Perceiving and mentally rotating real and artificial hands

Introduction

In a hand laterality judgment task, participants determine whether rotated images depict a left or a right hand. It is believed that people use motor imagery (imagining their own body moving) to complete this task. This is evidenced by a biomechanical constraints effect (BCE), whereby people take longer to respond to hands shown at biologically awkward angles. It is unknown whether this extends to artificial hands. This study investigated whether prosthetic hands are processed differently when mentally manipulated, potentially due to their perceived eeriness.

Materials and Methods

In two online studies, participants completed a hand laterality judgment task containing real and artificial hands (realistic and mechanical prosthetics).

Results

All three hand types produced a BCE, evidencing motor imagery, although this was weaker in mechanical hands. Reaction time and slope (effect of angular rotation on reaction time) also varied between the hand types.

Conclusions

Our findings indicate that people use motor imagery to process artificial hands, although possible differences in processing between the hands should be followed up.

Clinical Relevance

Hand laterality judgment tasks could be used to further explore differences in how people process real and artificial hands. Future research might incorporate these tasks with users of prosthetic hands.