The idea behind squish is that it causes a violent "squirt" of air/fuel mix as the piston squeezes up to the head at TDC. This should improve mixing, combustion, and cooling of potential hot spots, allowing higher CR's. The only problem I have with the theory comes from my experience with old Hemi's, they have no squish area at all, and can run on much worse gas than anything else I ever saw and never detonate. Just one more case of the real world defying theory, I guess.