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Why can’t we walk straight ahead?

In 1926, American proto-zoologist Asa Schaeffer sat a nine year old boy in a car, blindfolded him, and asked him to drive straight ahead into the prairie in western Kansas. He (luckily?) did this for scientific reasons. But what did he try to find out?

In previous experiments, Schaeffer had observed that people were unable to walk in a straight line when blindfolded. Even over short distances, they would rather move in spirals. Schaeffer suspected all sorts of physiologic reasons from different leg-lengths to the influence of body axis, and began to systematically rule them out: He had study participants walk under different circumstances, swim and row – blindfolded – and that is also why poor nine-year-old subject “U” mentioned above had to go on his worrisome ride. But the result was always the same: round and round and round they went – all the while thinking they were walking in a perfectly straight line. In 2009, Jan Souman and his Team at the Max Planck Institute for Biological Cybernetics had people walk in the Sahara desert, the German woods, and on the beach, coming to the same conclusion as Schaeffer in the 1920s (with much fancier measures than Schaeffer’s pen-and-paper tracking, of course): without a visual focus point like the sun we go around in spirals. But: why? After negatively testing several physiological explanations like left or right handedness or different dopamine spitting of left and right brain sides, Souman assumes a random accumulation of “noise” in the sensorimotor system behind our tendency to go astray.

Is there, or can there be a systematic explanation to this puzzling observation? Can our tendency to walk in circles when deprived of vision even be considered an error? And if not – what might its function be?

More info:

Schaeffer, Asa: Spiral Movement in Man. Journal of Morphology and Physiology 45 (1928)

Tobias Boll