Assessor teaching and the development of the capacity to innovate and to imitate.

Human beings have generated a system of cumulative cultural learning with great adaptive value. The evolution of this system required an increase in the capacity to innovate and to imitate in hominin lineage. However that development is costly and, moreover, imitation may restrain the adaptive advantage of a greater investment on innovation. We suggest that a possible way to overcome this problem in hominin evolution was parental teaching by evaluative feedback - i.e. assessor teaching. To explore this hypothesis we developed a mathematical model of cumulative cultural learning. We consider two cognitive levels, one Basic, with less ability to imitate and innovate, and the other Smart, with more ability of both. We study the transition from Basic to Smart in the absence or in presence of teaching. We also study the transition from no teaching to teaching at each cognitive level. We show that the transition to a Smart is easier in a teaching context than in one of only imitation. We also show that the transition to teaching is easier the greater the cognitive level.