Emotions Measure Problems and Motivate Responses, but Their Prompts Can Misfire

An emotion can tell you what your mind is treating as important without telling you what to do next. Envy may direct attention toward someone else’s success; anger may prepare you to deter a threat. But the person you envy may not be a useful model, and the person who angered you may be gone for good. For psychologist Robert Kurzban, that gap between a feeling’s signal and the action it urges is where an evolutionary understanding can become practically useful.

Kurzban describes emotions as systems that measure something relevant and motivate a response. Hunger registers a need for food and moves someone to eat; jealousy registers a possible threat to a relationship and can prompt someone to check what is happening. The measurement may be simple, as with thirst, or involve a complicated judgment about another person, as in admiration or envy. Either way, information matters to an organism only if it can affect what the organism does.

The evolutionary perspective, in Kurzban’s account, asks what a brain with a particular feeling is equipped to do. Humans are animals with an evolutionary history; the question is not only what a feeling is like but what problem it may address. His framework is meant to apply across bodily sensations and social emotions: each registers something, then helps direct behavior.

That approach also offers one possible explanation for why feelings have subjective force. A person can be hungry, afraid, curious and tired at once, with each state making competing claims on attention and action. How should fear of a bear compare with hunger for food nearby? Kurzban suggests that consciousness may serve as a kind of common currency—a way of weighing unlike motivations and bringing one to the front. A thermometer has a single task; a person has many. He presents this as a possibility, not a settled account of why experience feels like anything at all.

The unpleasantness of some feelings may help make their motivational force effective. Kurzban points to people who do not feel pain, or do not feel the urge to escape it: they can fail to respond to injury and may not live long. If a hand in a fire did not feel bad, there would be less reason to pull it away. In this sense, the aversive quality of a feeling is part of how it gets behavior changed.

But the signal and the suggested action are not the same thing. Kurzban’s practical question is what a feeling is trying to get someone to do, and whether that action fits the situation they are actually in. Understanding a feeling does not make it disappear. It can create a moment to decide whether to follow it.

That distinction matters when a system built for one setting operates in another. Kurzban uses envy to illustrate the problem. In a small social world, another person’s success might have been a relevant comparison or a realistic opportunity to pursue. Social platforms expose people to far more lives and achievements than they can reasonably use as guides. The envy system can be pushed into overdrive, urging someone to compete for an outcome that may be neither attainable nor worth pursuing.

Anger can be similarly out of place. In a setting where a person who wronged you was likely to appear again, anger might help deter a repeat offense. A driver who cuts you off, however, may disappear from your life moments later. The anger can still arrive, but the action it once supported may have no useful target. Recognizing what anger is prompting—deterrence—makes it possible to ask whether deterrence is still relevant.

Kurzban’s examples do not require treating every feeling as a reliable reading of the present. Envy may still be registering comparison, and anger may still be registering an offense. The question is whether that comparison or offense should determine what happens next.

Many bodily feelings, Kurzban argues, are protective systems built around threats such as parasites and toxins. Their functions can be easier to see in physical sensations than in social emotions: the signal and the action it prompts are closely connected.

Itch, for example, can draw attention to something on the skin that may be crawling, biting or laying eggs. The sensation is not pain, but it can become difficult to ignore. Williamson describes trying to resist an itch on a plane and finding that it can crowd out other thoughts. Kurzban adds that itchiness can spread socially: hearing people talk about itching may make a listener feel itchy too. He offers a tentative explanation: if other people are scratching, there may be irritants nearby that you have not noticed, so the reaction might prompt greater vigilance.

Some feelings resist a neat explanation. Kurzban calls yawning a difficult case: other animals yawn, yawning can spread socially, and one proposed function is to take in more oxygen. He also mentions a paper that listed many possible explanations, and says the research on individual feelings can be surprisingly sparse. Some sensations remain open questions.

Pooping is a more straightforward example of a bodily system that measures a condition and prompts a response. Pressure in the intestinal tract increases as waste builds up; that pressure helps produce the urge to go, followed by the release of a valve. The system also has to regulate when and where the act happens. Kurzban notes that pooping can leave evidence and that waste can attract parasites. He describes latrine behavior—animals defecating away from their group—and notes that some animals bury their waste. These behaviors illustrate that defecation is not only a matter of sensing when to go; where an animal goes can matter too.

Nausea and vomiting are another possible defense. Kurzban says vomiting can expel parasites or toxins without forcing them through the rest of the digestive tract. One proposed explanation for motion sickness connects it to a mismatch between what the eyes report and what the body’s balance system reports. Since toxins and parasites can affect balance, that disagreement between senses might be interpreted as evidence that something harmful has been ingested, prompting the body to get rid of it. Kurzban says this hypothesis might not be true.

Williamson’s story about falling ill on New Year’s Eve shows how bodily information may arrive in stages and how difficult it can be to identify its source. He had been in contact with a business partner whose family had a stomach bug. While managing a sold-out event in Manchester, Williamson noticed he was short-tempered with people around him. He paused to ask himself why he was being a “dick,” then began to feel hot and sweaty, followed by a cold sensation in his stomach. Only then did he connect those changes with the illness in his partner’s household. He tried to hold out until he got home, but became sick as soon as he arrived.

Kurzban picks up the contrast between the feeling and its apparent cause. A person can notice irritability, unease or fear without knowing whether the source is illness, a social problem or something else. He recalls feeling afraid in a canyon, with a possible explanation in the ancient risk of being in low ground where others could see you but you could not easily see them. The present-day setting may be a national forest, but the feeling can still arise.

Disgust, in Kurzban’s account, may estimate pathogen risk and motivate distance from likely sources. Feces and decaying flesh are examples: their cues can indicate the presence of organisms that may harm us. Disgust can prompt someone to move away, remove a contaminant from the body or avoid putting it in the mouth. Kurzban links the facial expression of disgust to expulsion: the tongue and other movements can resemble pushing something out.

Sexual disgust raises a different question: why would a person reject a sexual opportunity? Kurzban points to one proposed answer in the Westermarck effect. People who grow up together can find the idea of sex with each other repellent, even when they are not genetically related. He refers to research by Deb Lieberman and to children raised together in Israeli kibbutzim. The discussion’s point is that early proximity and shared upbringing may cue sexual aversion.

Williamson says that, as an only child, he can understand the idea of incest disgust but cannot summon the feeling from personal experience. Kurzban compares the development of some emotional responses to language: people may acquire a response when they grow up with the relevant cues, just as they acquire a language from their environment. He offers his own example of lacking a visceral response to someone using drugs in private, despite recognizing that drug use can cause social problems. The exchange illustrates how people can differ in which emotional responses feel immediate, and how an individual’s experience may depend on what cues they encountered.

Individual differences complicate any simple idea of a single, optimal emotional setting. Kurzban describes claustrophobia through “prospect and refuge”: being able to see what is coming and to escape. A closed, dark space removes both. An expansive view can offer prospect by making it easier to see what is nearby, which may help explain why people often find open landscapes attractive. Kurzban recounts his own late-onset claustrophobia, discovered inside a cave.

Williamson suggests that a group would not benefit if every member had the same fear, caution or willingness to experiment: if everyone avoided closed spaces, no one might enter the cave. Kurzban sees a related possibility in personality variation. Some people may be adventurous where others are cautious, and the group may retain variation in those tendencies.

Kurzban describes anxiety as fear directed toward the future. It can help a person anticipate danger, assess how likely it is and prepare a response. Before public speaking, for example, anxiety may lead someone to consider what questions could arise or how to present themselves. A certain amount of vigilance can support planning; too much can become paralyzing.

Anxiety also has costs. Kurzban invokes opportunity cost: time spent anticipating one threat is time not spent on something else. Thinking about a podcast for years before appearing on it could make someone more prepared, but it would also consume years of life. Anxiety has to compete with other demands rather than simply increase without limit.

The modern environment may prompt some responses beyond their original range. Kurzban points to social media and the sense of being continuously observed. For a social species, reputation matters, and a world where actions are broadcast can make vigilance about how others see us feel more pressing. He is cautious about strong claims concerning recent social-media trends. Williamson says findings surrounding the “Anxious Generation” thesis seemed to be repeatedly confirmed and challenged; Kurzban agrees that it is fair to wait and see how the evidence develops.

Panic may work differently from anxiety. Kurzban describes a fish trapped in a net that flops randomly until it lands back in the water. The fish does not appear to have a plan; it moves because movement is the remaining option. He suggests panic may occur when the system registers that failing to act could lead to catastrophe, leaving movement—sometimes disorderly movement—as the available response.

He extends the idea to a military rout. In the example he discusses, one side appears to be losing and soldiers on that side run for the ships rather than retreat in an orderly way. That disorder can be bad for the group, but for an individual soldier facing the worst possible outcome, immediate flight may seem like the best remaining choice. Kurzban’s point is that panic may arise when someone perceives that doing nothing is dangerous and the options have narrowed.

The modern setting can also make it hard to know what a feeling is responding to. Someone may know that a city is generally safe and still feel background anxiety around strangers. Kurzban says he experiences some such anxiety walking around Philadelphia, where he is surrounded by people he does not know. The feeling need not be a considered conclusion that each stranger is dangerous; it can be a response to a social environment that differs from the one in which the emotional system developed.

Kurzban sees some aesthetic preferences as responses to things correlated with fitness or opportunity. People may like a landscape that offers a good view, or be drawn to signs of health in a body. The attractive appearance of food can focus attention on an opportunity to eat. He describes these reactions as guides toward something potentially beneficial, while acknowledging that aesthetics are complicated.

Aesthetic pleasure may differ from direct sensory pleasure in its level of abstraction. Being petted is a concrete sensation; the shape of a beautiful play or a landscape is more complex. Still, Kurzban sees a possible common thread: both can make something attractive because it is associated with a good opportunity. A ripe apple, for example, can look appealing and draw someone’s attention toward eating it.

Grooming can combine sensory reward with social information. Kurzban suggests that gentle touch from someone who could hurt you but chooses not to may be a signal of alliance. Grooming may have begun with removing insects or dirt, but among humans, gentle touch can also indicate affiliation. Williamson brings up work on the speed and pressure of pleasant touch and reads aloud an on-air summary of findings he says he recalled from previous research. In that summary, pleasantness rises and then falls across different stroking speeds, with gentle stroking around three centimeters per second described as near the peak. He also describes light pressure as more pleasant than hard pressure.

Kurzban responds by pointing to the reported correspondence, in Williamson’s summary, between touch-sensitive nerve activity and subjective pleasantness. He sees this as a clear example of a bodily measurement being linked to conscious experience. Williamson offers an adaptive explanation for gentle touch: it may have a role in social bonding and caregiving, because people use that kind of stroking when comforting a partner or child. He connects this idea to infant-directed and animal-directed speech, which Kurzban says can share frequencies and intonations.

Spicy food offers an example of pleasure with a threshold. Kurzban compares it to a roller coaster: a little intensity can be enjoyable, but beyond a point the experience becomes unpleasant or painful. He says spices may help suppress pathogens in food, and refers to work suggesting that places with warmer, wetter conditions and more parasites used more spices, controlling for the spices available. He qualifies the account, noting the uncertainty around older psychological findings. His explanation is that plants use chemical defenses against pathogens and people can use those chemicals in food; the taste may be beneficial up to the point where it becomes too intense.

Williamson describes a sauce that was both sweet and unusually hot. He enjoyed the taste, but the heat later caused pain. Kurzban’s response is that pain signals possible damage and can discourage repeating an experience. Taste can make someone continue eating even when the body’s warning system eventually says the cost is too high.

Fun may reward activity that lets people practice. Kurzban suggests that games and play provide a relatively safe setting to learn skills that matter elsewhere. Children playing team sports might be rehearsing coordination useful for hunting or conflict. If play supports learning, pleasure can encourage people to keep doing it before the stakes are real. He finds dancing harder to explain: people coordinate their movements to music, but the activity does not clearly rehearse a practical task.

Music itself may also function as a signal. Kurzban describes Geoffrey Miller’s argument that creating music can demonstrate intelligence, creativity and taste—capacities that may be difficult to fake. The strong reactions audiences have to performers could reflect the importance of mate assessment, he suggests. He compares this with pornography and other intense stimuli that can activate systems beyond the scale of the ordinary cues they would have encountered.

The discussion of sexual stimulation makes the measurement point concrete. Williamson recounts what he says a psychiatrist had told him about some men becoming accustomed to a level of pressure during masturbation that a partner’s body may not reproduce. Kurzban treats the example as a mismatch between the cues the system responds to and the circumstances it is meant to navigate.

Envy and jealousy register different social problems in Kurzban’s account. Envy directs attention toward someone doing better in some domain and can prompt imitation or competition. Jealousy concerns a possible threat to a relationship, whether romantic or friendly, and can prompt efforts to protect the relationship. Envy is more about a perceived opportunity; jealousy is more about defense.

That distinction does not make envy pleasant or jealousy admirable. Someone else’s success may offer a model to learn from, while the comparison can also make a person dissatisfied with what they have. Online exposure magnifies the problem by making distant people’s achievements part of the everyday comparison set. Kurzban’s example is the person who sees others with more success, friends or status and feels pushed to pursue what they have, even if that pursuit is unrealistic or not in their own interest.

Jealousy can protect a relationship but can also be embarrassing to admit. Williamson asks why it feels so bad if evolution preserved it. Kurzban speculates that describing jealousy as pathological may sometimes serve the interests of someone who benefits when another person lowers their guard. He uses the image of a person saying jealousy is irrational while taking advantage of another person’s reduced vigilance. This is a possible strategic use of moral language, not an argument that jealousy is always justified.

For Kurzban, one of the most damaging modern expressions of these social systems is the appetite for moral condemnation. He suggests that people can benefit from joining a group that accuses someone else: it may draw attention away from them, remove a competitor or put them on the side of a larger coalition. In contemporary life, social media makes it easy to indulge this appetite. He compares it to food environments that make sugar, fat and salt readily available: a system that responds to an opportunity can be activated repeatedly when the environment supplies the cue.

Williamson brings up a person who was mistaken for the journalist Andy Ngo and confronted by protesters. In the clip they watch, the person repeatedly asks why he is being targeted and whether the protesters think he is Ngo. Kurzban notes that the person also describes the confrontation as racist. His point is that moral accusation can generate another moral accusation in response, with each side treating its own charge as decisive.

Kurzban likens public attacks to moral roulette. People may be attacking someone who did something wrong, but they may also have the wrong person. He refers to a news story about someone served papers after being mistaken for a different person and then receiving doxxing and death threats. Williamson’s example makes the risk more immediate: even when the target says the identification is wrong, the group may continue to treat the accusation as proof of guilt.

The same framework can make morally uncomfortable emotions easier to study without endorsing them. Williamson argues that an evolutionary explanation is not a justification: understanding why a response may have developed does not establish that the response is good. Kurzban agrees that people often confuse explaining a behavior with condoning it. He says this can make researchers hesitant to study topics involving sex and race, which he considers especially sensitive.

For Kurzban, that hesitation can also undermine attempts to change behavior. If someone steals to obtain a valuable object, securing the object addresses a different problem from an intervention aimed at someone who steals to assert power over another person. Understanding motives does not guarantee an effective solution, but it can help identify what kind of solution to try.

Kurzban argues that emotions look like evolved systems because they recur across people and across time, and because their components appear suited to the problems they address. He points to jealousy and envy in ancient literature as well as contemporary life. The consistency of these feelings is part of the case he makes; it does not, by itself, establish a particular evolutionary account.

He rejects the idea that an evolutionary explanation is automatically a “just-so story.” For him, an explanation is a hypothesis that can be tested. The relevant evidence is not necessarily a direct account of what happened millions of years ago; it can be evidence about the design of a present-day mechanism. The eye’s structure supports the claim that it is adapted for seeing. Similarly, features of hunger—what it registers and how it changes behavior—can support a hypothesis about its function. Evolutionary theory helps generate the hypothesis; researchers must still test it.

Kurzban says he put the sources for his work online so readers could examine the evidence he uses for particular feelings. He argues that evolutionary reasoning can guide the development of a hypothesis about function, but that the hypothesis should then be assessed against evidence. A compelling story is not enough.

The confidence warranted by one account may not carry over to another. Kurzban calls yawning a hard case, says the motion-sickness hypothesis might not be true, and marks his accounts of claustrophobia, grooming and panic as possibilities. His depression explanation is also a proposal rather than a settled account. The measure-and-motivate framework gives him a way to ask what a sensation does; it does not mean that all proposed answers are equally supported.

Friendship, in Kurzban’s account, is more than pleasant company. People invest in friends who can support them, exchange help, play and coordinate. An important feature of human friendship, he argues, is that people rank their friends, even if they do not announce the ranking. Knowing where one stands in another person’s “queue” can be useful when a conflict breaks out: it offers a clue about who may be willing to take whose side, not a guarantee of what anyone will do.

This alliance function helps explain why friendship can be both supportive and vulnerable to rivalry. A friend may be an ally in one context and a competitor in another. Kurzban describes jealousy among friends as an understudied feeling: if a friend starts spending time with someone else, a person may worry about being demoted in the friendship order. He remembers children bargaining over who would be whose best friend. Williamson suggests that the feeling might be stronger in children because they have less ability to look after themselves; Kurzban adds that children may also be less inhibited and strategic about expressing it.

Friendship need not be restricted to kin. Kurzban points to chimpanzees forming alliances with non-kin members of their communities and to long-term associations among male dolphins. He notes that the function of those dolphin associations is mating-related, and the exchange makes the broader point: relationships called friendship can serve different functions in different species. For humans, he emphasizes mutual support, exchange, play and alliance.

Kurzban also describes hatred as more persistent than anger. Anger can arise over a local offense and fade after an apology; hatred may reflect a judgment that someone repeatedly threatens you and should be kept from doing harm. The response may be to avoid or neutralize that person, though the ways this plays out in a modern setting differ from those available in ancestral environments. The distinction is not just a difference in intensity: anger can be temporary, while hatred implies a more enduring view of the person and the relationship.

Contempt and resentment register different social judgments. Contempt treats a person as not worth affiliating with, given limited time and social capacity, and tends to motivate avoidance. Resentment is more focused on an act or allocation: someone received a benefit, such as a promotion, that the resentful person believes they did not deserve. Kurzban suggests resentment may prompt someone to publicize the alleged unfairness and recruit others to challenge it.

Empathy is also information, not necessarily kindness. Kurzban describes it as a way of estimating what another person is feeling and, in turn, what their own emotional system is registering. That information can help someone comfort a friend, but it can also help someone hurt an adversary. Knowing what will distress another person is useful for both care and harm; the moral character of the action depends on how the information is used.

Williamson asks whether empathy can work like investment advice: a person may help someone who is likely to appreciate or repay the help. Kurzban accepts that reciprocity may be part of the calculation. He uses a drowning person as an example: if helping costs little and saves someone, the benefit can be substantial. But people may be less inclined to help someone they believe cannot repay them. He compares this to the “banker’s paradox”: lending makes most sense when someone needs help but can repay it.

Gratitude helps sustain those exchanges. When someone provides a benefit, expressing gratitude signals that the act was noticed and that the relationship is understood as one in which help may be returned. If the person who helped receives no acknowledgment, they may be less willing to help again. Kurzban describes gratitude as part of the psychological bookkeeping of social relationships: the giver can wonder whether the recipient even noticed the help, and thanks can answer that question.

Williamson offers a practical extension: notice small benefits, not just grand gestures, and celebrate other people’s achievements even when they are modest. He describes arranging a family trip to Lapland for a business partner’s fortieth birthday, but also emphasizes smaller acts, such as remembering someone’s preferred drink. Because people may find it easier to celebrate friends than themselves, celebrating others can help establish a reciprocal norm in which accomplishments are noticed and marked.

His examples distinguish a large, memorable gesture from the everyday signals through which people show attention. A surprise family trip can prompt an obvious response of gratitude. A can of someone’s preferred drink, bought because you remembered what they like, is smaller but still demonstrates attention. Williamson argues that people who notice these small acts should also express appreciation for them; otherwise, the resolution at which they notice benefits may not match the gratitude they communicate.

Kurzban says he is generally skeptical about clinical psychology, but he sees a plausible case for gratitude practices helping people feel happier, more content and calmer. He also recalls the economic idea of “goodwill accounting”: people keep track of benefits and signal that they recognize what someone else has done. His point is that ideas about exchange and trust in economics may be useful for understanding social relationships, not just markets.

Trust estimates whether another person will do what they say. It can enable exchanges that would otherwise be difficult, while leaving someone vulnerable to being taken advantage of. Kurzban describes trust as relevant to both the likelihood of a person keeping a commitment and the magnitude of what is at stake. Trust can make exchange possible, but mistakes in either direction matter: trusting too readily can expose someone to loss, while withholding trust can block a beneficial relationship.

Law and contracts extend trust by making some commitments enforceable, but they cannot cover every private relationship. A confidential conversation with a friend may have no legal protection, while professional confidentiality depends partly on formal rules. Kurzban sees such institutions as tools that allow people to take interpersonal risks they would otherwise avoid. He compares them with religious confession, where privacy was also supported by cultural and religious penalties. Formal protections can enlarge the range of situations in which people are willing to cooperate, while emotional trust helps people navigate the many settings those protections do not cover.

Depression is more serious and uncertain than many of the other feelings discussed. Kurzban emphasizes that it can be devastating and says he has experienced it himself. He recalls being told to “just feel happier” and rejects that as unhelpful. The evolutionary proposal he discusses is not a reason to minimize the condition.

Drawing on work by Ed Hagen, Kurzban describes one possible account: depression may function partly as bargaining, with withdrawal and other behavior signaling a need for support. He mentions postpartum depression as a context in which demands on a parent can increase sharply. A new child needs care, and a parent may need more help. The proposal is that depression-related behavior might make that need more apparent to people around the person.

Williamson presses on the apparent contradiction: if withdrawal is part of a signal of need, why would depression make a person less social? Kurzban suggests that withdrawal may impose a cost on others. A group may need that person to join a game, a work meeting or a shared task; the absence makes the need harder to ignore. He illustrates this with the missing fourth person for Monopoly or the missing partner for doubles pickleball.

Kurzban does not describe this as a conscious strategy or say that withdrawal reliably brings support. He offers it as a possible account of what the behavior might do within relationships. The suggestion that withdrawal imposes a cost on others is not the same as saying that someone chooses depression in order to bargain.

The low energy and painfulness of depression prompt further questions in the exchange. Kurzban wonders whether the severity of the experience might contribute to the signal of need, while also making withdrawal more likely. He suggests that the painfulness may be part of the system that prompts withdrawal and makes the need legible to others. He also raises a different possibility: withdrawing may leave someone more time to review a life that appears to be going badly.

Kurzban recalls John Tooby observing that graduate students can receive a persistent stream of discouraging signals—low status, little money, little recognition and few publications. Tooby’s remark to Kurzban, “you could be replaced,” was meant as a blunt reminder of that environment, though Kurzban describes him as a wonderful advisor. Kurzban asks whether a system might prompt someone to step back and consider whether their current direction is working.

The bargaining proposal concerns possible effects on relationships; the review-of-life proposal concerns withdrawal and attention. Neither tells a person why they are depressed. Kurzban leaves both as exploratory explanations.

Embarrassment, Kurzban suggests, often follows a breach of a social norm: a fly left down, a burp at a wedding, or another visible mistake. He proposes that the blush may serve as an involuntary signal that the person knows a norm was broken and did not intend to break it. A verbal apology can be strategic; a flush is harder to fake. On this account, the signal may reassure observers that the person recognizes the norm and is likely to follow it in the future.

He distinguishes shame from embarrassment by the perceived intention behind a violation. Embarrassment can mean, “I broke a norm and may not have meant to”; shame can arise when someone believes they broke a norm intentionally, or that others think they did. Kurzban suggests that hiding or lowering one’s profile may signal recognition of the violation and a willingness to accept social costs while showing an intention to change.

Shame can also arise after events that were not the person’s fault, including assault. Kurzban speculates that this may reflect a person’s sense of how others now value them, rather than a judgment that they caused what happened. In that explanation, shame responds partly to what someone believes other people believe. It should not be read as evidence that the person is responsible for the event.

The discussion returns to embarrassment through two ordinary accidents. Williamson wonders whether tripping when alone can feel funny because the person can imagine the social cost without actually being seen. Kurzban agrees that bumping into a glass wall alone might prompt someone to think, “I’m an idiot,” while the same accident in front of another person can produce an immediate “I’m fine.” Williamson recounts coming off a moped in Bali and noticing that his first response was to reassure the people with him before checking how badly he was hurt.

Kurzban says he does not have a settled explanation for that reflex. He suggests it may communicate that the person understands the mishap and is competent in general, even if they have just made a mistake. Williamson adds that blaming the bike can move responsibility away from the rider: the equipment failed, so the event need not indicate that the person will repeat the same error. Their examples return to the social dimension of embarrassment: the person may be managing how others interpret a visible failure.

Kurzban extends the measure-and-motivate framework to mental effort. Concentrating on a difficult task uses capacities such as working memory that could be applied to other things. The unpleasant feeling of effort may register the opportunity cost: while someone is multiplying numbers or persisting at a problem, they cannot use the same mental resources for planning, remembering or another task.

Boredom may work in a related way. It registers that the current activity is not rewarding and suggests that something else might be a better use of attention. In both cases, the mind monitors what it is doing and the possible alternatives. Kurzban finds this recursive arrangement striking: one part of the mind must in some sense track the work of another part, while also estimating what else it could be doing.

Feelings often arise whether someone wants them to or not. What remains more open to choice is how to respond. Asking what a feeling is measuring and what action it is urging can help distinguish the signal from its suggested behavior.

Williamson describes one way to reduce the self-judgment that can follow an unwanted emotion. In his meditation practice, rather than treating a wandering thought as something to push away, he tries to welcome the part of himself that produced it. A work thought during meditation might come from a part trying to be successful or responsible. Acknowledging that motive can make it easier to let the thought wait without condemning oneself for having it.

Kurzban sees a connection between this practice and the evolutionary view of the mind as made up of different systems. An emotion can have a function and still be poorly timed or unhelpful in a particular situation. Recognizing that it has appeared is different from giving it control. The decision still depends on the present circumstances, the costs of acting and the alternatives available.

Envy, for example, may appear even when someone is grateful for their life and has no reason to pursue the comparison it presents. Kurzban says he experiences envy despite having a partner, family and circumstances he values. He does not expect to erase the feeling; he can recognize what it is trying to do and decide that he is already pursuing what matters to him.

Williamson’s account of welcoming a thought adds a point that is not simply “ignore the feeling.” He describes treating a distracted or frustrated part of the mind as an effortful but well-intentioned participant, rather than as an enemy to suppress. Kurzban connects that stance to the modular view of the mind: different systems can make competing demands, and a person can acknowledge them without treating any single demand as the whole self.

Kurzban’s framework treats feelings as signals with possible functions, not commands that must be obeyed. For some feelings the proposed function is clearer than for others; depression, yawning, déjà vu and nostalgia remain among the cases he describes as understudied or hard to explain. Asking what an emotion may be measuring can make its prompt legible, but it does not settle what a person should do.