A model of perception of the central point of elastic force fields

While exploratory movements are an integral part of the act of perceiving in the haptic modality, little is known about the processes that perform the mental synthesis necessary to gain a unified representation of the object. To address this issue, we investigated the accuracy and precision with which participants could identify the central position of a unidimensional elastic force field. The stiffness of the left and right sides of the force field was separately manipulated. An important characteristic of this task is that an elastic force near the rest point is presumably below the absolute threshold for force perception. In other words, the observer cannot directly identify this position from its sensory apparatus and must somehow extrapolate it. We found that the perceived centers of the force fields were biased toward the weaker side in asymmetric force fields and that the precision of the responses decreased with the strength of the force fields. We present a model of the perception of the central point of these force fields that can explain the observed biases. Future development of the model will aim at providing an account of the variable error.