5. Write simply
Showing off your vocabulary has long been a go-to tactic for looking smart.
But verbosity can backfire.
A 2012 Princeton study — with the fitting title "Consequences of erudite vernacular utilized irrespective of necessity: problems with using long words needlessly" — found that clumsily using big words often causes people to think you're less intelligent.
In one of a series of experiments, researchers selected a sociology dissertation abstract with lots of long words and created a "simplified" version by replacing every word of nine or more letters with its second shortest entry in the Microsoft Word 2000 thesaurus. Then they asked 35 Stanford undergrads to read the dissertation and rate both the author's intelligence and how difficult the writing was to understand.
Results showed that the simplified version was perceived as less complex — and its author was judged as more intelligent.
6. Use graphs
A 2014 study by Cornell researchers Aner Tal and Brian Wansink suggests that people are more likely to believe a claim if it "looks and smells" scientific, such as if it's accompanied by a graph.
In one experiment featured in the study, two groups of about 30 participants each read information about a new medication designed to fight the common cold. One group saw a bar graph to illustrate some experimental findings, while the other group didn't.
Results showed that 68% of the group who didn't see the graph thought that the medication would reduce illness, while a whopping 97% of people who saw the graph thought that the medication would do the same.
"The prestige of science appears to grant persuasive power even to such trivial science-related elements as graphs," Tal and Wansink write.
7. Speak expressively
Monotone sounds dull.
"If two speakers utter exactly the same words, but one speaks a little faster and louder and with fewer pauses and greater variation in volume, that speaker will be judged to be more energetic, knowledgeable, and intelligent," writes Leonard Mlodinow, author of "Subliminal: How Your Unconscious Mind Rules Your Behavior."
He continues: "Expressive speech, with modulation in pitch and volume, and a minimum of noticeable pauses, boosts credibility and enhances the impression of intelligence."
Paulo Philippidis / Flickr
8. Look people in the eye
A 2007 study led by Loyola Marymount University professor Nora A. Murphy found that looking your conversation partner in the eye can be huge for your perceived smartness.
In one experiment, 182 undergrads were divided into pairs. One partner in each pair was instructed to try to look smart and competent; the other wasn't given any instructions.
Then the researchers filmed the pairs discussing a preassigned topic for five minutes. Each partner rated the other on perceived intelligence.
When a panel of judges reviewed the recordings, they found that the students told to look smart employed a number of behaviors — but among the only behaviors that worked was looking your partner in the eye while speaking.
"Looking while speaking was a key behavior," Murphy wrote. "It significantly correlated with IQ, was successfully manipulated by impression-managing targets, and contributed to higher perceived intelligence ratings."
9. Act confident
That same 2007 study led by Murphy found that wearing a self-assured expression, as opposed to a serious one, was also a predictor of perceived high intelligence.
Other research suggests that even overconfidence can make you seem more knowledgeable. In one study, participants estimated their own knowledge of geography and then worked in pairs on a geography task. Then they rated each other on how competent they seemed.
Sure enough, students who had overestimated their own abilities were rated more competent by their partners.