There is activation-based triggering and firing of production rules. The moment of selection of syllable program nodes is also determined by a ratio of activations, such that how fast selection occurs depends on how active other nodes are. Planning latencies Given the equations for spreading activation and production rule firing, the mathematically expected mean planning latencies can be computed. A mere associative link between two nodes tells nothing about the relation between the entities represented. The importance of representing the relation between entities was recognized by Otto Selz in the beginning of the 20th century, and labeled link have become a central part of semantic networks in Artificial Intelligence since the seminal work of Ross Quillian in the late 1960s.
Verification is the use of goal-factored production rules as a means of selection.
Our knowledge of how the brain works is still so rudimentary that is seems premature to ban reference to production rules and other symbolic entities such as labeled links. Moreover, the line between production rules and many connectionist constructs is rather thin. For example, production rules without variables can easily be implemented using a connectionist network. Furthermore, proposals have been made for how a connectionist system may achieve variable binding, in effect implementing production rules with variables. Production rules mean nothing more than the operations that they specify.