There are different theories regarding what the N4 in a priming paradigm reflects. The often quoted mechanisms are those of Neely and Keefe (1989), who purport that these mechanisms are automatic spreading activation, expectancy and semantic matching. The latter two are generally referred to as controlled processes. According to the automatic spreading activation theory, presentation of a word is thought to activate the corresponding conceptual representation in the semantic network, and the activation automatically spreads to related nodes, thereby increasing their activation level and reducing the processing time of the related words (Collins and Loftus, 1975). Expectancy is the second mechanism used to explain the priming effect. It is assumed that based on the prime, subjects generate expectancy for a set of semantically related targets. Targets that are expected are recognized more quickly compared to targets that are not expected. This mechanism is said to be influenced by the instructions and the proportions of prime-target pairs (den Heyer et al., 1983; Neely and Keefe, 1989; Silva-Pereyra et al., 1999). In general, semantic matching is also referred to as a post-lexical
