"Connectionism" is an approach within cognitive science that employs neural networks, rather than computer programs, as the basis for modeling mentality. A connectionist system, or neural network, is a structure of simple neuronlike processors called nodes or units. Each node has directed connections to other nodes, so that the nodes send and receive excitatory and inhibitory signals to and from one another. The total input to a node determines its state of activation. When a node is on, it sends out signals to the nodes to which it has output connections, with the intensity of a signal depending upon both (1) the activation level of the sending node and (2) the strength or "weight" of the connection between it and the receiving node. Typically at each moment during processing, many nodes are simultaneously sending signals to others.

When neural networks are employed for information processing, certain nodes are designated "input...