Within the field of linguistics, the most hotly contested aspect of gesture revolves around the subcategory of Lexical or Iconic Co-Speech Gestures. Adam Kendon was the first to hypothesize on their purpose when he argued that Lexical gestures do work to amplify or modulate the lexico-semantic content of the verbal speech with which they co-occur. However, since the late 1990s, most research has revolved around the contrasting hypothesis that Lexical gestures serve a primarily cognitive purpose in aiding the process of speech production. As of 2012, there is research to suggest that Lexical Gesture does indeed serve a primarily communicative purpose and cognitive only secondary, but in the realm of socio-pragmatic communication, rather than lexico-semantic modification.