Wikipedia:Reference desk/Archives/Science/2018 December 9

= December 9 =

Why does my smartphone have such a hard time reading my fingerprints when my sympathetic tone is elevated for long periods or concomitant with an NMDA receptor antagonist?
I don't want medical advice. I'd just like to know the scientific reason why when my sympathetic tone is very high (along with blood pressure and pulse) due to NMDA receptor antagonist use why my smartphone struggles to read my fingerprints. I've observed this phenomenon for about 4 years for about 15-20 such experiences. It refuses to authenticate and I've actually accidentally reset my phone this way due to security measures. I've tried to make my phone recognize an alternate set of fingerprints, but it turns out I have almost no trainable fingerprints at all in this elevated physiological state! Why? When my physiological state returns to normal (about 12-36 hours) my phone recognizes my fingerprint again, so this is a fairly long recovery process. My hypothesis is that acute dehydration leads to blurring of the fingerprint ridges. Am I correct? Yanping Nora Soong (talk) 01:29, 9 December 2018 (UTC)

Also, I just read this article -- would the following causes: high blood pressure + vasoconstriction + hypovolemia + electrolyte imbalance + skin becoming cold due to activation of the fight or flight response for 6-24 hours at a time -- lead to a fingerprint capacitance signal outside the range of most fingerprint readers? Yanping Nora Soong (talk) 01:36, 9 December 2018 (UTC)
 * Most likely it's a combination of sweaty skin (increased sympathetic tone increases sweating) and the effects of vasoconstriction changing the elasticity, etc. of the skin. My smartphone has been unable to read my fingerprint with damp hands, either from sweat or handwashing. There are many types of fingerprint sensors, but I believe pretty much all smartphones on the market use either optical or capacitive sensors. Damp skin will interfere with both of these, either by blurring the image or changing the skin's electrical conductivity. --47.146.63.87 (talk) 10:22, 9 December 2018 (UTC)


 * As an aside, the term "sympathetic tone" (as linked by the OP above) redirects to Sympathetic nervous system, which uses the term only once without defining what it is. Perhaps someone with expertise in this area could add some clarification there? {The poster formerly known as 87.81.230.195} 90.202.210.56 (talk) 23:26, 9 December 2018 (UTC)
 * It's a qualitative way of referring to the activation of the sympathetic nervous system. The parasympathetic counterpart is vagal tone -- and I suppose vagal tone often dramatically decreases during these experiences as well. Yanping Nora Soong (talk) 03:07, 10 December 2018 (UTC)


 * I don't really know if NMDA receptor antagonists generally affect the sympathetic nervous system, nor can it be assumed that such effects must include sweaty fingers, so it would seem productive to do an empirical test: wash and dry your hands and see if that addresses the issue. If not, it is very possible we might actually have to find out how the sensor works, whether it is affected by vascular flow, whether that flow (or some other measuring mechanism) is affected by the specific drug etc. in order to get anywhere.  Personally I'd say tossing the "smart" phone and relying, as needed, on a burner that never heard of fingerprints and costs $10 to buy and $80 a year to maintain would be the smarter move, but that's just me. Wnt (talk) 14:04, 10 December 2018 (UTC)


 * Even I wipe my fingers (I've observed this for years) and smartphones in general refuse to authenticate me until I am no longer tachycardic again and my vitals return to baseline (which can take 48-72 hours). I'm pretty sure I have elevated sympathetic tone, exacerbated by anticholinergic effects because emergency department physicians have told me and in fact introduced me to the concept of sympathetic tone and I don't want to discuss any medical details because that would risk making this a medical question. Yanping Nora Soong (talk) 17:59, 11 December 2018 (UTC)
 * For the experiment I suggested "wash and dry" to be sure that salt or other substances are excluded from consideration. But I also have to ask -- does this occur to anyone else?  I mean, there are a lot of agitated people who make phone calls.  If somebody set up a fingerprint reader to "secure" their phone against whoever is so unimportant that they can't compel fingerprints and then that user can't call 911 because they're too frightened, I would laugh and laugh... Wnt (talk) 02:19, 12 December 2018 (UTC)
 * Most phones can call emergency numbers without unlocking. Most phones also have a backup unlock normally via PIN, pattern or password if the person can't use the fingerprint unlock for some reason. Nil Einne (talk) 10:44, 12 December 2018 (UTC)

Unforgettable
What makes riding a bike, swimming, driving unforgettable? I surely see the advantage of it, if you learn how to hunt, you'll keep this knowledge until the new huting season. However, what makes it like that? Are only motor skill in this category? --Doroletho (talk) 17:30, 9 December 2018 (UTC)
 * See Rote learning and Muscle memory. ←Baseball Bugs What's up, Doc? carrots→ 18:35, 9 December 2018 (UTC)


 * Motor learning occurs in the premotor cortex rather than in the hippocampus like many forms of recall. There actually is a short-term form of motor memory, which means that it is not always "unforgettable" (see  for an introduction and  for the article) but we seem to think less about it, I suppose. Wnt (talk) 14:13, 10 December 2018 (UTC)