Conference interpreting is the oral translation of speeches simultaneously. It has existed since ancient Egypt when it was used to translate between languages. Modern conference interpreting emerged with the need for translation at international meetings after World War I and other events like the Nuremberg trials. Most conference interpreters work between two or three languages which include their native language and other languages they have mastered. Early research on conference interpreting in the 1950s and 1960s studied how factors like source language and speech speed affected interpreter performance.