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AAAI2021/tex/introduction.tex

 \section{Introduction}
 \label{sec:introduction}
 
-
-
 The emergence of human language has always been an important and controversial
 issue. This problem attracts attentions from a broad range of communities,
-including philology, biology and computer science. In computer science,
-researchers induce and analyze the emergent language in multi-agent systems by
-setting up communication scenarios, such as referential games and
-communication-action policies.
+including philology~\cite{}, biology~\cite{}, and computer
+science~\cite{}. Especially in computer science, efforts in recent years try to explore
+the emergence of symbolic language in virtual environments, where agents are trained 
+to communicate with neural network based method, i.e, deep reinforcement
+learning~\cite{}. For example, \note{XXXX}
+%Such works can be roughly classified into two categories,
+%referential game~\cite{} and multi-agent reinforcement learning (MARL)~\cite{}, based on
+%the environment setting.  
+
+
+To evaluate the emerged symbolic language, compositionality is widely used and
+taken as an important metric. 
+
+
 
-Compositionality is a widely used metric to evaluate the emergent language. It
+It
 is a concept in the philosophy of language [1], which describes and quantifies
 how complex expressions can be assembled out of simpler parts [2]. For example,
 Figure1(a) shows a perfect compositional language (with maximum