Both haptic and visual senses play a role in how we explore our environment. Previous studies have shown that vision plays a very strong role in perception of object stiffness, yet quantification of the contributions of both haptic and visual feedback remains elusive. This study uses a behavioral adaptation approach in order to better understand how humans perceive stiffness. Namely, subjects make targeted reaches across a virtual surface of varying stiffness, adapting to the new environment. The hand's cursor position is visually distorted to seem more stiff for one group, less stiff for another, and no distortion for the control group. Area Reaching Deviation (ARD) and post-adaptation interface forces, used in previous studies, were the two outcome measures used to determine differences between groups. We compare the slopes of the post-adaptation force-stiffness relations to quantify the effect of visual distortion. Our results indicate that making a stiff surface look more compliant has a greater effect on humans than making a compliant surface look more stiff.