Up or down ?

If you want to stop your bike from tending to run wide as you accelerate around and out of corners, should you stiffen the rear suspension to reduce squat, or should you soften the rear suspension to increase squat ? I was watching a video the other day where a rider complained about the bike running wide in corners, so they increased the preload on the rear suspension to increase the ride height at the rear of the bike, which seemed to achieve nothing.