Those who watched the New Hampshire Republican debate surely made a mental note of aspects of the candidates’ appearances as they staked out their turf: Ted Cruz’s jutting chin, Ben Carson’s avuncular temples, Donald Trump’s blond, blond hair, Marco Rubio’s full cheeks and boyish manner.

It’s all window-dressing, you might say; only the candidates’ positions matter. But in politics, looks count more than we care to admit.

Indeed, we often clinch our political decisions a split-second after we see a candidate and don’t change them much over time. In a 2006 study published in Psychological Science and led by Alexander Todorov of Princeton University, subjects who selected favorites after a brief glance at snapshots of unfamiliar candidates were able to predict who would win nearly 70 percent of the 2004 Senate and House races. When the researchers gave people more time to decide, they simply confirmed their first impressions.

In another study, published in 2008 in the Proceedings of the National Academy of Sciences, Prof. Todorov and colleague Nikolaas Oosterof digitally manipulated people’s facial features in photos, revealing just what makes us fall so hard for a candidate. They showed that a rounded, baby-faced appearance with prominent cheekbones, arched inner eyebrows and a sunny demeanor makes a person seem trustworthy.

Such snap judgments also can skew life-or-death decisions, according to a new study in Social Psychological & Personality Science.Assessments of the trustworthiness of convicted murderers based on their facial features aligned well with how they were sentenced. The sense that a prisoner was trustworthy was a good predictor of whether he got life in prison or the death sentence.

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