If there is an association between black and aggression then teams wearing black
should be penalized more than would be expected simply by chance. And they were.
Teams with black uniforms, such as Oakland, Chicago, and Cincinnati in the NFL, and
Philadelphia, Pittsburgh, and Vancouver in the NHL, were reliably more aggressive than
many other teams. The investigators also examined the archives for penalty records of
any teams that switched their uniform color from nonblack to black sometime during the
period under observation. An interesting question is whether a team that switches from
nonblack to black becomes more aggressive after it starts wearing black. The analysis
of the archival data suggested that this indeed was the case. Data provided by two NHL
teams revealed that when these teams donned black uniforms they were penalized
more. In addition, one team in the NHL that switched from a nonblack color to a
different nonblack color did not show any increase in aggressiveness. This latter finding
helps to rule out an effect of simply switching uniforms, as, for example, might occur if
players compete more energetically after any change.