Humans are unique among earthly creatures. Language is one of the areas where we have no peers among the animals. The other is the ability to design and complex structures (excluding stuff like bird nests, based upon instinct, not reason).

There are two areas of the brain that process language directly. (Of course, they connect to other areas that process it indirectly.) These areas are associated with speech (Broca's Area) and hearing (Wernicke's Area), respectively (Functions are actually more distributed than this simple model).

The job of the speech center is to take thoughts and apply rules of grammar to them to convert them into speech. The rules of grammar are highly variable, but the way that they are applied is not, but is the same in all languages. The speech center constructs grammatical trees whose nodes it populates with the appropriate speech particles. It then "unwinds" this tree into a linear output string which results (after further processing), in speech.

The job of the hearing center is the reverse of the previous. It takes in a linear input string of sound signals and breaks them up into language particles, which it then assembles into a tree which is (hopefully) congruent to the tree constructed in the speech area of the speaker's brain.

I notice a relationship here between these two areas and the two forms of reasoning: Deductive and Inductive.

The former applies rules to data (thoughts) to obtain results resulting in speech. It seems to me that this is similar to the process by which rules are applied to hypotheses to yield conclusions.

The latter seeks to match the results (of previous speech) to the previously constructed rules (or additional rules if needed), by trial and error, until a coherent structure can be produced. It seems to me that this is similar to the process whereby information from the environment is analyzed into generalizations.

It is important to note that the language functions are highly concentrated in the dominant (usually left) half of the brain. Yet the brain is symmetric in overall structure. Therefore, the question naturally arises: "What do the opposite counterparts of the speech and hearing centers do?"

My hypothesis is that they perform the analagous functions of their linguistic counterparts with symbols that represent objects rather than words. Thus, IMHO, the opposite counterpart of the speech center manipulates symbols of external objects. For example: One sees several bricks. This part of the brain puts one brick on top of each other symbolically to form a structure such as a building. Then the person can actually construct such a building.

Similarly, the opposite of the hearing center generalizes the properties of external objects and the rules by which external objects behave. This is homologous to analysis of speech and the development of rules of interpretation.

If I am correct, then both deductive and inductive reasoning are built-in to the human brain at a fundamental level.