prolonged practice: Herbert Simon and his students at Carnegie Mellon in the 1980s set the foundations for our understanding of expertise. For an excellent popular introduction to the subject, see Joshua Foer, Moonwalking with Einstein: The Art and Science of Remembering (New York: Penguin Press, 2011). He presents work that is reviewed in more technical detail in K. Anders Ericsson et al., eds., The Cambridge Handbook of Expertise and Expert Performance (New York: Cambridge University Press, 2006.)

kitchen was on fire: Gary A. Klein, Sources of Power (Cambridge, MA: MIT Press, 1999).

studied chess masters: Herbert Simon was one of the great scholars of the twentieth century, whose discoveries and inventions ranged from political science (where he began his career) to economics (in which he won a Nobel Prize) to computer science (in which he was a pioneer) and to psychology.

"The situation...recognition": Herbert A. Simon, "What Is an Explanation of Behavior?" Psychological Science 3 (1992): 15061.

affect heuristic: The concept of the affect heuristic was developed by Paul Slovic, a classmate of Amos's at Michigan and a lifelong friend.

without noticing the substitution:.1: The Characters of the Storyoffered many labels: For reviews of the field, see Jonathan St. B. T. Evans and Keith Frankish, eds., In Two Minds: Dual Processes and Beyond (New York: Oxford University Press, 2009); Jonathan St. B. T. Evans, "Dual-Processing Accounts of Reasoning, Judgment, and Social Cognition," Annual Review of Psychology 59 (2008): 25 {59 eight="0%"578. Among the pioneers are Seymour Epstein, Jonathan Evans, Steven Sloman, Keith Stanovich, and Richard West. I borrow the terms System 1 and System 2 from early writings of Stanovich and West that greatly influenced my thinking: Keith E. Stanovich and Richard F. West, "Individual Differences in Reasoning: Implications for the Rationality Debate," Behavioral and Brain Sciences 23 (2000): 64565.

subjective experience of agency: This sense of free will is sometimes illusory, as shown in Daniel M. Wegner, The Illusion of Conscious Will (Cambridge, MA: Bradford Books, 2003).

attention is totally focused elsewhere: Nilli Lavie, "Attention, Distraction and Cognitive Control Under Load," Current Directions in Psychological Science 19 (2010): 14348.

conflict between the two systems: In the classic Stroop task, you are shown a display of patches of different colors, or of words printed in various colors. Your task is to call out the names of the colors, ignoring the words. The task is extremely difficult when the colored words are themselves names of color (e.g., GREEN printed in red, followed by Y ELLOW printed in green, etc.).

psychopathic charm: Professor Hare wrote me to say, "Your teacher was right," March 16, 2011. Robert D. Hare, Without Conscience: The Disturbing World of the Psychopaths Among Us (New York: Guilford Press, 1999). Paul Babiak and Robert D. Hare, Snakes in Suits: When Psychopaths Go to Work (New York: Harper, 2007).

little people: Agents within the mind are called homunculi and are (quite properly) objects of professional derision.

space in your working memory: Alan D. Baddeley, "Working Memory: Looking Back and Looking Forward," Nature Reviews: Neuroscience 4 (2003): 82938. Alan D. Baddeley, Your Memory: A User's Guide (New York: Firefly Books, 2004).2: Attention and EffortAttention and Effort: Much of the material of this chapter draws on my Attention and Effort (1973). It is available for free download on my website (www.princeton.edu/~kahneman/docs/attention_and_effort/Attention_hi_quality.pdf). The main theme of that book is the idea of a limited ability to pay attention and exert mental effort. Attention and effort were considered general resources that could be used to support many mental tasks. The idea of general capacity is controversial, but it has been extended by other psychologists and neuroscientists, who found support for it in brain research. See Marcel A. Just and Patricia A. Carpenter, "A Capacity Theory of Comprehension: Individual Differences in Working Memory," Psychological Review 99 (1992): 12249; Marcel A. Just et al., "Neuroindices of Cognitive Workload: Neuroimaging, Pupillometric and Event-Related Potential Studies of Brain Work," Theoretical Issues in Ergonomics Science 4 (2003): 5688. There is also growing experimental evidence for general-purpose resources of attention, as in Evie Vergauwe et al., "Do Mental Processes Share a Domain-General Resource?" Psychological Science 21 (2010): 38490. There is imaging evidence that the mere anticipation of a high-effort task mobilizes activity in many areas of the brain, relative to a low-effort task of the same kind. Carsten N. Boehler et al., "Task-Load-Dependent Activation of Dopaminergic Midbrain Areas in the Absence of Reward," Journal of Neuroscience 31 (2011): 495561.

pupil of the eye: Eckhard H. Hess, "Attitude and Pupil Size," Scientific American 212 (1965): 4654.

on the subject's mind: The word subject reminds some people of subjugation and slavery, and the American Psychological Association enjoins us to use the more democratic participant. Unfortunately, the politically correct label is a mouthful, which occupies memory space and slows thinking. I will do my best to use participant whenever possible but will switch to subject when necessary.

heart rate increases: Daniel Kahneman et al., "Pupillary, Heart Rate, and Skin Resistance Changes During a Mental Task," Journal of Experimental Psychology 79 (1969): 16467.

rapidly flashing letters: Daniel Kahneman, Jackson Beatty, and Irwin Pollack, "Perceptual Deficit During a Mental Task," Science 15 (1967): 21819. We used a halfway mirror so that the observers saw the letters directly in front of them while facing the camera. In a control condition, the participants looked at the letter through a narrow aperture, to prevent any effect of the changing pupil size on their visual acuity. Their detection results showed the inverted-V pattern observed with other subjects.

Much like the electricity meter: Attempting to perform several tasks at once may run into difficulties of several kinds. For example, it is physically impossible to say two different things at exactly the same time, and it may be easier to combine an auditory and a visual task than to combine two visual or two auditory tasks. Prominent psychological theories have attempted to attribute all mutual interference between tasks to competition for separate mechanisms. See Alan D. Baddeley, Working Memory (New York: Oxford University Press, 1986). With practice, people's ability to multitask in specific ways may improve. However, the wide variety of very different tasks that interfere with each other supports the existence of a general resource of attention or effort that is necessary in many tasks.

Studies of the brain: Michael E. Smith, Linda K. McEvoy, and Alan Gevins, "Neurophysiological Indices of Strategy Development and Skill Acquisition," Cognitive Brain Research 7 (1999): 389404. Alan Gevins et al., "High-Resolution EEG Mapping of Cortical Activation Related to Working Memory: Effects of Task Difficulty, Type of Processing and Practice," Cerebral Cortex 7 (1997): 37485.

less effort to solve the same problems: For example, Sylvia K. Ahern and Jackson Beatty showed that individuals who scored higher on the SAT showed smaller pupillary dilations than low scorers in responding to the same task. "Physiological Signs of Information Processing Vary with Intelligence," Science 205 (1979): 128992.

"law of least effort": Wouter Kool et {ute979): 1289al., "Decision Making and the Avoidance of Cognitive Demand," Journal of Experimental Psychology-General 139 (2010): 66582. Joseph T. McGuire and Matthew M. Botvinick, "The Impact of Anticipated Demand on Attention and Behavioral Choice," in Effortless Attention, ed. Brian Bruya (Cambridge, MA: Bradford Books, 2010), 10320.

balance of benefits and costs: Neuroscientists have identified a region of the brain that assesses the overall value of an action when it is completed. The effort that was invested counts as a cost in this neural computation. Joseph T. McGuire and Matthew M. Botvinick, "Prefrontal Cortex, Cognitive Control, and the Registration of Decision Costs," PNAS 107 (2010): 792226.

read distracting words: Bruno Laeng et al., "Pupillary Stroop Effects," Cognitive Processing 12 (2011): 1321.

associate with intelligence: Michael I. Posner and Mary K. Rothbart, "Research on Attention Networks as a Model for the Integration of Psychological Science," Annual Review of Psychology 58 (2007): 123. John Duncan et al., "A Neural Basis for General Intelligence," Science 289 (2000): 45760.

under time pressure: Stephen Monsell, "Task Switching," Trends in Cognitive Sciences 7 (2003): 13440.

working memory: Baddeley, Working Memory.

tests of general intelligence: Andrew A. Conway, Michael J. Kane, and Randall W. Engle, "Working Memory Capacity and Its Relation to General Intelligence," Trends in Cognitive Sciences 7 (2003): 54752.

Israeli Air Force pilots: Daniel Kahneman, Rachel Ben-Ishai, and Michael Lotan, "Relation of a Test of Attention to Road Accidents," Journal of Applied Psychology 58 (1973): 11315. Daniel Gopher, "A Selective Attention Test as a Predictor of Success in Flight Training," Human Factors 24 (1982): 17383.3: The Lazy Controller"optimal experience": Mihaly Csikszentmihalyi, Flow: The Psychology of Optimal Experience (New York: Harper, 1990).

sweet tooth: Baba Shiv and Alexander Fedorikhin, "Heart and Mind in Conflict: The Interplay of Affect and Cognition in Consumer Decision Making," Journal of Consumer Research 26 (1999): 27892. Malte Friese, Wilhelm Hofmann, and Michaela Wanke, "When Impulses Take Over: Moderated Predictive Validity of Implicit and Explicit Attitude Measures in Predicting Food Choice and Consumption Behaviour," British Journal of Social Psychology 47 (2008): 397419.

cognitively busy: Daniel T. Gilbert, "How Mental Systems Believe," American Psychologist 46 (1991): 10719. C. Neil Macrae and Galen V. Bodenhausen, "Social Cognition: Thinking Categorically about Others," Annual Review of Psychology 51 (2000): 93120.

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