I have already discussed the anthropological origins of different head shapes, and their relation to personality. There is also a morphological basis. Below is a diagram of the brain.

Neanderthals exhibit an enlarged occipital lobe. This is a visual center. Asians and engineers display higher Neanderthal expression and visuospatial intelligence. I have observed the naive visuo-intellectual and emotional quality of Tx’s (those with Neanderthal back of skull).
Mx’s (Melon back of head) display an enlarged parietal lobe. It is navigational, multisensory, and involved with symbolic intelligence, linguistic and mathematical. It controls e.g. grasping and manipulation of objects with the hands. I have observed the social manipulation oriented motivation of Mx’s.
The next two sections are speculative (even more so than everything else):
The frontal lobe contains most of the dopamine receptors and reaches maturity in one’s 20’s. It controls recognition of future consequences, moral decisions, social conditioning, and analogies. It is a seat of conscience and intelligence.
Wikipedia states: “The frontal lobe is the same part of the brain that is responsible for executive functions such as planning for the future, judgment, decision-making skills, attention span, and inhibition.”
I have a suspicion that increased frontal lobe mass is weakly associated with ethical facility, social grace, and applied life intelligence. Other factors, including overall volume, also count here. A high broad forehead indicates a large frontal lobe. The lobotomy stereotype is suggestive.
The temporal lobe is associated with semantics processing and long term memory. It controls speech and language functions. I’ve seen very limited hints that Starchildren tend to emphasize these processing traits. Extensive semantic processing of long term memory. Read Pavlina to see what I mean. They also tend towards long-term attachments, like Neanderthals. Significantly, the only original Starchild skull ever found was buried in a Romeo and Juliet setting. The diminutive Starchild was buried in a mineshaft, with his skeletal hand placed over the arm of an unburied human female skeleton. It appears that the female first buried her dead half-alien lover, then committed suicide with his hand on her arm.
This represents possibly the most extreme example of emotional imprinting ever recorded, and is reminiscent of ancient Melons buried with their entire households. Perhaps these mass burials were as voluntary as the poignant scene in the mine shaft, undisturbed for 900 years. One is reminded of dogs that lay down and die by their masters’ graves.
I hope this lays to rest the facile accusation that I am resurrecting the ridiculous phrenology practiced hundreds of years ago. The phrenological diagram below has no basis in modern neuroscience, whereas my theory is at least plausible. Damnation by nominal association is a dishonest argumentative tactic.

Lastly, let me state for the dense that these are weak effects that must be evaluated together with other factors to form a complete picture of a person.