Integration of serial sensory information in haptic perception of softness.

Abstract

Redundant estimates of an environmental property derived simultaneously from different senses or cues are typically integrated according to the maximum likelihood estimation model (MLE): Sensory estimates are weighted according to their reliabilities, maximizing the percept's reliability. Mechanisms underlying the integration of sequentially derived estimates from one sense are less clear. Here we investigate the integration of serially sampled redundant information in softness perception. We developed a method to manipulate haptically perceived softness of silicone rubber stimuli during bare-finger exploration. We then manipulated softness estimates derived from single movement segments (indentations) in a multisegmented exploration to assess their contributions to the overall percept. Participants explored two stimuli in sequence, using 2-5 indentations, and reported which stimulus felt softer. Estimates of the first stimulus's softness contributed to the judgments similarly, whereas for the second stimulus estimates from later compared to earlier indentations contributed less. In line with unequal weighting, the percept's reliability increased with increasing exploration length less than was predicted by the MLE model. This pattern of results is well explained by assuming that the representation of the first stimulus fades when the second stimulus is explored, which fits with a neurophysiological model of perceptual decisions (Deco, Rolls, & Romo, 2010). (PsycINFO Database Record

The Effect of Between-Probe Variability in Haptic Feedback on Stiffness Perception and Grip Force Adjustment

“…Specifically, the Serial Weighted Average Model scored slightly higher than the other two average models. This result is consistent with the results found in the work of Metzger et al [11]. They found that the nervous system attributes decreasing weights to the different stiffness levels based on their serial placement in the probing sequence, with the highest weight given to the stiffness level experienced first and the lowest to the last.…”

“…Serially Weighted Averagebased on [11], in trials in which the comparison force field preceded the standard, unequal weights were attributed to the different stiffness levels, with the highest weight given to the first stiffness level and the lowest to the last stiffness level. On the other hand, if the standard was presented first, all eight stiffness levels were given equal weighting.…”

“…Kuschel et al [6] modified the relation between visual and haptic information, showing that visual-haptic integration in compliance estimation is likely a weighted sum of the visual and haptic sensory inputs. In a study by Metzger et al [11], the researchers manipulated the stiffness of a single probe out of a series of identical multiple probes carried out by each participant. This allowed them to determine that there are cases in which the nervous system integrates serial haptic information as a weighted average.…”

“…Their model attributes decreasing weights to the different stiffness levels based on their serial placement in the probing sequence, with the highest weight given to the stiffness level experienced first and the lowest to the last. With the exception of Metzger et al [11], the integration of haptic information received through multiple interactions with the same object has received little attention in the context of stiffness perception.…”

Processing of haptic texture information over sequential exploration movements

“…This is qualitatively in line with the threshold predictions but was not quantitatively analyzed and thus is not conclusive. Importantly, results from Metzger, Lezkan, and Drewing (2017) are at odds with the prediction of equal weights in the integration of sequential haptic information. The authors investigated softness discrimination, where people typically indent a soft stimulus repeatedly, and determined the weights of indentation-specific softness estimates for the first and the second stimulus in a trial.…”