Finger size has nothing to do with touchscreen accuracy, or touch sensing with modern devices. But fingers, hands and thumbs are opaque, and can get in the way. Since we shift our grip, and use different devices, where are fingers and thumbs are varies so it’s hard to plan that specifically.

This also influences how we gesture. Users will scroll by dragging along the middle of the screen—no surprise there—but only when they will not cover content. When your selectable list has long labels, people scroll to the far right to get to the most empty area they can. And for Arabic or Hebrew, right-to-left languages, the opposite is true.

Always provide room to make sure that touch targets can be seen, enough room to see the clicked state when the target is selected, and try to provide room for users to feel comfortable scrolling.

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