Mind Hacks

Hack #77. See a Person in Moving Lights

Lights on the joints of a walking person are enough to give a vivid impression of the person, carrying information on mood, gender, and other details—but only while the person keeps moving.

Visual perception has special routines for grouping things that move along together into single objects [[Hack #76]]. That’s why we see cars as cars and not a collection of wheels, glass, and side-view mirrors just happening to travel along in the same direction. That’s all well and good, but humans live not just in a world of objects like trees and cars, but a world full of people. Given how social we are, and how tricky other people can be, it’s not surprising we also have specialized routines for grouping things that move like people together into single objects too. Looking at only a constellation of moving points of light attached to knees, elbows, and other parts of the body, we get a vivid perception of a person, a perception that doesn’t exist at all when the points of light are still.

In Action

Open up your browser and point it at http://www.lifesci.sussex.ac.uk/home/George_Mather/Motion/BM.HTML ¹ or http://www.at-bristol.org.uk/Optical/DancingLights_main.htm (both are QuickTime movies). What do you see?

Both are just points of light moving in two dimensions. Yet the first is clearly a person walking, and the second obviously two people dancing, fighting, and otherwise performing.

As with the common fate demos [[Hack #76]] of how we group objects ...