Visual proprioceptive control of standing in human infants Visual proprioceptive control of standing in human infants David N. Lee & Eric Aronson By: Vannida Lorn

Background Three important receptor systems: 1. Exteroception – stimuli outside the body 2. Proprioception – position of the body 3. Interception – stimuli inside the body

Traditional View of Standing Standing requires constant muscle adjustments Ideal position is vertical Movement away from vertical causes lost of balance Standing involves proprioception because you use mechanoreceptors

However… Physical influence on standing, but what about visual influence? Vision not only exteroceptive, but also proprioceptive? Supporting Evidence: ◦ Wood’s (1895) “haunted swing” ◦ Edward (1946) and Witkin & Wapner’s (1950) blindfold experiment

Hypothesis Is visual proprioceptive information used in maintaining balance in standing?

Subjects: Human infants Baby Vannida!

Apparatus 3 walls and a ceiling, suspended with 4 ropes

Apparatus (cont.) Inside of the “room” was illuminated Pictures were hung to make it more cozy

Procedure Swayed the room forward (which should cause a backward sway in the infant) Swayed the room backward (which should cause a forward sway in the infant)

Conflict Visual proprioception calls for compensatory movement opposite of room movement BUT mechanical proprioception should counteract the compensatory sway …so if there is any abnormal loss of balance, this suggests that visual information dominated over mechanical information

Movement of room forward causing a feeling of a backward sway

Results 82% of responses resulted in a loss of balance ◦ 26% sway ◦ 23% stagger ◦ 33% fall Suggests Vision > Mechanics

Alternative Hypotheses 1. Avoidance response to a looming effect ◦ However, this only applies when the room swayed towards the infant 2. Flow of air from the swaying of the room caused the loss of balance ◦ Flow of air was so slight, unlikely to have been the cause of loss of balance

Conclusion For infants: visual proprioception > mechanical proprioception in maintaining posture Visual system matures quicker than the motor system During early life, visual proprioception is used to learn how to stand As we get older, with practice does our mechanical proprioception performs as efficient as vision.