 For this reason domain-specific mechanisms are faster and more effective than their domain-general counterparts and we should expect natural selection to have favoured them.The authors conclude that the flexible and highly intelligent appearance of human behaviour is not the result of domain-general mechanisms having taken over from older domain-specific mechanisms (or 'instincts'), but the exact opposite; human domain-specific mechanisms have proliferated to the point where man has become competent in an unprecedented number of domains, and can therefore usually employ some motley assortment of these specialized mechanisms for his own novel needs (e.g.he has combined lingual, visual and motor skills to invent the written word, for which no specialized psychological mechanism exists).