Handedness in the Mental Rotation of Hands

With Elizabeth R. Chrastil, Mary Hegarty

Ninety percent of human beings are right-handed. Accordingly, the world has been designed for right-handed use. But could spatial abilities be affected by knowledge of this right-handed world? If so, how does this world knowledge weigh against a person’s own embodied experience of their dominant hand when it comes to spatial thinking? Many psychologists tend to recruit only right-handed participants, but testing right-handed subjects alone cannot solve this puzzle, because their embodiment and world knowledge are indistinguishable. Since we all live in a right-handed world, we must test left-handed people to determine whether their spatial thinking diverges from that of right-handers. The mental rotation of hands shows a very different pattern of response from that of other mental rotation tasks (MRTs); the reason for this result has been assumed to be familiarity with hands. Thus, mental rotation of hands is a good candidate for testing whether embodiment or world knowledge influences spatial thinking.

In the current study, we conducted a hand MRT in both left-handed and right-handed groups. Our findings demonstrate that embodied experience influences spatial thinking about right hands, which might account for the presence of world knowledge variability in MRT, while also suggesting that common external experience shapes performance in spatial thinking tasks. These findings demonstrate that investigations in spatial thinking tasks might overlook the nuances reflecting world knowledge versus embodied experience if researchers do not recruit left-handers.

Relevant resources:

• Cheng, Y., Hegarty, M., & Chrastil, E. R. (2020). Telling right from right: the influence of handedness in the mental rotation of hands. Cognitive Research: Principles and Implications, 5, 1-18. [pdf]

• Cheng, Y. . Left Hand, Right Hand. 2018 Spatial Lightning Talks, UCSB Center for Spatial Studies, Santa Barbara. Feb., 2018. [video]