Fifty years ago, the pioneering industrial designer Henry Dreyfuss—most often remembered for his revolutionary modernization of alarm clocks and thermostats—published Symbol Sourcebook, a comprehensive guide encompassing everything from road signs and agricultural symbols to religious and sports images. Since then, signs have become an even more crucial aspect of communication. They signal political and social affiliations and, as we see with emojis, replace emotion itself. Cooper Hewitt’s new exhibition, “Give Me a Sign: The Language of Symbols” explores the history of conceptual imagery and its role in the evolution of global communication. —Lucy Horowitz