The human (ie ungendered) brain has evolved over countless millennia, with each new structure being laid down over the preceding one. This accounts for some of its major design blunders (resulting in the Kosovo crisis, genital mutilation and padded shoulders). As Koestler pointed out, when a person sets down on Freud's couch it is as though a human being lies down with a crocodile, a horse and a chimpanzee. For the human brain contains the following substructures: brain stem, reptilian brain, mammalian brain, primate brain, homo sap brain.
As everyone knows, all the world's problems (except acne) stem from thinking. Now thinking began in the stem of the brain, an early structure we share with some not-so-developed (but un-warlike) life forms such as tapeworms. Yet the brain stem is where the rot starts, for it is the seat of the most basic instincts: pleasure in men, and obligations in women. The obligations that are ever on a woman's mind are household chores, whereas men seek pleasure wherever they can get it.
The brain stem contains the primitive roots of mentation, manifesting unconscious behaviour and phylogenetic determinism. Despite this, male-female differences are as sharply defined here as elsewhere in the mental hierarchy. A background in physics helps. First the female side:
Woman is ruled by the three laws of chore-dynamics: 1) chores can neither be diminished nor removed, but are by their nature indestructible. 2) The moment a chore is finished it immediately sets about becoming unfinished. Even in the (theoretically) possible case where all chores are done, this state of things can only obtain for the smallest quantum of time. 3) It is not possible to reduce a home to a state of absolute cleanliness in a finite number of steps.
The three Newtonian laws of masculinity are: 1) A male body continues in a state of inertia unless acted upon by a female force. 2) The male will only change his habits if superior force is applied to him. 3) Any attempt by a female to influence a male will cause an opposite reaction of equal strength.
Our most basic fears arise in the unconscious, which the stem is. Thus a woman's deepest fear is that the Queen of England will swoop at midnight to inspect her bathroom, finding it less than royally clean. A man's deepest fear is that the stem of his brain, aka The Head Below, will fall into a coma (ie impotence).
The first structure to crawl out of the stem was the reptilian brain. Due to its murky ancestry it is in both sexes mainly concerned with fears and appetites: dirt detection/removal and sweets in females, sex and inebriation in males. Note that the male penchant for life-threatening activities centres on sex and alcohol, while female neurotic fears focus on dirt and chocolate. To put it simply, both sexes are obsessed with filth, only of a different kind.
Millions of centuries later the mammalian brain evolved. Due to its greater intellectual potential this is dominated by TV sports addiction in males and the nesting instinct in females. A crucial, though small structure operating at this level is the biological alarm clock in females and the Hair Loss Module in males.
Nearing the top of the mental hierarchy, we come to the primate brain. Here gadget mania is preponderant in males and shoe shopping in females. Note also how male and female libido operate divergently.
Finally, at the highest level reached by carbon-based intelligence, there is the specifically human add-on. Here we encounter the need to improve the partner in females, and the corresponding structure that evolved in response to it in males, the nag filter. Notice also the difference of emphasis in the communication module, shown at far left.
It is noteworthy that time and space are perceived differently by the two sexes. Witness the clock module (womb use-by-date vs hair loss in progress) and the "I am too fat" obsession vs the Small Dick Syndrome.
Not shown in the diagram is the corpus callosum, which connects the two hemispheres of a brain. In females this allows multi-tasking, in males it causes drink-driving. My friend Napier cleared up a mystery for me, pointing out that it is not true that men cannot multi-task. About 60-70% of their brain is occupied at all times with thoughts of sex.