PDP modeled after parallel processing of supercomputing. Computer data processing and human mental processing become an analogy to each other. Psychologists study computing to understand human mind and scientists study the human cognition for artificial intelligence. The complexity of intelligence is developed in response to the complexity of the environment. Those symbols could be highly abstract categories and constitute a schema.
Complex cognition arises from an interaction of procedural and declarative knowledge.
Also, there is a short term memory functioning as working memory, which can spread activation throughout the semantic network by production rules . Working memory contains goals that serve as the base of activation. In his view, declarative knowledge must be semantically meaningful, and the procedural knowledge is logical and therefore productive. More importantly, information processing is goal-directed . Hence, ACT is called a production system .