Memory influences haptic perception of softness

Anna Metzger,Knut Drewing

doi:10.1038/s41598-019-50835-4

Abstract

The memory of an object’s property (e.g. its typical colour) can affect its visual perception. We investigated whether memory of the softness of every-day objects influences their haptic perception. We produced bipartite silicone rubber stimuli: one half of the stimuli was covered with a layer of an object (sponge, wood, tennis ball, foam ball); the other half was uncovered silicone. Participants were not aware of the partition. They first used their bare finger to stroke laterally over the covering layer to recognize the well-known object and then indented the other half of the stimulus with a probe to compare its softness to that of an uncovered silicone stimulus. Across four experiments with different methods we showed that silicon stimuli covered with a layer of rather hard objects (tennis ball and wood) were perceived harder than the same silicon stimuli when being covered with a layer of rather soft objects (sponge and foam ball), indicating that haptic perception of softness is affected by memory.

Highlights

Our perception of the environment is not solely determined by its physical properties but can be partially modulated top-down
Influences of prior knowledge have been reported for heaviness perception: A small object feels heavier than a large one with the same weight and an object made of polystyrene is perceived heavier than an object with the same weight but made of lead[20,21,22,23,24]
For an intensive object property like softness, built up knowledge likely relates exclusively to softness so that a direct link can be made between prior knowledge about softness and its perception, allowing us to generalize the effect of prior knowledge on perception from visual[12,14,15] to haptic perception

Summary

Introduction

Our perception of the environment is not solely determined by its physical properties but can be partially modulated top-down. These effects demonstrate that stimuli with the same physical colour properties are perceived differently depending on prior knowledge of their typical colour Such influence of typical, remembered colours of objects on the perception of their colours could be successfully predicted assuming Bayesian integration of information[17], a model of optimal combination of evidences from multiple sources[18,19]. A recent study on the influence of weight expectations for every-day objects suggested a perceptual shift away from the object’s typical weight in a first experiment, but towards it in the second experiment[32] These findings demonstrate that the mechanisms of how expectations and prior assumptions influence perceived heaviness are far from being understood. For an intensive object property like softness, built up knowledge likely relates exclusively to softness so that a direct link can be made between prior knowledge about softness and its perception, allowing us to generalize the effect of prior knowledge on perception from visual[12,14,15] to haptic perception

Objectives

Methods

Results

Conclusion