From the real-life experience department: It is very hard to spear food with plastic forks. You stick the fork in the piece of food and lift and the food falls right off. Especially noticeable with, say, pieces of fruit or things like green beans. I assume this is because of the taper of the tines and the very slick, smooth surface of the plastic.

Borrowing a bit from the ring-shank nail used in construction, I think the following design could remedy the slippery plastic fork.

If the tines of the fork have a cross-hatch, ridged, or ribbed texture added to their inside edges, the added grip of the texture better allows the tines to reliably hold the food as it travels from the dish to the mouth; better withstanding the acceleration as you lift the fork away from the dish and better overcoming the inertia of the dish-bound piece of food. Adding the texture only to the inside edges results in the fork feeling the same as a normal smooth-tined fork to the user's mouth and teeth.