The distances between pairs of tactile stimuli oriented across the width of the hand dorsum are perceived as about 40% larger than equivalent distances oriented along the hand length. Clear anisotropies of varying magnitudes have been found on different sites on the limbs and less consistently on other parts of the body, with anisotropies on the center of the forehead, but not on the belly. Reported anisotropies on the center of the forehead, however, might reflect an artefact of categorical perception from the face midline, which might be comparable to the expansion of tactile distance perception observed for stimuli presented across joint boundaries. To test whether tactile anisotropy is indeed a general characteristic of the tactile representation of the face, we assessed the perceived distance between pairs of touches on the cheeks and three locations on the forehead: left, right, and center. Consistent with previous results, a clear anisotropy was apparent on the center of the forehead. Importantly, similar anisotropies were also evident on the left and right sides of the forehead and both cheeks. These results provide evidence that anisotropy of perceived tactile distance is not a specific feature of tactile organization at the limbs but it also exists for the face, and further suggest that the spatial distortions found for tactile distances that extend across multiple body parts are not present for stimuli that extend across the body midline.

沿手背的宽度定向的成对触觉刺激之间的距离被认为比沿手长度定向的等效距离大约40％。在四肢的不同部位发现了大小不一的清晰各向异性，而在身体的其他部位则不一致，前额中心处有各向异性，而腹部则没有。然而，在前额中心报告的各向异性可能反映了从面部中线分类感知的假象，这可能与跨关节边界呈现的刺激所观察到的触觉距离感知的可比性相当。为了测试触觉各向异性是否确实是面部触觉表示的一般特征，我们评估了双颊接触和额头三个位置之间的感知距离：左，右和中心。与以前的结果一致，在额头的中央明显有明显的各向异性。重要的是，在前额的左侧和右侧以及两个脸颊上也有类似的各向异性。这些结果提供了证据，即感知触觉距离的各向异性不是四肢触觉组织的特定特征，但对于面部也存在，并且进一步表明，对于跨越多个身体部位的触觉距离发现的空间畸变不存在。整个身体中线的刺激。在前额的左侧和右侧以及两个脸颊上也有相似的各向异性。这些结果提供了证据，即感知触觉距离的各向异性不是四肢触觉组织的特定特征，但对于面部也存在，并且进一步表明，对于跨越多个身体部位的触觉距离发现的空间畸变不存在。整个身体中线的刺激。在前额的左侧和右侧以及两个脸颊上也有相似的各向异性。这些结果提供了证据，即感知触觉距离的各向异性不是四肢触觉组织的特定特征，但对于面部也存在，并且进一步表明，对于跨越多个身体部位的触觉距离发现的空间畸变不存在。整个身体中线的刺激。