This is one of the earliest and still one of the best introductions to socio-historical psychology, the study of how individual human intelligence develops in interaction with people and the environment. In concert with many contemporary approaches in cognitive science today, Lev Vygotsky, A.R. Luria and A.N. Leontiev argued that human intelligence is characteristically mediated through objects and social activity. Humans think through tools. Talking to oneself, for example, is not an irrelevant activity. Putting one's actions into speech is a way of focusing one's consciousness on the problem. This kind of speech is not pointless, but rather a cognitive tool that gives one a greater awareness of one's own actions and makes it easier to modify these actions--a point that Vygotsky proved with research on how children solved problems. Much of human activity involves making use of tools, signs, and activities, the kinetic melodies of action and conceptualization that make us smart, and through which we are able to accomplish the uniquely human feats of complex intellectual action. This is an excellent place to begin studying Vygotsky and activity theory. If you like this you will also like A.R. Luria's *The Making of Mind*, and the classics *The Man With A Shattered World* and *The Mind of a Mnemonist*, the books that inspired Oliver Sacks' writing.