 Hi, I'm Yong Jae Yu, a postdoc researcher at McKinney University. This work was done during my Ph.D. study under the supervision of Professor Seung Moon Choi at POSTEC. In this study, we investigated the perception of electro-adhesive friction stimuli, especially in the free exploration context. That was motivated by our previous work, TouchPoro, which allows visually impaired users to take pictures and understand the contents using audio and haptic stimuli. For the design of TouchPoro's haptic interaction, we need some perceptual backgrounds on electro-adhesive friction stimuli. Thus, we set two research questions as follows. The first is about the spatial resolution of two friction components, and the second is about numerosity judgment. With 16 participants, we conducted two experiments to answer these questions. We used an electro-capacitive panel and an IR frame attached to an LCD monitor, providing haptic stimuli and tracking the user's finger tip. A multiple POST-AQ on a computer controls the signal output. The first experiment investigated the gap detection threshold. We used one up-to-down adaptive staircase method. The gap width between two invisible hapting lines was adjusted during the staircase. The results showed that the threshold were about 3 to 5 millimeters with a large deviation. The line width was the only significant factor. There is no difference between the results of sighted and visually impaired participants. The second experiment investigated numerosity judgment. In each trial, 1 to 10 invisible, horizontal or vertical hapting lines were presented on the surface, and the users were asked to count them and answer. We just showed that the participants tended to miss one or more lines if the number of lines exceeded 7. Frequency showed a significant effect, but the scanning direction didn't. There's no difference between sighted and visually impaired participants' results. The results seem to be related to temporal masking. If two or more percepts happen within a very short interval, they affect each other, causing perceptual errors. Here's our takeaway. We investigated the perception of electro-adhesive friction stimuli in a free exploration context. By summarizing our results, we can say it's better to keep the surfaces simple and separate haptic cues over 10 millimeters even in the free exploration context. Thank you.