The ability of symbolic representation is the ability to acquire signs and systems of sounds. Acquisition of language as a system of sounds rests on the ability of differentiation, which enables the phenomenon of language sign as a discrete, distinctive unit of the language system, as well as the possibility of combining them in accordance with formal-syntactical principles. The ability of differentiation depends on the process of decentration, which represents a complex achievement of cognitive and emotional development. The basic thesis presented in this paper is that the process of decentration is connected with the effectiveness of the function of mentalization, determined by the French psychoanalysts as pre/conscious ego-activity which transforms and elaborates basic somatic and instinctive-affective experiences into psychic contents. The function of mentalization develops within the pre-verbal communication with the primary object, through internalization of its capability to recognize and articulate first primitive emotions and different somatic and sensory excitations, which the early mental apparatus finds overwhelming and meaningless. Chronic incapacity of the primary object to shape the experience disturbs the establishment of the mentalization function and leads to initiating the mechanism of projective identification through which the psychic apparatus tends to free itself from raw, unformed, traumatic sensations. One of the consequences of excessive use of this mechanism is the impossibility of differentiation between the subject and the object, which reflects on the cognitive and emotional development of the individual. In schizophrenic patients, in which, due to ineffectiveness of the function of mentalization and excessive use of the mechanism of projective identification, extreme blending between the self and the objects ensues, language forms may be damaged: differentiation between the sign and the signed melts, words lose their conventional meaning and are used in idiosyncratic way, and due to major or minor collapse of syntactic principles, their utterances may become poorly organized and non-communicable. Deficient ability of symbolic representation in schizophrenic patients stems from the pathological condition of their mental apparatus, which, according to modern studies in the domain of genetics, comes as a result of combined effects of genetic disposition and experiences with primary objects. The results of these studies indicate that the ability of symbolization is an intricate problem that needs to be considered in the light of complex interaction between constitutional and environmental factors.