Can looking at a hand make your skin crawl? - Poliakoff E. et al, 2013 [review]

There is a new study out by Ellen Poliakoff [1] (Press release [link], article [link]). As someone like me who has gone on about appearances of my prosthetic hands quite a bit, this of course is interesting! So here is the study (Poliakoff et al. (2013) [PDF]) and here is the review.


It is postulated that there is an uncanny valley, whereby human-like stimuli such as robots or animated characters that fall short of being fully human are perceived as eerie or unsettling. Previous research has explored the existence of this effect for faces and whole bodies, while here we explore responses to photographs of real and artificial hands. In keeping with the notion of an uncanny valley, prosthetic hands that were of intermediate human-likeness were given the highest ratings of eeriness. However, within the categories of hands, ratings of eeriness reduced as human-likeness increased, suggesting a more complex pattern. Further investigation of this effect will be of relevance to the design of prosthetic limbs and could be used to test theories of the uncanny valley and social perception with simple stimuli.

Who was first with this?


"The research to date has used faces or whole bodies, and here we investigate for the first time an uncanny valley for hand stimuli. This is not only of theoretical interest, but also has implications for the design of prosthetics."


That this is the first research being done using hand stimuli really is a bold claim, however, it is untrue. On two acccounts:

  • they were not first, and
  • they did not use hand stimuli

The first very intentionally designed non-human surface appearance of a shape resembling a human hand in still images but also approximating one in motion should probably go back to Jacques Monestier, and the hand is called the Monestier hand (published here on December 2nd, 2009, four years ago). The research that went into that result has been done by Lescoeur and Monestier, we have to presume.

Then there was Otto Bock's patented Michelangelo hand glove (USD595854 and CA122162S) designed by Peter Kuschnigg (July 7th, 2009). This remained a prosthetic design no one wore at the time, simply because Otto Bock was unable to roll out any usable prototypes - not until years later.

The first person to systematically go out and use an intentional mix of "human shape" (by wearing a prosthetic hand rather than a hook device) and "non-human surface appearance"(by varying that through different means) in a researching manner, across a whole range of appearances, that was me.

I was doing that at a time when Bertolt Meyer (we went for a beer where he saw my still freshly painted Becker red hand live on September 2nd, 2009, way before he started telling everybody how much he liked non-human appearances in his prosthetic arm such as on a TV show somewhere between April 15th and June 24th 2011) still tried to get an extremely life-like silicone hand glove, and when the pinnacle of prosthetic hand and arm existence contained a manually copied and painted surface appearance of the remaining limb (Pillet silicone arms range around 30'000 Euro).

The person to spearhead aggressive non-human surface experiments on a wider scale was me all along, and no one else. Sorry to say guys, if you want things done earlier you have to get up earlier.

It was me who literally single-handedly came up with the bold non-human color combined with human shapes, and who charged forward with a series of experiments up to talking Centri into actually fabricating small series of these (link below), and, getting my prostetist to get the Swiss importer into getting a transparent version (see Phantom hand, below).

Let us recap.

I was the only lone person to go entirely ballistic with color and shape variation when I started in 2008/9. Then, "maximal cosmetic alignment" with "natural skin" was still regarded as the pinnacle of upper extremity prosthetics.

My line of research was web-published all along, under the "Red Hand Series / Technical Design Series" category. More concisely, we find:

Other attempts to do the same were published later without any reference to my works.

  • In autumn 2009, Joanne Tilley and Magnus Feil started a prosthetic arm series with their design students.
  • Dan Horkey came forward with getting the name of GTOPI out (October 14th, 2009). We were on the phone also to discuss particular appearances. Since then, chromed sockets appear to be very much en vogue.
  • Spare Parts art exhibitions of colored artworks on prosthetic legs (Priscilla Sutton, Brisbane 2010 and London 2012).
  • A German prosthetist, Frank Purk, started to publish his works starting in 2011 (link).
  • OpenProsthetics, OpenBionics and whoever else now promote colored, at times red, hands. This was not their invention though.

My concept studies helped to inspire a range of follow-up experiments that actually referenced it:

  • Super Prosthetics project by Becky Pilditch, Graduation Show 2010, category "Innovation Design Engineering", Royal College of Art, London, United Kingdom of Great Britain (first mail and mention of Red Hand series November 2nd 2009, read here published January 23rd, 2010).
  • APART diploma design thesis, 2012, by Doreen Haedicke, was only in part inspired by the Red Hand experiment, however initially there was interest in referencing some of the Red Hand design (link).
  • ArmWear - Cool Prosthetics - Graduation Report September 2010, Delft University of Technology, The Netherlands (review published here October 29th, 2013) [2].

I am not saying that I once thought about something and kept it to myself.

I am saying that we all worked our butts off to get somewhere with this. There is sweat behind this here. The amount of footwork I did using real prosthetic hands in a real 3D world that we live in is quite considerable.

To then say that hand stimuli as typed up by Poliakoff et al. (2013) would be the first experiment ever in relation to prosthetic hand appearance research, that is simply wrong.

You need to reference all of us here, you really would want to do that. And you need to use prosthetic hand stimuli. Not photography.

Hand versus simulacra


  • "Overall, we have demonstrated that prosthetic hands that fall short of being human are rated as being eerie."
  • "(Title) Can looking at a hand make your skin crawl? Peering into the uncanny valley for hands. "


The authors demonstrated that a number of viewers found still photos of prosthetic hands eerie. Still photos. Not prosthetic hands. There is a massive difference! A prosthetic hand is one if you can also squeeze yourself with it. A pipe is one if you can smoke it (check Magritte!).

With that mix-up or confusion, the authors prove that they are lost within the various levels of facsimile her. And in the context of prosthetic hands, I would argue that error is conceptually fatal.

The Krukenberg arm - another option to consider for below elbow amputees - is one of the most underused options, quite simply because it looks horrible on still photos. It does not look horrible in real life, animated, dynamically used - conversely, people with Krukenberg arms tend to get positive compliments, and the vast majority is very happy with these [3] (they have staggering acceptance rates over 90%, which strongly contrasts with all time low prosthetic arm rejection rates). With a Krukenberg arm costing some 15'000 to 18'000 CHF for decades of 24/7 grip function with a very high quality and a prosthetic arm running up some 300'000 to 700'000 CHF over decades of maintenance with a relatively limited function, that visual and analytical error - confusing still photo rating with "actual ratings" - costs our insurances millions of dollars that are, technically speaking, wasted.

Just because researchers and doctors cannot wrap their head around various levels of estrangement, and simply because a fear of disabled people seems to make them prefer photographs over the real people, does not lick the uncomfortable reality away that realities are, photos are not. Particularly in upper extremity appearances.

A rather uncritical aspect here [1] also becomes apparent when considering the prosthetic hand photographs (Figure 1, middle [1]).

Did you realize that the black background (photos 1,2,3,4,5, 6 [1]) correlated with a considerably eerier score (figures drawn from diagram: 5,6 +/- 0,8 [1]) than the white background (4,2 +/- 1,1 [1]). In other words, as photo motive, I and my hosed arm seem to look better with white than with black.

Fitting a logistic regression curve with data taken directly from the study [1] and feeding through my own statistics (see diagram below, whole model test p=0.0401, SAS JMP) results in a correlation whereas for prosthetic hand photos, a white background has a > 90% chance of yielding eeriness scores below ~3,4, whereas a black background has a >90% chance of effecting an eeriness score above ~6.


So the missing distinction between "hand"and "photo of a hand" has a measurable significant impact on the results. When evaluating still photos, background color can (statistically significantly!) impact the result you would wish to get from the hand appearance only.

This is probably well known throughout the industry.

Current prosthetic hand webpages and advertising (including such expensive attempts such as Touchbionics' iLimb, Otto Bock's Michelangelo or RSL Steeper's BeBionic) all demonstrate their products on white backgrounds (with the notable exception of the Monestier hand design, which also makes "prosthetic hands" look good in front of black backgrounds).

Besides, prosthetic hand constructors these days work with trying to get the dynamics of hands right, that much more than their photographic appearance. Also, the impact of robotic hand motion has been studied already [4].

What prosthetic hands, exactly, were used?


"Therefore, we obtained ratings of photographic images of real, prosthetic, and mechanical hands."


Actual prosthetic hands are (a) passive / cosmetic, (b) body powered or (c) myoelectric.

That is a distinction that is known for decades, and those are prosthetic options that are being built since decades. This study waltzes over this fact and neither declares make, brand, nor choice for a particular hand's appearance. Due to lacking standards in appearance of these hands (ambient versus specular light, angle, et cetera), we cannot know how shininess, surface structure and other aspects impacted the eeriness that may be perceived when really facing one of these hands.

Also, current prosthetic hands can be equipped with non-human surface options both as part of stock orders or as part of customization. I get my custom colored PVC gloves made by Centri (Sweden) - also a well publicized fact that is accessible for anyone that cares to look for it.

So restricting one's perceptive research to ill-defined photographs that lack current scope, that lack technical description, that lack comparable definiton for photographic aspects, that strikes me as not so interesting. Furthermore, customer-side interventions, whether self made (such as my own test series, see above) or customization professionals (Dan Horkey of GTOPI, to name the obvious) are well established and well known if not infamous throughout amputee communities.

Wrap up

Also and after examining the above mentioned issues, this study shows (again) that

  • academic research continues to be somewhat pointless when related to the appearance of prosthetic arms despite several attempts to point it out to researchers that they are indeed living in their own bubble (as long they do not stop to live in their own bubble, that is), so academic studies such as continue to be mysterious, strange, unexpected, sending a chill up my spine; meantime, I wrote testing requirements also for appearance (link) and subsequently was invited to publish a commentary regarding test requirements in the leading commercial journal (link).
  • existing prosthetic hand test series and their anecdotal results from real experience are happily ignored by academic researchers


[1] E. Poliakoff, N. Beach, R. Best, T. Howard, and E. Gowen, "Can looking at a hand make your skin crawl? Peering into the uncanny valley for hands," Perception, vol. 42, pp. 998-1000, 2013.
  title={{Can looking at a hand make your skin crawl? Peering into the uncanny valley for hands}},
  author={Poliakoff, Ellen and Beach, Natalie and Best, Rebecca and Howard, Toby and Gowen, Emma},
[2] M. Geurts, "Armwear: Cool Prosthetics (Graduation report)," Delft University of Technology, Delft, The Netherlands, 2010.
    author = {Geurts, Marijn},
     month = {September},
     title = {{Armwear: Cool Prosthetics (Graduation report)}},
      year = {2010},
    journal = {{Delft University of Technology, Delft, The Netherlands}},
[3] R. Baumgartner and C. Asey, "[Indications for the Krukenberg hand based on long-term results]," Z Orthop Ihre Grenzgeb, vol. 132, iss. 3, pp. 180-184, 1994.
   Author="Baumgartner, R.  and Asey, C. ",
   Title="{{[{I}ndications for the {K}rukenberg hand based on long-term results]}}",
   Journal={{Z Orthop Ihre Grenzgeb}},
[4] [doi] C. Press, G. Bird, R. Flach, and C. Heyes, "Robotic movement elicits automatic imitation ," Cognitive Brain Research, vol. 25, iss. 3, pp. 632-640, 2005.
title = "Robotic movement elicits automatic imitation ",
journal = {{Cognitive Brain Research}},
volume = "25",
number = "3",
pages = "632 - 640",
year = "2005",
note = "",
issn = "0926-6410",
doi = "",
url = "",
author = "Clare Press and Geoffrey Bird and Rüdiger Flach and Cecilia Heyes",
keywords = "Action observation",
keywords = "Imitation",
keywords = "Learning",
keywords = "Mirror-neuron system",
keywords = "Visuomotor priming",
keywords = "Stimulus–response compatibility "

Cite this article:
Wolf Schweitzer: - Can looking at a hand make your skin crawl? - Poliakoff E. et al, 2013 [review]; published 13/11/2013, 15:33; URL:

BibTeX: @MISC{schweitzer_wolf_1638807747, author = {Wolf Schweitzer}, title = {{ - Can looking at a hand make your skin crawl? - Poliakoff E. et al, 2013 [review]}}, month = {November}, year = {2013}, url = {} }