Here is an amazing excerpt from "The New Rules of Posture" by Mary Bond, pages 122-123. Apparently, the small fingers proper engagement (when holding something) helps with relaxation of the upper body and enhance the connection to the core (tanden)!
``The bones, muscle, and fascia of the underside of the arm link the fourth and fifth fingers to the shoulder blade and spine. This makes the small fingers important contributors to the power behind any action of the hand. In contrast, the thumb and forefingers connect to the part of the forearm that rotates the elbow joint. This makes these fingers better suited for manipulation and follow-through. ...
When we hold things in our hands without fully engaging the fourth and fifth fingers, we lose the stabilizing connection between the hands, shoulder blades, and spine. Lacking this connection, we seek stability with the upper trapezius. This leads to the all-too-familiar sensations of neck and upper shoulder tension. It also sabotages the relationship to the abdominal corsets that the serratus can provide.
.... If you energize your little fingers as you handle everyday objects, you can train your shoulders while you're getting things done.''