People’s capacity to judge an object's distance, particularly in low light, is linked to their height. Taller individuals, on average, are better at doing so. Besides giving the vertically privileged yet another reason to feel smug, the study could improve our understanding of the human visual system.
There is a mystery at the heart of the way we process the light our eyes take in. In Science Advances, a team led by Professor Zijiang He of Louisville University put it this way: “This ability is especially fascinating because the optical images of natural scenes that project into our eyes are insufficient to adequately form a perceptual space.” In other words, we don’t know what the steps are between seeing the world around us and working out where things are in relation to each other, or to us.
The brain appears to have some pre-existing knowledge it uses to interpret what we see, presumably built up over a lifetime of operating, but we have a poor grasp of what this is and where it comes from.
Zijiang He had subjects judge the location of a dimly lit target and, after it had been removed, had them walk to where they remembered it being and estimate the height with their hands.
Some of the findings were unsurprising. Intrinsic knowledge is more important when light is low or there is a shortage of background cues. We are also better at placing an object in relation to the ground than the ceiling, apparently because most of us are used to living in rooms where the ceiling is closer to our eyes than the floor, when standing.
The headline observation, however, was that tall people are simply better at working out objects' locations, and their advantage increases in low light. This isn’t just a matter of gaining perspective by being further from the reference point on the ground. He had people sit on chairs and stand on boxes so their eyes were on the same level, and those of greater stature retained an advantage.
Both tall and short people perceived objects in the dark as being closer than they were, but short people were out by more (G) Zhou et al, Science Advances.
He's sample size, just 12 tall and 12 short people, may be undersized to draw conclusions with too much confidence, but the findings fit the authors' hypothesis: “An individual's accumulated lifetimes experiences of being tall and his or her constant interactions with ground-based objects not only determine intrinsic spatial knowledge, but also endow him or her with an advantage in spatial ability in the intermediate distance range.”
The theory is that throughout our lives we see objects and get used to automatically estimating height and distance. In the absence of clear cues, these estimates are probabilistic. When looking at objects close to the ground, tall people come at it from a different angle to their shorter counterparts, which has served as a better practice.
As if higher salaries and longer lifespans were not enough, it seems tall people are just determined to have all the advantages. Maybe Randy Newman had a point.