For the lateral sweep, the impact of the joint's stiffness variation on  the force peak prominence distribution is not as significant as for the longitudinal sweeps. This results in  the fact that the haptic information gain is not sufficient to distinguish the depth of a nodule. However, the  stiffness can be chosen to facilitate the detection of a nodule. In contrast, for the longitudinal sweeps, the  haptic information gain from one depth to another is significant and helps to determine which stiffness is 