Haptically Perceived Softness Of Deformable Stimuli Can Be Manipulated By Applying External Forces During The Exploration

The perception of softness is the result of the integration of information provided by multiple cutaneous and kinesthetic signals. The relative contributions of these signals to the combined percept of softness was not yet addressed directly. We transmitted subtle external vertical forces to the exploring human finger during the exploration of deformable silicone rubber stimuli to dissociate the force estimates provided by the kinesthetic signals and the efference copy from cutaneous force estimates. This manipulation introduced a conflict between the cutaneous and the kinesthetic/efference copy information on softness. We measured Points of Subjective Equality (PSE) of manipulated references to stimuli which were explored without external forces. PSEs shifted as a linear function of external force in predicted directions - to higher compliances with pushing and to lower compliances with pulling force. We found relative contribution of kinesthetic/efference copy information to perceived softness being 23% for rather hard and 29% for rather soft stimuli. Our results suggest that an integration of the kinesthetic/efference copy information and cutaneous information with constant weights underlies softness perception. The kinesthetic/efference copy information seems to be slightly more important for the perception of rather soft stimuli. Metzger, A., & Drewing, K. (2015). Haptically perceived softness of deformable stimuli can be manipulated by applying external forces during the exploration. In World Haptics Conference (WHC), 2015 IEEE (pp. 75-81). IEEE. The Zip file contains all data relative to the publication. The data of each participant is contained in a separate folder. This folder contains a *.raw file for each session of the experiment and a "data" folder, which contains movement trajectories (*.trj files) and the staircase reversals for each condition (*.pse files) in separate folders for each session. A description of the variables is contained in the file VARIABLE_CODES.txt柔软感知是多类皮肤觉与动觉信号所传递信息的整合结果。上述信号对柔软综合感知的相对贡献，此前尚未得到直接探讨。在被试探索可变形硅橡胶刺激物的过程中，我们向其探索用的手指施加微弱的外部垂直作用力，以此分离动觉信号给出的力估算值，与源自皮肤觉力估算的传出副本（efference copy）信号。该操作会在柔软感知相关的皮肤觉与动觉/传出副本信息之间引入冲突。我们测定了经操纵的参照刺激与无外力探索的目标刺激之间的主观相等点（Points of Subjective Equality, PSE）。主观相等点会随外部作用力的大小呈线性变化，且变化方向符合预期：施加推力时，主观相等点向更高柔度偏移；施加拉力时，则向更低柔度偏移。我们发现，对于偏硬的刺激物，动觉/传出副本信息对柔软感知的相对贡献为23%；对于偏软的刺激物，该贡献为29%。本研究结果表明，以固定权重整合动觉/传出副本信息与皮肤觉信息，是柔软感知的底层机制。动觉/传出副本信息对于偏软刺激物的感知，似乎略微更为重要。 Metzger A, Drewing K. (2015). 探索过程中施加外力可操纵可变形刺激的触觉柔软感知. 见：2015 IEEE世界触觉会议（World Haptics Conference, WHC）. 75-81. IEEE. 该压缩包包含本研究相关的全部数据。每位被试的数据均存储于独立文件夹中。每个独立文件夹包含实验各阶段对应的*.raw文件，以及一个名为"data"的子文件夹；该子文件夹按实验阶段分别创建子目录，存储各实验条件下的运动轨迹数据（*.trj文件）与阶梯法反转数据（*.pse文件）。 变量说明详见VARIABLE_CODES.txt文件。