From entry sub-symbolic systems in glossary Artificial Intelligence: humans at the heart of algorithms
Sub-symbolic systems are those which use low-level representations such as the weights in a neural network or the artificial insects in swarm computing. One could argue that there is still digital symbol manipulation when they execute, but not at a recognisable level. In contrast symbolic systems use symbols such as names, places, and concepts whch are manipulated by explicit rules.
Used in Chap. 1: page 3