The muscles we use to make the long “i” sound are the same ones that form a smile. The muscles we use to make the long “o” sound, meanwhile, are those involved in frowning. Based on this, two German linguists recently carried out a study that shows that vocalizing a long “i” puts people in a better mood than speaking a long “o” sound. And people are more likely to say “i” words when they’re happy and “o” words when they’re feeling negative. These associations might help explain why in many languages there are more positive “i” words—like “like”—and negative “o” words—like “alone” and “D’oh!”
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