The follow the leader and interpersonal goal integration models cannot replicate the hard and soft interactions.

<p>(A) Prediction of the improvement and interaction effort from the <i>follow the leader</i> model, where subjects switch to following the partner’s cursor if they are nearest to the target. The prediction overestimates the interaction effort by a large amount, and greatly underestimates the performance improvement. (B) Predictions from the <i>interpersonal goal integration</i> model, where the visual and haptic information of the target are combined to yield a better prediction of the target’s motion. The haptic estimate of the target is obtained by forming a representation of the partner that identifies how the partner’s movement changes in response to the motion of the target, which is used to estimate the partner’s target. Unlike the data, this model does not exhibit any modulation in the improvement due to the coupling stiffness.