“This is the story of the next half-century,” Foer told me, “as we become effectively cyborgs.”

Basically, we are outsourcing our brains to the cloud. The upside is that this frees a lot of gray matter for important pursuits like FarmVille and “Real Housewives.” But my inner worrywart wonders whether the new technologies overtaking us may be eroding characteristics that are essentially human: our ability to reflect, our pursuit of meaning, genuine empathy, a sense of community connected by something deeper than snark or political affinity.

The most obvious drawback of social media is that they are aggressive distractions. Unlike the virtual fireplace or that nesting pair of red-tailed hawks we have been live-streaming on nytimes.com, Twitter is not just an ambient presence. It demands attention and response. It is the enemy of contemplation. Every time my TweetDeck shoots a new tweet to my desktop, I experience a little dopamine spritz that takes me away from . . . from . . . wait, what was I saying?

My mistrust of social media is intensified by the ephemeral nature of these communications. They are the epitome of in-one-ear-and-out-the-other, which was my mother’s trope for a failure to connect.

I’m not even sure these new instruments are genuinely “social.” There is something decidedly faux about the camaraderie of Facebook, something illusory about the connectedness of Twitter. Eavesdrop on a conversation as it surges through the digital crowd, and more often than not it is reductive and redundant. Following an argument among the Twits is like listening to preschoolers quarreling: You did! Did not! Did too! Did not!

As a kind of masochistic experiment, the other day I tweeted “#TwitterMakesYouStupid. Discuss.” It produced a few flashes of wit (“Give a little credit to our public schools!”); a couple of earnestly obvious points (“Depends who you follow”); some understandable speculation that my account had been hacked by a troll; a message from my wife (“I don’t know if Twitter makes you stupid, but it’s making you late for dinner. Come home!”); and an awful lot of nyah-nyah-nyah (“Um, wrong.” “Nuh-uh!!”). Almost everyone who had anything profound to say in response to my little provocation chose to say it outside Twitter. In an actual discussion, the marshaling of information is cumulative, complication is acknowledged, sometimes persuasion occurs. In a Twitter discussion, opinions and our tolerance for others’ opinions are stunted. Whether or not Twitter makes you stupid, it certainly makes some smart people sound stupid.

I realize I am inviting blowback from passionate Tweeters, from aging academics who stoke their charisma by overpraising every novelty and from colleagues at The Times who are refining a social-media strategy to expand the reach of our journalism. So let me be clear that Twitter is a brilliant device — a megaphone for promotion, a seine for information, a helpful organizing tool for everything from dog-lover meet-ups to revolutions. It restores serendipity to the flow of information. Though I am not much of a Tweeter and pay little attention to my Facebook account, I love to see something I’ve written neatly bitly’d and shared around the Twittersphere, even when I know — now, for instance — that the verdict of the crowd will be hostile.