Emergence of tool use in an articulated limb controlled by evolved neural circuits

Tool use requires high levels of cognitive function and is only observed in higher mammals and some avian species such as corvids. In this paper, we will investigate how the capability to use tools can spontaneously emerge in a simulated evolution of a two degree-of-freedom articulated limb. The controller for the limb was evolved as neural circuits that can gradually take on arbitrary topologies (NeuroEvolution of Augmenting Topologies, or NEAT). First, we show how very broad fitness criteria such as distance to the target, number of steps to reach the target, and tool pick-up frequency are enough to give rise to tool using behavior. Second, we analyze the evolved neural circuits to find properties that enable tool use. We expect our results to help us understand the origin of tool use and the kind of neural circuits that enabled such a powerful trait.