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If I place a ring on the screen of my phone, and then try to scroll with my finger inside the ring, the ring and my finger move up and down, but the screen doesn't scroll. If I leave the ring on the screen, but put my finger to one side of it, it does scroll.

I've repeated thing with several rings, and have observed that if the ring touches the screen at every point around it, scrolling doesn't work. If the ring doesn't touch the screen all the way around (either because it's shaped, or has a large stone) my phone will still scroll.

These results are consistent with both gold and silver rings.

Can anybody explain why this is? I think I understand the theory behind capacitive touch screens (which is what my phone has) but I can't understand why the metal would only have an adverse effect when it completely surrounds my finger.

The above was seen on my phone (iPhone SE 2020), but my Kindle Fire tablet doesn't display the same behaviour, nor does a Huawei mediapad. I don't want to complicate it too much though, so I don't need to know why it doesn't happen on the tablets, just why it does on the particular type of screen the iPhone has.

BeginTheBeguine
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  • Not all screens work the same way, so I don't even know if the phenomena you describe are universal. Some use your finger's pressure, others its heat, to say nothing of biometric criteria. – J.G. Sep 16 '21 at 18:37
  • Verified the behavior on an iPhone SE. https://itstillworks.com/kind-touch-technology-iphone-use-18254.html | https://en.wikipedia.org/wiki/Touchscreen#Capacitive – Solomon Slow Sep 16 '21 at 18:46
  • The Kindle display works on different principles so there is no reason to expect the same behavior. – nasu Sep 16 '21 at 22:55
  • @Nasu, I just approached it like any experiment, trying a wide range of screens and rings. I noticed it on my phone, then tried a Kindle Fire, and a Huawei mediapad with six different rings. My 'normal' Kindle is so old isn't actually touchscreen! My mum tried her iPhone and is going to ask my grandma to try on her Kindle Paperwhite tomorrow. My sister is going to check her iPad in the morning. I asked my brother if he could try his iPad too, but he doesn't have any rings and his girlfriend was asleep so he couldn't borrow hers. But in the morning I'll have more results! – BeginTheBeguine Sep 16 '21 at 23:02
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    I applaud your experimental initiative. However, this particular experiment will yield confusing and contradictory results, with different devices exhibiting different behavior. You might classify different devices according to the results of your experiment without understanding why they fit into distinct categories; later, you will understand this as being due to the fact that screens operate via different mechanisms (e.g. pressure vs capacitive sensing). If you throw in several decades of confusion and skepticism of others’ experiments, that’s a pretty good allegory for real science. – J. Murray Sep 16 '21 at 23:11
  • @J.Murray I just want the iPhone result explained to me. I'm perfectly happy with "The others have a different type of screen, so this doesn't apply" for the rest. – BeginTheBeguine Sep 16 '21 at 23:45

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