Electrotactile stimulation through matrix electrodes is a promising technology to restore high-resolution tactile feedback in extended reality applications. One of the fundamental tactile effects that should be simulated is the change in the size of the contact between the finger and a virtual object. The present study investigated how participants perceive the increase of stimulation area when stimulating the index finger using static or dynamic (moving) stimuli produced by activating 1 to 6 electrode pads. To assess the ability to interpret the stimulation from the natural cues (natural decoding), without any prior training, the participants were instructed to draw the size of the stimulated area and identify the size difference when comparing two consecutive stimulations. To investigate if other “non-natural” cues can improve the size estimation, the participants were asked to enumerate the number of active pads following a training protocol. The results demonstrated that participants could perceive the change in size without prior training (e.g., the estimated area correlated with the stimulated area, p < 0.001; ≥ two-pad difference recognized with > 80% success rate). However, natural decoding was also challenging, as the response area changed gradually and sometimes in complex patterns when increasing the number of active pads (e.g., four extra pads needed for the statistically significant difference). Nevertheless, by training the participants to utilize additional cues the limitations of natural perception could be compensated. After the training, the mismatch in the activated and estimated number of pads was less than one pad regardless of the stimulus size. Finally, introducing the movement of the stimulus substantially improved discrimination (e.g., 100% median success rate to recognize ≥ one-pad difference). The present study, therefore, provides insights into stimulation size perception, and practical guidelines on how to modulate pad activation to change the perceived size in static and dynamic scenarios.

通过矩阵电极进行电触觉刺激是一种很有前途的技术，可以在扩展现实应用中恢复高分辨率触觉反馈。应模拟的基本触觉效果之一是手指与虚拟物体之间接触尺寸的变化。本研究调查了参与者在使用通过激活 1 至 6 个电极板产生的静态或动态（移动）刺激来刺激食指时如何感知刺激区域的增加。为了评估从自然线索（自然解码）解释刺激的能力，在没有任何事先训练的情况下，参与者被要求绘制刺激区域的大小，并在比较两个连续刺激时识别大小差异。为了调查其他“非自然”线索是否可以改善尺寸估计，参与者被要求按照训练方案枚举活动垫的数量。结果表明，参与者无需事先训练即可感知尺寸变化（例如，估计面积与刺激面积相关，p  < 0.001；≥ 两个垫差异识别成功率 > 80%）。然而，自然解码也具有挑战性，因为当增加活动垫的数量时，响应区域逐渐变化，有时以复杂的模式变化（例如，需要四个额外的垫来实现统计上的显着差异）。然而，通过训练参与者利用额外的线索，自然感知的局限性可以得到补偿。训练后，无论刺激大小如何，激活的垫数和估计的垫数的不匹配都小于 1 个垫。最后，引入刺激的运动大大提高了辨别力（例如，识别≥一垫差异的中位成功率为 100%）。因此，本研究提供了对刺激大小感知的见解，以及如何调节垫激活以改变静态和动态场景中感知大小的实用指南。