Does thumb posture influence the mental rotation of hands?

Area of Science:

• Cognitive Neuroscience
• Human Motor Control

Background:

• Thumb posture plays a crucial role in manual actions but its influence on mental rotation remains understudied.
• Understanding how thumb posture affects sensory contributions is key to deciphering hand laterality judgments.

Purpose of the Study:

• To investigate whether thumb posture modulates the interplay between visual and proprioceptive inputs during mental rotation.
• To determine if experimentally fixing thumb posture influences performance in hand laterality judgment tasks.

Main Methods:

• Two experiments were conducted using hand laterality judgment tasks with identical stimuli (left/right hands, palmar/dorsal views, four orientations).
• Stimuli varied in thumb posture: either extended digits or thumb flexed into the palm.
• In Experiment 2, participants' thumbs were physically taped in a flexed posture before and during the task.

Main Results:

• Reaction times were affected by stimulus orientation, hand side, and view in both experiments.
• A significant effect of stimulus thumb posture on reaction time was observed only in Experiment 2, where thumbs were fixed.
• Palmar view stimuli rotated 90° towards the midline yielded faster reaction times than those rotated away, suggesting differential strategy use.

Conclusions:

• Thumb posture significantly influences mental rotation performance, particularly when experimentally constrained.
• The findings suggest that participants utilize motor imagery for palmar hand views but not dorsal views.
• This indicates distinct visual and sensorimotor familiarity associated with different hand postures and views.