# Polydactylism **URL:** \ **Category:** Factual Questions\ **Created:** [December 17, 2022, 2:31am UTC](https://boards.straightdope.com/t/polydactylism/976687 "2022-12-17T02:31:01Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Deflagration](https://avatars.discourse-cdn.com/v4/letter/d/3ab097/32.png) [@Deflagration](https://boards.straightdope.com/u/Deflagration)\ **Post date:** [December 17, 2022, 2:31am UTC](https://boards.straightdope.com/t/polydactylism/976687/1 "2022-12-17T02:31:01Z")
Some, if not most of us, have four fingers and a thumb. I have questions regarding those that have more than this: 1. Due to routing of tendons etc. Most of us (quintdactyal(?) folkes) **can’t** move our little finger without it also moving our ring finger. Is this universal. Does the little finger automatically affect the one next to it. 2. I’m guessing “it depends” - Some fingers may be residual but do Polydactyls have independent movement. Duplicated Muscles - Duplicated tendons - Duplicated nerve pathways (both movement and independent touch etc)? ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [December 17, 2022, 2:49am UTC](https://boards.straightdope.com/t/polydactylism/976687/2 "2022-12-17T02:49:35Z")
_Most_ cases of polydactyly are vestigial with a few that are more fully formed but still non-functional. I see them commonly hanging off the little finger, and a few times as a partly duplicated thumb or Great Toe. But there are rare cases of functional supernumerary digits, even if I’ve never seen it. Here’s a case report of a mother son dyad with functional bilateral supernumerary fingers between thumb and index finger. [https://www.nature.com/articles/s41467-019-10306-w](https://www.nature.com/articles/s41467-019-10306-w) They report that there is even brain space devoted to the fingers. One presumes that the real estate is taken from some other motor function … ---
**Author:** ![susan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/susan/32/17537_2.png) [@susan](https://boards.straightdope.com/u/susan)\ **Post date:** [December 17, 2022, 3:34am UTC](https://boards.straightdope.com/t/polydactylism/976687/3 "2022-12-17T03:34:35Z")
> [@DSeid](#): > > One presumes that the real estate is taken from some other motor function Like counting to 5? While my little fingers move somewhat in tandem with my ring fingers, I have no trouble moving them independently. ---
**Author:** ![puzzlegal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puzzlegal/32/3827_2.png) [@puzzlegal](https://boards.straightdope.com/u/puzzlegal)\ **Post date:** [December 17, 2022, 3:49am UTC](https://boards.straightdope.com/t/polydactylism/976687/4 "2022-12-17T03:49:14Z")
> [@susan](#): > > While my little fingers move somewhat in tandem with my ring fingers, I have no trouble moving them independently. Ditto. Independent forward and back motion is easy. Independent side to side motion is harder, but i can do it. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [December 17, 2022, 4:03am UTC](https://boards.straightdope.com/t/polydactylism/976687/5 "2022-12-17T04:03:29Z")
If you can both fully flex your little finger without your ring finger moving we have a very unusual group of people here. It is generally accepted that such does not typically occur. The following article is an attempt to parse out how much of that standard lack of full independence is mechanical coupling and how much limitation imposed by neuromuscular control. Spoiler: It depends on the finger. > **[Human Finger Independence: Limitations due to Passive Mechanical Coupling...](https://journals.physiology.org/doi/full/10.1152/jn.00480.2004)** > > We studied the extent to which mechanical coupling and neuromuscular control limit finger independence by studying passive and active individuated finger movements in healthy adults. For passive movements, subjects relaxed while each finger was... ---
**Author:** ![susan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/susan/32/17537_2.png) [@susan](https://boards.straightdope.com/u/susan)\ **Post date:** [December 17, 2022, 4:06am UTC](https://boards.straightdope.com/t/polydactylism/976687/6 "2022-12-17T04:06:07Z")
Well, I did practice various Vulcan and related hand gestures as an early adolescent, and also taught myself to raise each eyebrow independently… ---
**Author:** ![AHunter3](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ahunter3/32/368_2.png) [@AHunter3](https://boards.straightdope.com/u/AHunter3)\ **Post date:** [December 17, 2022, 5:55am UTC](https://boards.straightdope.com/t/polydactylism/976687/7 "2022-12-17T05:55:21Z")
I bet they play a mean piano… ---
**Author:** ![susan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/susan/32/17537_2.png) [@susan](https://boards.straightdope.com/u/susan)\ **Post date:** [December 17, 2022, 6:19am UTC](https://boards.straightdope.com/t/polydactylism/976687/8 "2022-12-17T06:19:31Z")
[![](https://metode.org/wp-content/uploads/2021/11/Gattaca_pianist.jpg) ](https://metode.org/wp-content/uploads/2021/11/Gattaca_pianist.jpg) _Gattaca_ ---
**Author:** ![puzzlegal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puzzlegal/32/3827_2.png) [@puzzlegal](https://boards.straightdope.com/u/puzzlegal)\ **Post date:** [December 17, 2022, 12:53pm UTC](https://boards.straightdope.com/t/polydactylism/976687/9 "2022-12-17T12:53:21Z")
> [@DSeid](#): > > If you can both fully flex your little finger without your ring finger moving we have a very unusual group of people here Fully flex? Like curl it to the palm? No. But holding it straight, i can move it forward and back, it and side to side, without moving the ring finger. Curiously, i can curl the other three fingers independently. Now i need to see if i can learn a new trick… ---
**Author:** ![solost](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/solost/32/11776_2.png) [@solost](https://boards.straightdope.com/u/solost)\ **Post date:** [December 17, 2022, 1:05pm UTC](https://boards.straightdope.com/t/polydactylism/976687/10 "2022-12-17T13:05:07Z")
> [@DSeid](#): > > Here’s a case report of a mother son dyad with functional bilateral supernumerary fingers between thumb and index finger. > [@AHunter3](#): > > I bet they play a mean piano… …or totally rip a guitar solo! > [@DSeid](#): > > If you can both fully flex your little finger without your ring finger moving we have a very unusual group of people here I just checked and I can move both little fingers in all directions and curl and flex independently of my ring fingers. Is it really all that unusual? Speaking of guitar, I do play, though amateurly. Maybe that helps? ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [December 17, 2022, 2:29pm UTC](https://boards.straightdope.com/t/polydactylism/976687/11 "2022-12-17T14:29:03Z")
> [@solost](#): > > Is it really all that unusual? Yes that is my understanding, to some degree just because of how the tendons cross connect. Please note the phrase is completely independently. Fully flexing the little finger to palm without the ring finger moving at all, or fully move the little finger to the side as far as it goes without the ring finger following it some. Only moving a small range, or the other finger only moving a small bit, is not complete independence. ---
**Author:** ![puzzlegal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puzzlegal/32/3827_2.png) [@puzzlegal](https://boards.straightdope.com/u/puzzlegal)\ **Post date:** [December 17, 2022, 2:34pm UTC](https://boards.straightdope.com/t/polydactylism/976687/12 "2022-12-17T14:34:33Z")
It’s certainly possibly to do it. Right now i am holding my phone with the ring and middle finger on one side, and the thumb and palm on the other. And with the ring finger held in place, it’s easy to move my little finger around, in almost it’s full range of motion. I can even bring it to the palm. But if i try to flex the joint closest to the fingernail, i have to be very careful, or everything cramps. (I can do it, but if i move in the wrong order it’s unpleasant.) I mean, does moving one finger tend to tug another because they are connected? Yes. Does that mean it can’t be done? No. Oh, interesting. My left pinky has a much smoother and more controlled motion than my right pinky. ---
**Author:** ![solost](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/solost/32/11776_2.png) [@solost](https://boards.straightdope.com/u/solost)\ **Post date:** [December 17, 2022, 3:23pm UTC](https://boards.straightdope.com/t/polydactylism/976687/13 "2022-12-17T15:23:23Z")
> [@puzzlegal](#): > > Oh, interesting. My left pinky has a much smoother and more controlled motion than my right pinky. I can move my right little toe outward independent of my next (ring?) toe, but my left little toe I can not move independently at all. Always though that was weird that it wasn’t bisymmetrical. ---
**Author:** ![purplehorseshoe](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/purplehorseshoe/32/2996_2.png) [@purplehorseshoe](https://boards.straightdope.com/u/purplehorseshoe)\ **Post date:** [December 17, 2022, 3:30pm UTC](https://boards.straightdope.com/t/polydactylism/976687/14 "2022-12-17T15:30:47Z")
> [@puzzlegal](#): > > And with the ring finger held in place, it’s easy to move my little finger around Holding the other finger still is “cheating” here; the point trying to be made is that the tendons are connected so that if the ring finger _isn’t_ being held still by an outside influence, it will move along with the pinky. ---
**Author:** ![P-man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/p-man/32/3606_2.png) [@P-man](https://boards.straightdope.com/u/P-man)\ **Post date:** [December 17, 2022, 3:33pm UTC](https://boards.straightdope.com/t/polydactylism/976687/15 "2022-12-17T15:33:55Z")
> [@puzzlegal](#): > > Oh, interesting. My left pinky has a much smoother and more controlled motion than my right pinky. Same here. In my case it may be from decades of playing Piedmont style blues, which requires me to stretch my pinky to go down the fretboard. ---
**Author:** ![Die\_Capacitrix](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/die_capacitrix/32/9_2.png) [@Die\_Capacitrix](https://boards.straightdope.com/u/Die_Capacitrix)\ **Post date:** [December 18, 2022, 8:40am UTC](https://boards.straightdope.com/t/polydactylism/976687/16 "2022-12-18T08:40:48Z")
> [@susan](#): > > While my little fingers move somewhat in tandem with my ring fingers, I have no trouble moving them independently. I can only do this when my ring finger is curled. If my ring finger is extended, my pinky finger will move as well. > [@susan](#): > > Well, I did practice various Vulcan and related hand gestures as an early adolescent, and also taught myself to raise each eyebrow independently… Vulcan hand gestures: check Only right eyebrow, though. I also played violin (from 9 - 17), so there is some extra training for each pinky. ---
**Author:** ![needscoffee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/needscoffee/32/1076_2.png) [@needscoffee](https://boards.straightdope.com/u/needscoffee)\ **Post date:** [December 18, 2022, 6:06pm UTC](https://boards.straightdope.com/t/polydactylism/976687/17 "2022-12-18T18:06:25Z")
> [@purplehorseshoe](#): > > Holding the other finger still is “cheating” here; the point trying to be made is that the tendons are connected so that if the ring finger _isn’t_ being held still by an outside influence, it will move along with the pinky Yes, thank you! It’s not difficult to do when the other fingers are braced against an object or each other. Doing it it with the hand held in mid-air, without any other fingers touching each other or anything else is what’s being asked about. ---
**Author:** ![susan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/susan/32/17537_2.png) [@susan](https://boards.straightdope.com/u/susan)\ **Post date:** [December 18, 2022, 6:33pm UTC](https://boards.straightdope.com/t/polydactylism/976687/18 "2022-12-18T18:33:55Z")
The clarification helps, thanks. ---
**Author:** ![Eyebrows\_0f\_Doom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eyebrows_0f_doom/32/3119_2.png) [@Eyebrows\_0f\_Doom](https://boards.straightdope.com/u/Eyebrows_0f_Doom)\ **Post date:** [December 18, 2022, 6:43pm UTC](https://boards.straightdope.com/t/polydactylism/976687/19 "2022-12-18T18:43:00Z")
> [@DSeid](#): > > or fully move the little finger to the side as far as it goes without the ring finger following it some. Like the Vulcan thing but between the little & ring fingers? This seems trivially easy to do. 🤔 ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [December 18, 2022, 7:27pm UTC](https://boards.straightdope.com/t/polydactylism/976687/20 "2022-12-18T19:27:32Z")
I think I must be failing to explain what independent movement is that so many here are believing they can do what is documentably … not common. Anyway. The OP was more about functional polydactyly. I may weird (okay, independent of this, I am) but I think that kindred with bilateral functional fingers between their index and thumbs is very interesting to consider. I am a bit frustrated that the report was not more complete. There is a huge chunk of brain real estate devoted to both sensory and motor control of the thumb and index fingers. Did the region devoted to control of those supernumerary digits cannibalize from that region, did the real estate devoted to the hand overall enlarge, harvesting from something else? Did the region become more active and functionally more densely packed? I know it’s not quite the same thing but it makes think of this as a connection- > **[Functional connectivity between somatosensory and visual cortex in early...](https://pubmed.ncbi.nlm.nih.gov/15380014/)** > > Crossmodal plasticity occurs when loss of input in one sensory modality leads to reorganization in brain representations of other sensory modalities. In congenital blindness the visual cortex becomes responsive to somatosensory input such as occurs... Early inputs, different than what the brain was precisely evolved for, can repurpose functions in the brain. Be it reallocating motor cortex to serve six digits instead of five, or visual cortex responding to somatosensory input. In both cases early, during periods of brain plasticity, seems important. [Next page](https://boards.straightdope.com/t/polydactylism/976687.md?page=2)