in schizophrenia, the process of transforming abstract concepts into concrete representations or forms. For example, an individual with paranoid schizophrenia who experiences feelings that the whole world is hostile may later become convinced that the neighbors are trying to harm him or her. If this individual should then begin to have specific perceptual experiences that support this conviction, such as auditory hallucinations of threatening remarks made by the neighbors, perceptualization of the concept has occurred; this is the most advanced level of active concretization. [defined by Italian-born U.S. psychiatrist Silvano Arieti (1914–1982)]