It is often possible to make known what one wants and what he is thinking about by means of gestures, without the use of words, and it may be that men talked by signs before they used spoken language. ... This sign, which is used rather widely among boys, would not understood without explanation. (新潟大)
――ビジュアル英文解釈 PART II 伊藤和夫著 駿台文庫