This chapter and the next one consider how to account for the astonishing difference in intelligence between humans and our nearest living ancestors, the great apes. An integrated system that includes the dorsal prefrontal cortex and the parietal association cortex is activated when subjects attempt tests of non-verbal intelligence. It has been suggested that this system might act as a ‘multiple-demand system’ or ‘global workspace’ that can deal with any problem. However, closer examination suggests that the tasks used to support this claim have in common that they involve abstract sequences. These problems can be solved by visual imagery alone. But humans also have the advantage that they also have access to a propositional code. This means that they can solve problems that involve verbal reasoning, as well as being able to form detailed plans for the future. They can also form explicit judgements about themselves, including their perceptions, actions, and memories, and this means that they can represent themselves as individuals. The representation of the self depends in part on tissue in the medial prefrontal cortex (PF).
