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Gopnik is using affect in the sense Merriam-Webster describes as “a set of observable manifestations of an experienced emotion: the facial expressions, gestures, postures, vocal intonations, etc., that typically accompany an emotion” (“Affect”). Yet the sentence employs both affect and effect correctly as nouns.
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It was a family tease, and, like all family teases, was well-meaning in its affect and sharp-edged in its effect. For example, Google will underline “affect” in blue-its marker for “words that are deemed to be grammatical flubs” (Lanaria)-if you paste this sentence by Adam Gopnik into a Gmail message: You may have been taught that affect is a verb and effect is a noun-and so may the folks who created your grammar checker.
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