Who thinks, what role, function, does thinking fulfill in the personality?  
Vygotsky (1929/1988: 69) 

Vygotsky in his later years had three research interests - the development of human higher mental functions, the development of personality, and the development of emotion (Kamiya, 2010: 6–8). Vygotsky’s untimely death prevented him from integrating these three streams. The development of higher mental functions means that every higher mental function is mediated by signs (especially language as a psychological tool) and it is socially formed and develops from an interpersonal plane into an intrapersonal one. This transition from outside inward transforms the process itself, changes its structure and functions. Thus, «all higher mental functions are the essence of internalized relations of a social order, a basis for the social structure of the individual. Their composition, genetic structure, method of action-in a word, their entire nature-is social; even in being transformed into mental processes, they remain quasisocial. Man as an individual maintains the functions of socializing. » (Vygotsky, 1931/1997: 106) Regarding the development of personality, Vygotsky elaborated a far–reaching plan to delineate not only a universal law of personality development but also an ontological drama of a concrete individual. The former was crystalized as follows: «The personality becomes a personality for itself by virtue of the fact that it is in itself, through what it previously showed is itself for others. … To paraphrase Marx: the psychological nature of man is the totality of social relations shifted to the inner sphere and having become functions of the personality and forms of its structure.» (Vygotsky, 1929/1988: 56–59) The latter is based on Politzer’s drama, which means a human sense to a concrete individual in his or her concrete life. Vygotsky clearly stated that «my history of cultural development is an abstract treatment of concrete psychology.» (Vygotsky, 1929/1988: 68) The third stream concerns the integrated development of lower and higher emotions with special reference to Spinoza’s monism.

It is reasonable to ask: How would Vygotsky have integrated above mentioned three research interests if he had kept alive any longer? A possible answer can be served. The author proposed Vygotsky’s vertex psychology. (Nishimoto, 2013) Vertex psychology puts the primary significance on the supremeness of personality. According to Vygotsky’s sonorous statement that «we also oppose depth psychology, our psychology is a peak psychology (does not determine the depth of the personality but its peaks)» (Vygotsky, 1933/1997: 137), it is personality itself that determines human behavior and regulates higher mental functions. It is not deep unconsciousness nor non–individual consciousness nor collective unconsciousness. Then, the author depicted the trajectory of ‘personality growth’ (Kudriavtsev & Urazalieva 2011) as the line of the formation of scientific concepts—self–consciousness—personality growth. (Nishimoto, 2013) Personality growth can be embodied along an epistemological vector and an ontological one. The former refers to cultural development, in which new formations emerge according to Vygotsky’s critical and stable periods. The latter concerns the interiorization of social relationships.

In turn, personality determines or regulates higher mental functions, such as thinking, attention, memory, imagination, volition, and emotion. It also influences our speech-how to utilize a language, how to choose words, and more importantly, how we are voicing to others. (Nishimoto, 2012) Namely, personality determines thinking and speech. The author sheds light on Davydov’s theoretical thinking and Bakhtin’s penetrating speech in the presentation.

References

1. Kamiya, E. (2010). Unfinished Theory on Vygotsky: The Rising Spinoza Onto Psychology. Ootsu: Sangaku Publishing Company.
2. Kudriavtsev, V.T. and G.K. Urazalieva. (2011). The prerequisites of personality growth in develop mental education. Journal of Russian and East European Psychology, 49(6), 64-83.
3. Nishimoto, Y. (2013). Vertex psychology: From self–consciousness to personality growth. The Proceedings of the 14th L. S. Vygotsky International Readings, Vol. 1, 68-71. Moscow.
4. Nishimoto, Y. (2012). More voices!: Towards the enrichment of Vygotsky’s obuchenie. A paper presentation at the 2nd Estoril Vigotsky conference. Estoril: Portugal.
5. Vygotsky, L.S. (1929/1988). Concrete human psychology. Soviet Psychology, 27, 53-77.
6. Vygotsky, L.S. (1930–1931/1998). Pedology of the adolescent. In Rieber, R. W. (ed.), The Collected Works of L. S. Vygotsky, Vol. 5. New York: Plenum Press.
7. Vygotsky, L.S. (1931/1997). The history of the development of higher mental functions. In Rieber, R.W. (ed.), The Collected Works of L.S. Vygotsky, Vol. 4. New York: Plenum Press.
8. Vygotsky, L.S. (1933/1997). The problem of consciousness. In Rieber, R.W. & Wollock, J. (eds.), The Collected Works of L. S. Vygotsky, Vol. 3. New York: Plenum Press.