Université Paris VI, CHU Pitié-Salpêtrière, Paris
The role of speech in the regulation of behavior was described in child psychology by LS Vygotsky and AR Luria in the Soviet Union during the twenties, and extended to neuropsychology by Luria after the World War II. According to Vygotsky, man built up « psychological tools » on the model of material tools to extend his natural capacities. Psychological tools, such as language, are symbolic systems from social origin, which control activity and behavior, and convert natural cognitive processes into higher cortical functions. Therefore child's development is embedded into particular social relationships. First communicational speech then inner speech plays a major role in the regulation of behavior in man: at first it goes with action, then precedes it, and finally replaces it. A willful action is thus an action largely controlled by inner speech, especially in novel and complex tasks, but the properties of inner speech differ from those of communicational speech. Assessment of the role of speech on the regulation of action and behavior should be part of the neuropsychological examination of frontal lobe functions. It also could be useful to assess the ability of patients to participate in cognitive rehabilitation, particularly in Alzheimer's disease.