The concept of priming refers to a specific psychological phenomenon that occurs without consciousness of it, in which the exposure to a certain stimulus decisively influences cognitive processing affecting the responses given to subsequent stimuli. In 1971, Meyer and Schvaneveldt designed some experiments that consisted in presenting pairs of lexical sequences (word-word, pseudoword-pseudoword, and word-pseudoword) simultaneously to subjects, in such a way that the first sequence was displayed above the second as a ‘mask’. After that, subjects had to indicate if the lexical sequence was a word or not; subjects’ reaction times were measured. Meyer and Schvaneveldt discovered that subjects’ reaction times were shorter when the pair of lexical sequences was semantically related (for example: ‘bread’ and ‘butter’). Currently, numerous studies explore other types of relationships (for instance, perceptual relationships, phonological ones, etc.).