BACKGROUND: People can focus on more than three items at a time if those items share a common color: Psychologists at Johns Hopkins University have demonstrated that when players wear uniforms, it allows spectators, players and coaches at major sporting events to overcome humans' natural limit of tracking no more than three objects at a time. The common color of uniforms allows them to overcome the usual limit because they perceive separate individuals as a single set.
ABOUT THE STUDY: The Hopkins researchers asked undergraduate volunteers to view series of colored dots flashing onto a black computer screen for about one half second – too fast to count the dots. The subjects were then asked to estimate the number of dots in one randomly selected set -- some of which contained as many as 35 dots -- on each trial. Half the time, the subjects were told in advance whether to pay attention to just the red dots, for example. Otherwise, the subjects were required to store as much information as possible in visual memory from what they saw briefly onscreen. They found that humans were unable to store information from more than three sets at once. However, dot counts were much more accurate when the given set contained three or fewer colors of dots.
SEEING IN COLOR: The human eye works in much the same way as a camera captures images on film. Its "film" is the retina, a thin layer of neural tissue lining the back of the eye, made of photoreceptor cells that receive light, and other cells that interpret this information and send the signal to the brain via the optic nerve. The retina contains two kinds of photoreceptor cells: cone cells and rod cells. Cone cells are sensitive to bright light and can perceive colors. The human eye has three types of cone cells, each sensitive to a particular primary color of light: blue, green and red. These three primary colors can mix in the eye so we can see more complex shades, such as violet or orange. Objects absorb some colors of light and reflect others, and this determines the colors that we see. When light hits a bright red apple, for instance, the apple’s surface absorbs all the wavelengths except red, which is reflected to the eye. So we perceive the apple as being red. In contrast, rod cells work best in low light and can perceive black and white images.
The Human Factors and Ergonomics Society contributed to the information contained in the TV portion of this report.