Shillcock, 2003; Reichle et al., 1998). Saccadic eye movements clearly help us become more active, flexible readers (Findlay & Gilchrist, 2001).

Section Summary:

Three Kinds of Attention Processes

1. Attention is a concentration of mental activity, and it allows our cognitive processes to take in limited portions of our environment and our memory. 2. The first kind of attention process discussed in this chapter is divided attention.

Research on divided attention shows that performance often suffers when people must attend to several stimuli simultaneously. For example, we cannot talk on a hands-free cell phone and drive carefully at the same time. However, with exten- sive practice, people’s performance on some divided-attention tasks can improve. 3. The second kind of attention process is selective attention, and the chapter

inspects three different examples of selective attention.

a. The first example of selective attention is the dichotic listening technique, which shows that we typically notice little about an irrelevant message. Occa- sionally, however, we may notice the gender of the speaker, our own name, or some semantic aspects of the irrelevant message.

b. A second example of a selective-attention task is the Stroop effect. A variant called the “emotional Stroop task” demonstrates that people with certain dis- orders have difficulty identifying the ink color of words relevant to their disor- der; for example, people with eating disorders take longer than other people to report the ink color of words related to food.

c. A third example of selected-attention findings is visual search. For example, we can locate a target faster if it appears frequently, if it differs from irrelevant objects on only one dimension (e.g., color), and if a specific feature of a stimu- lus (e.g., a line) is present rather than absent.

4. The final kind of attention process is saccadic eye movements, which our visual system makes during reading. Saccadic-movement patterns depend on factors such as the predictability of the text, individual differences in reading skill, and the more general meaning of the text.

EXPLANATIONS FOR ATTENTION

So far, this chapter has examined three attention processes that help us regulate how much information we take in from our visual and auditory environment. Specifically, we have difficulty paying attention to two or more messages at one time (divided atten- tion). In addition, when we are paying attention to one message, we have difficulty notic- ing information about irrelevant messages (selective attention). Furthermore, our saccadic

eye movements regulate the way our eyes move in order to acquire information. Researchers have tried to account for these components of attention by conducting neu- roscience studies and by devising theories to explain the characteristics of attention.

Neuroscience Research on Attention

During recent decades, researchers have developed a variety of sophisticated techniques for examining the biological basis of behavior; we introduced many of these approaches in Chapter 1. Research using these techniques has identified a network of areas throughout the brain that accomplish various attention tasks (Farah, 2000a; Posner & Rothbart, 2007b). Several regions of the brain are responsible for attention, including some struc- tures that are below the surface of the cerebral cortex (Just et al., 2001; Posner & Rothbart, 2007b). For example, several brain structures beneath your own cortex are now coordinating their actions so that your eye can leap forward in saccadic move- ments until you reach the end of this sentence (Schall, 2004). In this discussion, how- ever, we’ll focus on structures in the cerebral cortex, as shown in Figure 3.2. Take a moment to compare Figure 3.2 with Figure 2.1 (p. 35), which showed the regions of the cortex that are most relevant in object recognition.

FIGURE 3.2

A Schematic Drawing of the Cerebral Cortex, as Seen from the Left Side, Showing the Four Lobes of the Brain and the Regions That Are Most Important on Attention Tasks.

Temporal lobe Frontal lobe Parietal lobe Occipital lobe Orienting Attention Network Executive Attention Network

Explanations for Attention 79 Michael Posner and Mary Rothbart (2007a, 2007b) propose that three systems in

the cortex manage different aspects of attention: (1) the orienting attention network, (2) the executive attention network, and (3) the alerting attention network. This third system, the alerting attention network, is responsible for making you sensitive and alert to new stimuli; it also helps to keep you alert and vigilant for long periods of time (Posner & Rothbart, 2007a, 2007b). Because this chapter has not examined the alerting component of attention, we will focus instead on the other two systems, the orienting attention network and the executive attention network.

The Orienting Attention Network. Imagine that you are searching the area around a bathroom sink for a lost contact lens. When you are selecting information from sen- sory input, your orienting attention network is activated. The orienting attention network is responsible for the kind of attention required for visual search, in which you must shift your attention around to various spatial locations (Chun & Wolfe, 2001; Luck & Vecera, 2002; Posner & Rothbart, 2007b). According to Posner and Rothbart (2007a), the orienting network develops during the first year of life. Figure 3.2 shows that two important components of the orienting attention network are located in the parietal lobe of the cortex.

How did researchers identify the parietal cortex as the region of the brain used in attention tasks related to visual searches? Several decades ago, the only clue to the organization of the brain was provided by people with brain lesions (Posner, 2004). The term brain lesion refers to specific brain damage caused by strokes, accidents, or other traumas. People who have brain damage in the parietal region of the right hemi- sphere of the brain have trouble noticing a visual stimulus that appears on the left side of their visual field. In contrast, people with damage in the left parietal region have trouble noticing a visual stimulus on the right side (Luck & Vecera, 2002; Posner & DiGirolamo, 2000a; Styles, 2005).

The lesions produce unusual deficits. For instance, a woman with a lesion in the left parietal region may have trouble noticing the food on the right side of her plate. She may eat only the food on the left side of her plate, and she might even complain that she didn’t receive enough food (Farah, 2000a; Humphreys & Riddoch, 2001). Amazingly, however, she may not seem to be aware of her deficit.

Part A of Figure 3.3 shows a simple figure—a clock—that was presented to a man with a lesion in the right parietal lobe. He was asked to copy this sketch, and Part B shows the figure he drew. Notice that the left part of the drawing is almost completely missing. The drawing demonstrates that this man is experiencing unilateral neglect, defined as a spatial deficit for one half of the visual field.

Much of the more recent research on the orienting attention network has used positron emission tomography (PET scan), in which researchers measure blood flow in the brain by injecting the participant with a radioactive chemical just before he or she performs a cognitive task. As discussed in Chapter 1, this chemical travels through the blood to the parts of the brain that are active during the cognitive task. A special camera makes an image of the accumulated chemical. According to PET-scan research, the parietal cortex shows increased blood flow when people perform visual searches and pay attention to spatial locations (e.g., Palmer, 1999; Posner & Rothbart, 2007b).

The Executive Attention Network. The Stroop task that you tried in Demon- stration 3.1 relied primarily on your executive attention network. The executive attention network handles the kind of attention we use when a task features conflict (Posner & Rothbart, 2007a, 2007b). On the Stroop task, for example, you need to inhibit your automatic response of reading a word, in order to name the color of the ink (Fan et al., 2002). The executive attention network is responsible for inhibiting your automatic responses to stimuli (Stuss et al., 2002). As you can see in Figure 3.2, the prefrontal portion of the cortex is the region of your brain where the executive attention network is especially active.

The executive attention network also operates when people are asked to listen to a list of nouns and to state the use of each word, such as listening to the word needle and responding “sew” (Posner & DiGirolamo, 2000a). Furthermore, the executive atten- tion network is active for top-down control of attention (Farah, 2000a). The executive attention network begins to develop at about age 2, much later than the orienting atten- tion network (Posner & Rothbart, 2007a).

Posner and Rothbart (2007b) argue that the executive attention network is extremely important when you acquire academic skills in school, for example, when you learned to read. Executive attention also helps you learn new ideas (Posner & Roth- bart, 2007a). For example, as you are reading this passage, your executive attention net- work has been actively taking in new information and—ideally—comparing this network with the orienting attention network. This process of reading and understanding a college-level textbook is challenging. Not surprisingly, the location of the executive attention network overlaps with the areas of your brain that are related to general intel- ligence (Duncan et al., 2000; Posner & Rothbart, 2007b).

FIGURE 3.3

The Original Figure (A) Presented to a Man with a Lesion in the Right Parietal Lobe, and the Figure He Drew (B).

12 7 8 9 10 11 2 3 1 4 5 6 A B

Explanations for Attention 81 In summary, PET scans and other neuroscience techniques have identified one

brain region that is active when we are searching for objects (the orienting attention net- work). These techniques also show that a different brain region is active when we must inhibit an automatic response and produce a less obvious response (the executive atten- tion network); this second network is also active in academic learning.