Investigating the uncanny valley for prosthetic hands

Abstract

People find prosthetic hands to be eerie, most consistently for less human-like prosthetic hands. This effect is not driven by ambiguity about whether to categorise the prosthetic hand as human or artificial. Clinical relevance More obviously artificial, less-realistic, prosthetic hands consistently generate a sense of eeriness, while more realistic prosthetic hands avoid the uncanny valley, at least on initial viewing. Thus, greater realism in prosthetic design may not always incur a cost, although the role of movement and cutaneous input requires further investigation.

Upper- and lower-limb amputees show reduced levels of eeriness for images of prosthetic hands

“…These different groups were examined due to their differing and dissociable levels of visual experience with, and practical use of, prosthetic hands. We expected the control group to broadly replicate the patterns found in the work of Poliakoff et al (2018), showing the strongest levels of unease for the unrealistic-looking covered prosthetic hands. We predicted that the upper-limb prosthesis users would be the least affected by the uncanny phenomenon, due to both their visual familiarity with the subjects of the images and the use of their own prosthetic limbs.…”

“…Our fourth group was 24 anatomically intact university students (12 male, mean age = 24.5 years, SD = 7.4) recruited from Liverpool Hope University, who had received 6 h training over a 2-week period in a visuomotor task using a BeBionic (Otto Bock HealthCare, Duderstadt, Germany) myoelectric prosthetic hand simulator (for details, see Parr, Vine, Harrison, & Wood, 2018). The final group consisted of 20 further anatomically intact university students (controls) recruited from Manchester Metropolitan University (13 male, mean age = 25.8 years, SD = 8.3), in a similar protocol to that outlined by Poliakoff et al (2018).…”

“…Participants rated the eeriness and human-likeness of the 12 photographic images shown in Fig. 1a of Poliakoff et al (2018). In brief, these images consist of three robotic hands (hereafter referred to as “mechanical”), three unrealistic-looking prosthetic hands, three realistic-looking prosthetic hands, and three anatomic human hands.…”

“…Despite these early suggestions, it is only recently that there have been empirical reports showing that participants rate life-like prosthetic hands to be eerier than either mechanical hands or anatomic human hands (Poliakoff, Beach, Best, Howard, & Gowen, 2013; Poliakoff, O’Kane, Carefoot, Kyberd, & Gowen, 2018). Both of these studies, however, have been undertaken in populations without any significant experience of upper-limb prostheses (i.e., university students), and no empirical work has examined the degree to which prosthetic limb users experience this phenomenon.…”

“…Second, we hoped to further the understanding of how different types and extents of practical experience with prostheses might affect the uncanny phenomenon in a range of populations, including groups with limb absence and anatomically intact groups. To this end, we used the hand stimuli developed by Poliakoff et al (2018) to examine ratings of eeriness and human-likeness in upper-limb prosthesis users, lower-limb prosthesis users, prosthetists (individuals who are involved in fitting prosthetic limbs), anatomically intact controls using their anatomic limb, and anatomically intact controls using an upper-limb prosthesis simulator on which they had received extensive training. These different groups were examined due to their differing and dissociable levels of visual experience with, and practical use of, prosthetic hands.…”