If someone, somewhere hadn't thought to make team
uniforms the same color, we might be stuck watching NBA
finals or World Cup soccer matches with only two players
and a ref.
It is that color coding, Johns Hopkins psychologists
have now demonstrated, that allows spectators, players and
coaches at sporting events to overcome humans' natural
limit of tracking no more than three objects at a time.
"We've known for some time that human beings are
limited to paying attention to no more than three objects
at any one time," said Justin Halberda, assistant professor
of psychological and
brain sciences in the Zanvyl Krieger School of Arts and
"We report the rather surprising result that people
can focus on more than three items at a time if those items
share a common color," said Halberda, who collaborated on
the research with Lisa Feigenson, also an assistant
professor of psychological and brain sciences at Johns
Hopkins. "Our research suggests that the common color
allows people to overcome the usual limit because the
'color coding' enables them to perceive the separate
individuals as a single set."
Thus: Miami Heat fans perceive their five
white-jerseyed players as a unit in action against five
blue-shirted Dallas Mavericks. England's football faithful
can track their white-shirted field players against
Sweden's yellow-garbed 10. (Since soccer goalies wear
different colors than field players, though, fans of both
clubs may have to think a moment before remembering which
keeper goes with which team.)
The color-sorting ability comes in handy not just in
sports. Poker players get a feel for the size of the pot by
checking out different colored chips. A glance in the
cooler tells a picnic organizer whether she has the right
mix of red Coke and blue Pepsi cans.
Knowing that color is the key to making sense of large
numbers of objects "informs our understanding of the
structure of visual cognition and reveals that humans rely
on early visual features to attend large sets in parallel,"
Halberda said. "Ongoing work in our lab is revealing which
other features humans might use."
Halberda and Feigenson reached their conclusion by
asking Johns Hopkins undergraduate volunteers to view
series of colored dots flashing onto a black computer
screen. The subjects were asked to estimate the number of
dots in one randomly selected set on each trial.
Half the time, the subjects were told in advance
whether to pay attention to, say, just the red dots or just
the green ones. Otherwise, the subjects were required to
store as much information as possible in visual memory from
what they saw briefly onscreen.
Subjects viewed the sets, some containing as many as
35 dots, for less than half a second, which Halberda points
out "is too short to allow the subjects to actually count
the dots." Subjects were very accurate when told in advance
which set to pay attention to, regardless of how many
different colors were present, revealing that humans are
able to select a set that shares a common color. Subjects
were also very accurate at enumerating a color subset when
asked after the flash of dots so long as the flash
contained no more than three colors.
"We found that humans are unable to store information
from more than three sets at once," Halberda said. "This
places an important constraint on how humans think about
and interact with sets in the world."
Johns Hopkins University and the National Institutes
of Health provided funding for this study, which is
reported in the July issue of Psychological