Sometimes Koko’s use of sign language is augmented with other forms of communication with Penny. A simple non-ASL gesture or facial expression may clarify a point. After interacting with each other for so long, deeper levels of communication evolve – as in our own interpersonal relationships. We don’t always say what we mean, or mean what we say. Either do gorillas; emotions play a role, and this must be part of any long-term interspecies communication study or endeavor.