Asymmetrical representation of body orientation

Area of Science:

• Neuroscience
• Perception
• Human factors

Background:

• A consistent leftward bias exists in the perception of object orientation, gravity, and body position.
• The origins of this leftward bias, whether in sensory input or processing, remain unclear for vestibular, visual, and somatosensory cues.

Purpose of the Study:

• To directly investigate whether a leftward bias in perceived orientation arises from sensory or processing differences.
• To determine the specific sensory modality contributing to the perceived upright (PU) bias.

Main Methods:

• Participants completed the Oriented Character Recognition Test (OCHART).
• Body posture and visual orientation cues were manipulated relative to gravity.
• Response patterns were analyzed for asymmetries based on body tilt (left-side-down vs. right-side-down).

Main Results:

• Response patterns differed systematically based on the direction of body tilt.
• A leftward asymmetry in perceived upright (PU) was identified.
• This asymmetry was best explained by a 5.6° leftward bias in the perceived body orientation relative to the head.

Conclusions:

• The perceived upright bias is not symmetrical and is influenced by body orientation.
• The findings suggest a specific contribution of body sense, particularly perceived body orientation, to the leftward bias.
• This aligns with other observed left-leaning asymmetries in sensory perception and posture.