Two semantic systems in the brain for rapid and slow differentiation of abstract and concrete words.

Most studies of semantic processing address changes in the late (300-800 msec) components of evoked potentials. However, recent years have seen the appearance of data showing that humans can perceive the sense of stimuli presented to them in significantly shorter periods of time. We report here studies of the mechanism of semantic analysis of written abstract and concrete words in four series of experiments: 1) reading of words on a monitor screen; 2) simple classification of all presented words into the categories "abstract" and "concrete;" 3) complex, i.