Information provides the basis for anticipating and dealing actively with events. Communicating animals both provide and respond to specially packaged information yielding particularly useful clues to their mental operations. This chapter examines features of communication and cognition that raise problems for designing and interpreting research. First, animals' signals can provide information about a signaller's behavior, identity, and external stimuli to which it is responding. Attempts to understand both mental and social processes are impeded if this diversity of information is not considered or if behavioral information is underestimated or confounded with information about “affect” or “arousal”. Second, in moment-by-moment responding animals must continuously select among signals and other stimuli and rank them as focal or contextual. Animals probably generate predictive scenarios based on both current and stored information and compare and select among competing scenarios as events develop. The presence of expected information may lead quickly to “typical case” judgments, but its absence could engender “worst case” predictions. Experimental control of contextual sources of information can create circumstances in which stored information (often not controllable) gains heightened influence. Because context-dependent responding is complex and flexible, investigators must be especially careful in considering the kinds and sources of information that are involved.