Reading, like writing, is a complex cognitive activity that is essential for individuals' adaptation and integration into modern society. For several decades, various disciplines have been interested in studying the mental processes underlying these activities. Understanding these processes has led to insights into efficient reading and writing, as well as into the acquisition of these skills and the particular difficulties that may arise during their learning. This line of research aims to: 1. Contribute to the study of the processes involved in written language in Spanish-speaking populations to understand the specificities of Spanish speakers. 2. Characterize delayed and dyslexic readers in Spanish, identifying subtypes, determining their incidence, cognitive profiles, and comorbidity with other disorders. 3. Analyze and evaluate variables that impact the learning of reading and writing. 4. Study access to written language in different writing systems, as well as in individuals with auditory and visual impairments. 5. Develop written language assessment tests with psychometric criteria for both educational and clinical use. 6. Analyze methods of teaching written language and teaching practices in our context. 7. Develop and implement intervention programs for individuals with difficulties in written language and for those in socially vulnerable contexts or at risk of reading difficulties.