For more information: Head, Heart, Belly, Center,
Nine Centers, Centerline, Ground, Sky, Trauma

This beautiful picture shows a perfectly poised head. Balanced freely, directly above the spine, leading the body up and out into space, a clear and far-seeing gaze. Unfortunately rare to see in western cultures!
The main Head functions are:

The Head is oriented to the external world; it is the observation turret; it takes in information and energy from outside; thus both perception, taking in food, and taking in air.

The Head selects the direction to move towards. This is obviously related to the previous point.
The Head gets information from outside as to where to go, and the direction of the Head moves the organism in that direction.
The Head is therefore where understanding, decision and choice take place; thus conceptualization and thought.

Clarity is one of the core qualities of the Head function. Clear understanding, clear decisions

So the head functions are:
External awareness
Receiving
Perceiving
Orientation
Understanding
Abstraction
Deciding, choosing
Direction
Clarity
Wisdom
Going beyond
Spaciousness
Consciousness (Chit)

In the brain, this is the Cortex (primate brain)
 Subjectively, the Head should feel:
open
spacious
light
cool
clear
empty.

This explanation follows on from the model presented on the Evolution page.
The functions of Head, Heart and Belly are derived from this model.
In Qigong practice, the gaze directs the extension of energy.
The meerkat uses its head as observation turret!
Escher's drawing shows the Head as intellect; the conceptual mind contemplating its own identity.