Over the past few years, psychologists have bombarded us with study after study on the importance of first impressions. An attentive observer, we've learned, can predict whether or not a job seeker will be successful just from watching the first 15 seconds of an interview. We can form a lasting judgment of a stranger's trustworthiness or dominance based on her enunciation of the word "hello."

Yet even as awareness of the power of snap judgments has grown, the conventions that govern first-time meetings have continued to fall away. The opportunities for bungling a social or professional introduction are practically unlimited, from the language you use to the physical greeting. Should you go for a handshake? A hug, a nod, a wave? Is there anything worse than misinterpreting a handshake as an invitation to a hug, and finding yourself hovering mid-way, arms outstretched, while your adversary offers you a palm?

At least one part of the introduction remains fixed: You have to say your name. But even this presents a conundrum. Should you give your full name, or just your first, or what about the ballsy last-name first intro ("The name's Bond … James Bond")? Does saying your full name convey confidence and gravitas—or is it unfriendly, overly formal, even presumptuous? It can seem dramatic: "Don't you know who I AM?" it seems to say. "Perhaps my reputation precedes me."

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And are women more inclined to soften their introductions by sticking with their first names? At a panel on networking last year, Cosmopolitan editor-in-chief Joanna Coles admonished a colleague for a first-name-only introduction, which she interpreted as a symptom of self-doubt. "Why is it that when women introduce themselves, they say their names in a long, drawn-out way and only give their first names?" Coles asked. "A lot of men I know will say 'Hello, Bob Jones' in a very assertive tone, whereas women will just say, 'I'm Sarah.'"

Coles was on to something. One linguist I spoke with, Orin Hargraves, hypothesized that the reason men might give their full names more often is that they are more likely to have common first names: Nine of the top ten most common names in 2013 were male. ("Mary" sneaks in at number seven.)

Regardless of the reason, Coles was also right that the mode of introduction has an impact. Blogger Lily Herman began implementing her advice, and although she admits she "felt kind of ridiculous" at first, she reports that her full name actually elicited a better response. Lifestyle writer Joanna Goddard reached the same conclusion a few years ago: After reflecting on an awkward incident at a party, when she introduced herself as "Joanna," while her boyfriend gave his full name, she concluded that using your full name is "more powerful, more adult and makes more of a statement."

Linguists assert that there's a subtext behind the way you introduce yourself. Will this be the relationship of a boss/employee, teacher/student, avenger/victim? The introduction can indicate not just the current state of the relationship, but what you think it could become. A full-name intro acknowledges an acquaintance's need for "independence" and maintains a respectful distance. A first-name-only intro, on the other hand, satisfies a need for what linguists call "involvement"—feelings of closeness or intimacy.

Both strategies can be polite, but neither is risk-free. "If you choose to use a more formal strategy with someone, you risk being perceived as snobby, status-obsessed, or uptight," says linguist Nic Subtirelu, founder of the blog Linguistic Pulse. A friend encountered this very dilemma on her first day at a new job: At an orientation session, she introduced herself with her full name, and then watched, in mild horror, as everyone else around the table used just their first. "If you choose a more informal strategy with someone, you run the risk of finding it harder to have them view you as someone with authority," says Subtirelu, "whether that's them trusting your knowledge or following your directives." Perhaps the friend wasn't so out-of-sync after all?

Additional research suggests that full names do convey authority and even intellect. According to a study published last year, writers are perceived as higher-status and more intelligent if they list a middle initial (or two or even three): Psychologists had students read a writing sample whose author was listed as David Clark, David F. Clark, David F.P. Clark or David F.P.R. Clark. The more middle initials the author used, the more highly his writing was regarded.

For etiquette experts, the issue is unambiguous, especially in professional settings. "When in doubt, always go with the full name," advises Lizzie Post, a great-great-granddaughter of Emily Post and an author of three books on manners. In business, "Your name is essentially your brand," she told me. In a social setting, she suggests considering the age and status of a new acquaintance. "If I'm meeting someone more than five to ten years older than me, I tend to use my full name. If it's a peer group, I'll often use my first name."

According to Steven Petrow, who writes the Washington Post etiquette column "Civilities," "The best default is to introduce yourself by your full name—first and last—in both business and social situations. Why's that, especially in this age of lax rules and casual comfort? Because the purpose of introducing yourself is to be found again. You can't be found without a last name." In the age of social media, that might not be entirely true. If you're meeting someone at a party or event, a first name is usually enough to find each other—whether by scanning the host's invite list, going through the host's Facebook friend list, or finding some other identifying detail, like workplace or alma mater. After failing to exchange numbers, Washington Post weddings writer Ellen McCarthy connected with the man she later married through a post-party friend request.

At work, different forms of digital communication have also changed the way we represent our names. It might be less necessary to announce our full name when we remind our colleagues of it every time we shoot off an email, when we interact as avatars and initials on the chatting software Slack. They are bombarded by identifiers all day long.

The most important thing is probably to figure out what the norm is and conform to it. If you're in the Netherlands or Japan, you might be violating protocol if you don't give your full name to your elders. Even in the U.S., there are regional variations. According to Petrow, who lives in North Carolina, southerners—who tend to put greater stock in their heritage—may be more inclined to state their full name, even including a middle name to signify their maternal lineage. Meanwhile, "In the West, which pretends to be classless—at least in the old East Coast ways—people tend to introduce themselves by only their first name," he says. "If I met Mark Zuckerberg, I'm sure he'd say, 'I'm Mark.'"

But don't fret too much: According to one study, we form a lasting impression within just one tenth of a second of meeting someone. So by the time you open your mouth, it might be too late.

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