As the nonplayable characters (NPCs) of squad-based shooter computer games share a common goal, they should work together in teams and display cooperative behaviors that are tactically sound. Our research examines genetic programming (GP) as a technique to automatically develop effective squad behaviors for shooter games. GP has been used to evolve teams capable of defeating a single powerful enemy agent in a number of environments without the use of any explicit team communication. This paper is an extension of our paper presented at the 2008 Conference on Artificial Intelligence and Interactive Digital Entertainment (AIIDE'08). Its aim is to explore the effects of shared perception on the evolution of effective squad behaviors. Thus, NPCs are given the ability to explicitly communicate their perceived information during evolution. The results show that the explicit communication of perceived information between team members enables an improvement in average team effectiveness.