McClelland and Rumelhart (1981) and Rumelhart and McClelland (1982) developed a model of word perception called the Interactive Activation (IA) Model. The central feature of this model assumes that the processing of information during reading consists of series of levels corresponding to visual features, letters and words. This model is used to explain the word superiority effect (WSE) which refers to a phenomenon where people recognize letters more easily if presented within words as compared to isolated letters, and to letters presented within non-word (orthographically illegal, unpronounceable letter array) strings. The effect was first described by Cattell (1886), and important contributions came from Reicher (1969) and Wheeler (1970).

Source: Chase, C. H. and Tallal, P. (1990). ‘A developmental, interactive activation model of the word superiority effect’, Journal of Experimental Child Psychology 49, 448-487