CALL me a terrible mother. I have an only child. For now at least, I’m planning to keep it that way, for my happiness and for hers. But the notion that an only child might be a happy one contradicts strong cultural beliefs. According to these, children like mine will end up rotten with selfishness and beset by loneliness.

And negative assumptions about parents who deprive their child of siblings strengthen the general opprobrium against only children. If a child doesn’t have siblings, it’s generally assumed that there’s a hush-hush reason for it: we don’t like being parents (because we are selfish), we care more about our status — work, money, materialism — than our child (because we are selfish), or we waited too long (because we are selfish). When have you heard someone say an only child is better off?

A general picture emerges that only children are loners, misfits and always, always selfish. I don’t buy it. As an only child, with one of my own, and as someone who has just spent three years writing about the subject, I’m convinced that if, by dint of will or biology, you have an only child, you can stop worrying about it.

Don’t take my word for it. Consider the data: in hundreds of studies during the past decades exploring 16 character traits — including leadership, maturity, extroversion, social participation, popularity, generosity, cooperativeness, flexibility, emotional stability, contentment — only children scored just as well as children with siblings. And endless research shows that only children are, in fact, no more self-involved than anyone else. It turns out brutal sibling rivalry isn’t necessary to beat the ego out of us; peers and classmates do the job.

Nor are only children lonelier. Toni Falbo at the University of Texas and her colleague Denise Polit are among the many researchers who have explored the question of whether only children are lonelier than those who have siblings. Their findings suggest that solitude is not synonymous with loneliness and often strengthens character. As one psychotherapist explained to me, only children tend to have stronger primary relationships with themselves. And nothing provides better armor against loneliness.

An Ohio State survey of more than 13,000 children found that only children had as many friends as anyone else; many of the only children I interviewed had cherished and nurtured friendships that they often regarded with a familial sense of permanence and loyalty.

The differences between only children and those raised with siblings tend to be positive ones. Ms. Falbo and Ms. Polit examined hundreds of studies in the 1980s and found that only children had demonstrably higher intelligence and achievement; only children have also been found to have more self-esteem. These findings, which have been confirmed repeatedly in recent years, hold true regardless of whether parents of only children stayed together and regardless of economic class.

Researchers like the sociologist Judith Blake believe these qualities result from the fact that parents who have just one child are able to devote more resources — time, money and attention — to them than parents who have to divide resources among more children.

The idea that only children are precocious persists and may, as Ms. Blake suggests, be connected with the fact that only children are often raised in richer verbal environments and share meals and other activities with adults. (I love it that an artist friend still brags that my daughter was 2 when she insisted that a crayon was “magenta, not pink.”)

My research suggests that only children experience more intensely emotional family lives. The parental gaze is more focused; the love more concentrated. This intensity can be enriching, and also suffocating. Many adult only children told me that they wanted their first child to have a sibling precisely because this kind of intensity was too much for them.

At the end of their parents’ lives, only children are sometimes said to be burdened in ways that children with siblings aren’t. Data from the National Alliance for Caregiving show that, in fact, the closest living sibling most often shoulders responsibility for elder caretaking. Still there is something existentially troubling about the idea of facing one’s parents’ mortality alone; in my interviews with hundreds of only children, I found that this was the issue people felt most viscerally about when deciding whether they wanted to have one or more children.

Given that about one in five American families now have just one child, this seems like a good time to question the misconceptions about only children and the dangers of raising a child without siblings. For one thing, one-child families make obvious sense in a time of diminishing resources. This may explain recent studies showing that parents who have one child tend to be happier. (In a recent study at the University of Pennsylvania, for example, Hans-Peter Kohler surveyed 35,000 sets of twins and found that of those women who had children, the happiest ones were those who had just one child.) Call me selfish but, as the mother of one child, I enjoy more time, energy and resources than I would if I had more children. And it is hard to imagine that this isn’t better for my family as well as for me.

Most people say they have their first child for themselves and the second to benefit their first. But if children aren’t inherently worse off without siblings, who is best served by this kind of thinking? Instead of making family choices to fulfill breeding assignments we imagine we’ve been given, we might ensure that our most profound choice is a purely independent, personal one. To do so might even feel like something people rarely associate with parenting: it might feel like freedom.