We are sometimes wrong about what makes us happy. I am writing this on the Amtrak train between New Haven and New York in the quiet car, where conversation is discouraged. I chose this car because it lets me focus on my work and because I prefer the solitude. Others share my preference: when Nicholas Epley and Juliana Schroeder asked residents of Chicago about their daily commute, most said that they would prefer a solitary ride.
They were wrong. The researchers went on to do an experiment in which they told some commuters to "enjoy their solitude" and not talk to other people and told other commuters to make a point of starting up a conversation with a stranger. When later asked, both introverts and extroverts who were instructed to interact with strangers had a much more pleasant time.
Dozens of other studies illustrate our mistaken theories about what makes us happy. People tend to overvalue the hedonic effects of big houses and fancy cars and undervalue the pleasures of new experiences and new people. Most of all, we miss out on how good we are at getting used to both positive experiences (like a new car) and negative experiences (like just missing a train)—a capacity that psychologist Daniel Gilbert calls "the psychological immune system."
All this research seems to lead to a recipe for living the good life. When trying to figure out what makes you happier, don't trust your gut; check out the data. Gilbert approvingly quotes the 17th century writer François de La Rochefoucauld: "Before we set our hearts too much upon anything, let us first examine how happy those are who already possess it."
This is good advice—but it only goes so far. I've become convinced that there will never be a complete scientific solution as to how to maximize our happiness. This isn't because of the usual worries that happiness is elusive, or hard to define, or falls somehow beyond the domain of science. (I don't believe any of that.) Rather, the problem lies in our inability to figure out the right balance between the happiness of different selves.
To see what I mean by this, consider a more familiar problem. We make trade-offs concerning the welfare and happiness of different people. I care about myself, and so, other things being equal, I'd like to be happy. But I also care about my wife and children and, to a lesser extent, about my neighbors, and, at least a bit, about strangers. And so I will give up some of my happiness for the sake of others. I will give my kidney to a family member, with all the risk and inconvenience that this involves. I won't do this for neighbors or strangers, but I will help them out in smaller ways, even if it means taking away a bit of my own happiness.
This brings us to what is perhaps the hardest moral problem of all: Just how much of our own happiness (however one defines it) are we obliged to give up for the sake of others? Some libertarians and hedonists say that the answer is none, while some consequentialists would answer "almost all of it," as they believe that we are obliged to maximize the sum total of happiness across all conscious beings, regardless of how unhappy we may be personally as a result. Most of us fall somewhere in the middle, agreeing that we have some obligation to others, but struggling to determine the extent of this obligation. Yes to giving money to the beggar on the street; no to giving him our kidney.
So far, this is a moral problem, not a problem in how best to maximize one's happiness; a cold-blooded hedonist would only help others to the extent that she believed it would increase her own happiness. But now consider that the same trade-offs apply for a single individual, within a single lifespan. Think of your happiness now and ask yourself how much you will give up, not for your brother or neighbor, but for yourself one week from now, one year from now, or decades from now.
Presumably, the answer isn't nothing—anyone who saves money for retirement is sacrificing the happiness of Present Self for that of Future Retired Self. So is anyone who puts off an enjoyable experience for the future, or does something unpleasant now to make life more pleasant later. But it also isn't everything. Anyone who procrastinates is choosing to make Present Self happier at a cost to the happiness of Future Self. Indeed, any choice to experience a one-shot pleasure now rather than later (seeing a certain movie for the first time, say) is prioritizing Present Self over Future Self.
It might seem perverse to think about oneself in the future as akin to a different person, but quite a bit of data from experimental psychology suggests that we often do just this. Not for ourselves five seconds from now or five minutes from now, but for ourselves in the distant future. For instance, we tend to overestimate the influence of an individual's inherent personality in explaining his behavior, and underestimate the influence of the situation. We don't tend to do this for our own behavior—unless we are thinking of ourselves in the distant past or the distant future. Then we think of ourselves in the same way as we think of anybody else.
One vivid illustration of the notion that we are multiple selves over time concerns the phenomenon known as "self-binding"—acting now to thwart our desires in the future. Ulysses had his sailors tie him to the mast of his ship, so that Future Ulysses could hear the song of the sirens without succumbing to the urge to jump into the sea after them. Smokers and drinkers and overeaters tell their friends not to enable them in the future, no matter how much they beg, and you can sign a contract with casinos in Illinois stating they will confiscate your winnings if you ever gamble there. When you think of what's going on here, it's exquisitely complicated: We act now to block the desires of our future self (the pleasures of a cigarette, say) for the benefit of yet another further future self (who would suffer the pain and risk of addiction).
The situation that I'm describing is not quite what Walt Whitman was talking about, but a single life really is large, containing multitudes. This complexity means that the project of maximizing a single person's happiness shares certain properties with the project of maximizing the happiness of a group of individuals. Thus even if you have a perfect and precise definition of happiness, there is no single right answer to how to live a happy life.
Paul Bloom is Brooks and Suzanne Ragen Professor of Psychology & Cognitive Science at Yale University and author of How Pleasure Works: The New Science of Why We Like What We Like.