The quality of being too willing to believe things without checking if they're true; easiness to fool.
From 'gullible' (easily deceived), formed with the suffix '-ity' (which makes nouns expressing qualities or states). 'Gullible' itself comes from 'gull' (to deceive).
Gullibility isn't stupidity—smart people fall for sophisticated scams because they're trusting! Psychologists say it correlates with being honest yourself, since you assume others are too.
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