There are people whose intelligence can be gauged at once by their voice and laughter.
 Anton Chekhov, The Steppe (1888). copy citation

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Author Anton Chekhov
Source The Steppe
Topic intelligence laughter
Date 1888
Language English
Reference
Note Translated by Constance Garnett
Weblink https://en.wikisource.org/wiki/The_Steppe

Context

“Another waggoner, a short stubby little man with a bushy black beard, wearing a waistcoat and a shirt outside his trousers, ran up to him. The latter broke into a deep guffaw of laughter and coughing and said: "I say, lads, Dymov has killed a snake!" There are people whose intelligence can be gauged at once by their voice and laughter. The man with the black beard belonged to that class of fortunate individuals; impenetrable stupidity could be felt in his voice and laugh. The flaxen-headed Dymov had finished, and lifting from the ground with his whip something like a cord, flung it with a laugh into the cart.” source