One practical model exemplifying the nature of mental intelligence as an organising and synthesising function is found in the thought of political/military 'intelligence' where organisations have been built up in stages to cope with at least three major levels necessary to arriving at the overall judgements of 'intelligence'. The stages are 1) signals, 2) deciphering, 3) intelligence. The building up of an intelligence network, such as the enormous one developed by the Allies during World War II, involves (1) the registering of a very large volume of radio and other 'signals traffic' (the observations that form the main basis), (2) a painstaking process of decoding (i.e. understanding and relating the content of the recorded signals) as a preliminary to (3) the cross-analysis of their mass for general features and their relation to other relevant sources of knowledge. Even then it remains to draw conclusions from all this information about future action: about the intentions they reveal (on the part of 'the enemy') and to formulate strategies to counteract them where necessary.
For the individual psyche the three stages correspond to (1) perception, (2) interpretation and (3) understanding. Depending upon the very different requirements of the whole environment in which any person lives, the mass of materials or 'data traffic' that must be handled at the basic level and the complexities that 'deciphering' them calls for, some minds remain 'undeveloped' in that they cannot master sufficient organisation at the first or second stages, while even a majority of educated persons may remain incapable of syntheses of a very comprehensive nature at a high level of generality.